diff --git a/NullDepth.slnx b/NullDepth.slnx
index dab69e9..eaffa1b 100644
--- a/NullDepth.slnx
+++ b/NullDepth.slnx
@@ -2,4 +2,7 @@
   <Folder Name="/src/">
     <Project Path="src/NullDepth/NullDepth.csproj" />
   </Folder>
+  <Folder Name="/tests/">
+    <Project Path="tests/NullDepth.Validation/NullDepth.Validation.csproj" />
+  </Folder>
 </Solution>
diff --git a/README.md b/README.md
index 1d0a542..ba1ecf2 100644
--- a/README.md
+++ b/README.md
@@ -31,4 +31,12 @@ Build celej solution:
 dotnet build NullDepth.slnx -c Release
 ```
 
+Automatická kontrola dát a všetkých hlavných herných ciest:
+
+```powershell
+dotnet run --project tests\NullDepth.Validation\NullDepth.Validation.csproj -c Release
+```
+
 Herný obsah upravíte v `src/NullDepth/wwwroot/data/game.json`; slovenské a anglické texty sú v `src/NullDepth/wwwroot/localization`.
+
+Aktuálny prototyp obsahuje archív nájdených logov, dátovo definovaný inventár, fade a alarm prechody, autosave indikátor, potvrdenie novej hry, mazanie save a migráciu starších uložených dát.
diff --git a/specs/NULL_DEPTH_TECHNICAL_ARCHITECTURE.md b/specs/NULL_DEPTH_TECHNICAL_ARCHITECTURE.md
index 8f07dde..69c2228 100644
--- a/specs/NULL_DEPTH_TECHNICAL_ARCHITECTURE.md
+++ b/specs/NULL_DEPTH_TECHNICAL_ARCHITECTURE.md
@@ -7,6 +7,8 @@
 - HTML/CSS fullscreen UI
 - JSON obsah bez backendu a databázy
 - browser localStorage pre save a settings
+- Web Audio/HTML Audio vrstva s procedurálnym fallbackom
+- Browser Fullscreen API ovládané zo Settings
 
 ## Princíp
 
@@ -24,13 +26,16 @@ Input / kliknutie
 
 ```text
 Game/GameService.cs                  načítanie dát, pohyb, flagy, save
+Game/AudioService.cs                 ambienty, SFX a live master volume
 Models/GameModels.cs                dátové modely
 Pages/Home.razor                    fullscreen obrazovky a overlaye
+wwwroot/js/null-depth.js             audio runtime a fullscreen interop
 wwwroot/data/game.json              celý level a gameplay obsah
 wwwroot/localization/sk.json        slovenské texty
 wwwroot/localization/en.json        anglické texty
 wwwroot/assets/images/...           title a miestnosti
 wwwroot/assets/audio/...            ambience a SFX sloty
+tests/NullDepth.Validation          offline dátové a gameplay testy
 ```
 
 ## RoomDefinition
@@ -42,13 +47,22 @@ Interakcia môže:
 - vyžadovať alebo zakazovať flagy
 - nastaviť flagy
 - pridať predmet
+- uložiť nájdený záznam do trvalého archívu
 - vytvoriť checkpoint
 - ponúknuť dátové voľby
 - spustiť smrť alebo ending
 
 ## GameState
 
-Ukladá aktuálnu miestnosť, navštívené miestnosti, flagy, inventár, checkpoint a čas uloženia. Save používa kľúč `null-depth.save.v1`; settings používajú `null-depth.settings.v1`.
+Ukladá aktuálnu miestnosť, navštívené miestnosti, flagy, inventár, archív logov, checkpoint, dokončený ending a čas uloženia. Save používa kľúč `null-depth.save.v1`, ale vnútorná verzia stavu je `3` a starší stav sa automaticky migruje. Settings používajú `null-depth.settings.v1`.
+
+Nová hra pred prepísaním vyžaduje potvrdenie. Save možno vymazať v Settings. Poškodený alebo budúcou verziou nekompatibilný stav sa nikdy automaticky neprepíše; UI ponúkne jeho explicitné odstránenie.
+
+Ak je v miestnosti viac dostupných interakcií, `E` otvorí dátovo naplnený picker. Ovláda sa šípkami, Enterom, číslicami alebo myšou.
+
+Pohyb používa krátky fade, dôležité systémové zásahy alarmové bliknutie a text miestnosti jemný reveal. Každý zápis stavu vyvolá viditeľný autosave indikátor.
+
+`game.json` definuje aj `items`, `initialItems` a `archive`. Interakcia s `archiveId` pridá záznam do hráčovho archívu a ten zostáva dostupný cez `L` aj po zmiznutí jednorazovej interakcie.
 
 ## Rozšírenie hry
 
diff --git a/src/NullDepth/Game/AudioService.cs b/src/NullDepth/Game/AudioService.cs
new file mode 100644
index 0000000..085cede
--- /dev/null
+++ b/src/NullDepth/Game/AudioService.cs
@@ -0,0 +1,21 @@
+using Microsoft.JSInterop;
+
+namespace NullDepth.Game;
+
+public sealed class AudioService(IJSRuntime js)
+{
+    public async ValueTask InitializeAsync(int volume) =>
+        await js.InvokeVoidAsync("nullDepth.audio.initialize", volume);
+
+    public async ValueTask SetVolumeAsync(int volume) =>
+        await js.InvokeVoidAsync("nullDepth.audio.setMasterVolume", volume);
+
+    public async ValueTask PlayAmbientAsync(string? source) =>
+        await js.InvokeVoidAsync("nullDepth.audio.playAmbient", source);
+
+    public async ValueTask PlaySfxAsync(string? source) =>
+        await js.InvokeVoidAsync("nullDepth.audio.playSfx", source);
+
+    public async ValueTask StopAsync() =>
+        await js.InvokeVoidAsync("nullDepth.audio.stopAll");
+}
diff --git a/src/NullDepth/Game/GameService.cs b/src/NullDepth/Game/GameService.cs
index 0d7ad58..f11da73 100644
--- a/src/NullDepth/Game/GameService.cs
+++ b/src/NullDepth/Game/GameService.cs
@@ -7,6 +7,7 @@ namespace NullDepth.Game;
 
 public sealed class GameService(HttpClient http, IJSRuntime js)
 {
+    private const int CurrentSaveVersion = 3;
     private const string SaveKey = "null-depth.save.v1";
     private const string SettingsKey = "null-depth.settings.v1";
     private readonly JsonSerializerOptions _json = new(JsonSerializerDefaults.Web);
@@ -16,6 +17,8 @@ public sealed class GameService(HttpClient http, IJSRuntime js)
     public GameState State { get; private set; } = new();
     public PlayerSettings Settings { get; private set; } = new();
     public bool HasSave { get; private set; }
+    public SaveLoadResult LastLoadResult { get; private set; } = SaveLoadResult.Missing;
+    public event Action? Saved;
 
     public async Task InitializeAsync()
     {
@@ -25,12 +28,16 @@ public sealed class GameService(HttpClient http, IJSRuntime js)
             Language = await js.InvokeAsync<string>("nullDepth.browserLanguage")
         };
         await SetLanguageAsync(Settings.Language, persist: false);
-        HasSave = !string.IsNullOrWhiteSpace(await js.InvokeAsync<string?>("localStorage.getItem", SaveKey));
+        var rawSave = await js.InvokeAsync<string?>("localStorage.getItem", SaveKey);
+        HasSave = !string.IsNullOrWhiteSpace(rawSave);
+        LastLoadResult = InspectSave(rawSave);
     }
 
     public string T(string key) => _texts.TryGetValue(key, out var text) ? text : key;
     public RoomDefinition CurrentRoom => Data.Rooms.First(r => r.Id == State.CurrentRoomId);
     public RoomDefinition? FindRoom(string id) => Data.Rooms.FirstOrDefault(r => r.Id == id);
+    public ItemDefinition? FindItem(string id) => Data.Items.FirstOrDefault(i => i.Id == id);
+    public ArchiveDefinition? FindArchive(string id) => Data.Archive.FirstOrDefault(a => a.Id == id);
     public bool HasAll(IEnumerable<string> flags) => flags.All(State.Flags.Contains);
 
     public async Task SetLanguageAsync(string language, bool persist = true)
@@ -42,20 +49,92 @@ public sealed class GameService(HttpClient http, IJSRuntime js)
 
     public async Task NewGameAsync()
     {
-        State = new GameState { CurrentRoomId = Data.StartRoomId };
+        State = new GameState
+        {
+            CurrentRoomId = Data.StartRoomId,
+            ContentVersion = Data.Version,
+            Inventory = [.. Data.InitialItems]
+        };
         State.VisitedRooms.Add(State.CurrentRoomId);
         SetCheckpoint();
         await SaveAsync();
     }
 
-    public async Task<bool> ContinueAsync()
+    public async Task<SaveLoadResult> ContinueAsync()
     {
-        var loaded = await LoadValueAsync<GameState>(SaveKey);
-        if (loaded is null || FindRoom(loaded.CurrentRoomId) is null) return false;
+        var raw = await js.InvokeAsync<string?>("localStorage.getItem", SaveKey);
+        if (string.IsNullOrWhiteSpace(raw)) return LastLoadResult = SaveLoadResult.Missing;
+
+        GameState? loaded;
+        try { loaded = JsonSerializer.Deserialize<GameState>(raw, _json); }
+        catch { return LastLoadResult = SaveLoadResult.Corrupt; }
+        if (loaded is null) return LastLoadResult = SaveLoadResult.Corrupt;
+        if (loaded.Version > CurrentSaveVersion || loaded.ContentVersion > Data.Version)
+            return LastLoadResult = SaveLoadResult.Incompatible;
+
+        var migrated = loaded.Version < CurrentSaveVersion || loaded.ContentVersion < Data.Version;
+        Migrate(loaded);
         State = loaded;
         State.VisitedRooms.Add(State.CurrentRoomId);
-        HasSave = true;
-        return true;
+        if (migrated) await SaveAsync();
+        else HasSave = true;
+        return LastLoadResult = SaveLoadResult.Success;
+    }
+
+    private void Migrate(GameState state)
+    {
+        state.VisitedRooms ??= [];
+        state.Flags ??= [];
+        state.Inventory ??= [];
+        state.Archive ??= [];
+
+        if (state.Version < 2)
+        {
+            if (state.Flags.Contains("elevator_cycle_complete")) state.Flags.Remove("elevator_stalled");
+            if (state.Flags.Contains("core_shutdown")) state.CompletedEnding = "shutdown";
+            else if (state.Flags.Contains("external_network_restored")) state.CompletedEnding = "release";
+            else if (state.Flags.Contains("containment_active")) state.CompletedEnding = "containment";
+        }
+
+        if (state.Version < 3)
+        {
+            foreach (var archive in Data.Archive.Where(a => state.Flags.Contains($"{a.Id}_found") ||
+                         (a.Id == "containment_record" && state.Flags.Contains("containment_seen"))))
+                if (!state.Archive.Contains(archive.Id)) state.Archive.Add(archive.Id);
+            foreach (var item in Data.InitialItems)
+                if (!state.Inventory.Contains(item)) state.Inventory.Add(item);
+
+            if (state.Checkpoint is not null)
+            {
+                state.Checkpoint.VisitedRooms ??= [];
+                state.Checkpoint.Flags ??= [];
+                state.Checkpoint.Inventory ??= [];
+                state.Checkpoint.Archive ??= [];
+                foreach (var item in Data.InitialItems)
+                    if (!state.Checkpoint.Inventory.Contains(item)) state.Checkpoint.Inventory.Add(item);
+                foreach (var entry in Data.Archive.Where(a => state.Checkpoint.Flags.Contains($"{a.Id}_found") ||
+                             (a.Id == "containment_record" && state.Checkpoint.Flags.Contains("containment_seen"))))
+                    if (!state.Checkpoint.Archive.Contains(entry.Id)) state.Checkpoint.Archive.Add(entry.Id);
+            }
+        }
+
+        if (FindRoom(state.CurrentRoomId) is null) state.CurrentRoomId = Data.StartRoomId;
+        state.VisitedRooms.RemoveWhere(id => FindRoom(id) is null);
+        state.Inventory = state.Inventory.Where(id => FindItem(id) is not null).Distinct().ToList();
+        state.Archive = state.Archive.Where(id => FindArchive(id) is not null).Distinct().ToList();
+        if (state.Checkpoint is not null)
+        {
+            if (FindRoom(state.Checkpoint.RoomId) is null) state.Checkpoint.RoomId = Data.StartRoomId;
+            state.Checkpoint.VisitedRooms ??= [];
+            state.Checkpoint.Flags ??= [];
+            state.Checkpoint.Inventory ??= [];
+            state.Checkpoint.Archive ??= [];
+            state.Checkpoint.VisitedRooms.RemoveWhere(id => FindRoom(id) is null);
+            state.Checkpoint.Inventory = state.Checkpoint.Inventory.Where(id => FindItem(id) is not null).Distinct().ToList();
+            state.Checkpoint.Archive = state.Checkpoint.Archive.Where(id => FindArchive(id) is not null).Distinct().ToList();
+        }
+        state.Version = CurrentSaveVersion;
+        state.ContentVersion = Data.Version;
     }
 
     public async Task<string?> MoveAsync(string direction)
@@ -73,14 +152,17 @@ public sealed class GameService(HttpClient http, IJSRuntime js)
 
     public async Task ApplyInteractionAsync(InteractionDefinition interaction)
     {
-        Apply(interaction.SetFlags, interaction.AddItems);
+        Apply(interaction.SetFlags, interaction.ClearFlags, interaction.AddItems);
+        if (!string.IsNullOrWhiteSpace(interaction.ArchiveId) && !State.Archive.Contains(interaction.ArchiveId))
+            State.Archive.Add(interaction.ArchiveId);
         if (interaction.Checkpoint) SetCheckpoint();
         await SaveAsync();
     }
 
     public async Task ApplyChoiceAsync(ChoiceDefinition choice)
     {
-        Apply(choice.SetFlags, choice.AddItems);
+        Apply(choice.SetFlags, choice.ClearFlags, choice.AddItems);
+        if (!string.IsNullOrWhiteSpace(choice.Ending)) State.CompletedEnding = choice.Ending;
         if (choice.Checkpoint) SetCheckpoint();
         await SaveAsync();
     }
@@ -93,6 +175,8 @@ public sealed class GameService(HttpClient http, IJSRuntime js)
         State.VisitedRooms = [.. checkpoint.VisitedRooms];
         State.Flags = [.. checkpoint.Flags];
         State.Inventory = [.. checkpoint.Inventory];
+        State.Archive = [.. checkpoint.Archive];
+        State.CompletedEnding = null;
         await SaveAsync();
     }
 
@@ -108,10 +192,21 @@ public sealed class GameService(HttpClient http, IJSRuntime js)
         State.SavedAt = DateTimeOffset.UtcNow;
         await StoreValueAsync(SaveKey, State);
         HasSave = true;
+        LastLoadResult = SaveLoadResult.Success;
+        Saved?.Invoke();
     }
 
-    private void Apply(IEnumerable<string> flags, IEnumerable<string> items)
+    public async Task DeleteSaveAsync()
     {
+        await js.InvokeVoidAsync("localStorage.removeItem", SaveKey);
+        State = new GameState { CurrentRoomId = Data.StartRoomId, ContentVersion = Data.Version };
+        HasSave = false;
+        LastLoadResult = SaveLoadResult.Missing;
+    }
+
+    private void Apply(IEnumerable<string> flags, IEnumerable<string> clearFlags, IEnumerable<string> items)
+    {
+        foreach (var flag in clearFlags) State.Flags.Remove(flag);
         foreach (var flag in flags) State.Flags.Add(flag);
         foreach (var item in items) if (!State.Inventory.Contains(item)) State.Inventory.Add(item);
     }
@@ -121,9 +216,24 @@ public sealed class GameService(HttpClient http, IJSRuntime js)
         RoomId = State.CurrentRoomId,
         VisitedRooms = [.. State.VisitedRooms],
         Flags = [.. State.Flags],
-        Inventory = [.. State.Inventory]
+        Inventory = [.. State.Inventory],
+        Archive = [.. State.Archive]
     };
 
+    private SaveLoadResult InspectSave(string? raw)
+    {
+        if (string.IsNullOrWhiteSpace(raw)) return SaveLoadResult.Missing;
+        try
+        {
+            var save = JsonSerializer.Deserialize<GameState>(raw, _json);
+            if (save is null) return SaveLoadResult.Corrupt;
+            return save.Version > CurrentSaveVersion || save.ContentVersion > Data.Version
+                ? SaveLoadResult.Incompatible
+                : SaveLoadResult.Success;
+        }
+        catch { return SaveLoadResult.Corrupt; }
+    }
+
     private async Task<T?> LoadValueAsync<T>(string key)
     {
         var raw = await js.InvokeAsync<string?>("localStorage.getItem", key);
diff --git a/src/NullDepth/Models/GameModels.cs b/src/NullDepth/Models/GameModels.cs
index ae268d9..76cd5e9 100644
--- a/src/NullDepth/Models/GameModels.cs
+++ b/src/NullDepth/Models/GameModels.cs
@@ -2,16 +2,36 @@ namespace NullDepth.Models;
 
 public sealed class GameData
 {
+    public int Version { get; set; } = 1;
     public string StartRoomId { get; set; } = "loc_01_exterior_access";
+    public List<string> InitialItems { get; set; } = [];
+    public List<ItemDefinition> Items { get; set; } = [];
+    public List<ArchiveDefinition> Archive { get; set; } = [];
     public List<RoomDefinition> Rooms { get; set; } = [];
 }
 
+public sealed class ItemDefinition
+{
+    public string Id { get; set; } = "";
+    public string NameKey { get; set; } = "";
+    public string DescriptionKey { get; set; } = "";
+    public string Category { get; set; } = "equipment";
+}
+
+public sealed class ArchiveDefinition
+{
+    public string Id { get; set; } = "";
+    public string TitleKey { get; set; } = "";
+    public string ContentKey { get; set; } = "";
+}
+
 public sealed class RoomDefinition
 {
     public string Id { get; set; } = "";
     public string NameKey { get; set; } = "";
     public string DescriptionKey { get; set; } = "";
     public string Image { get; set; } = "";
+    public string? Ambient { get; set; }
     public string? AlternateImage { get; set; }
     public string? AlternateImageFlag { get; set; }
     public int X { get; set; }
@@ -36,7 +56,10 @@ public sealed class InteractionDefinition
     public List<string> RequiresFlags { get; set; } = [];
     public List<string> ForbiddenFlags { get; set; } = [];
     public List<string> SetFlags { get; set; } = [];
+    public List<string> ClearFlags { get; set; } = [];
     public List<string> AddItems { get; set; } = [];
+    public string? ArchiveId { get; set; }
+    public string? Sound { get; set; }
     public bool Checkpoint { get; set; }
     public List<ChoiceDefinition> Choices { get; set; } = [];
 }
@@ -47,7 +70,9 @@ public sealed class ChoiceDefinition
     public string? ResultKey { get; set; }
     public List<string> RequiresFlags { get; set; } = [];
     public List<string> SetFlags { get; set; } = [];
+    public List<string> ClearFlags { get; set; } = [];
     public List<string> AddItems { get; set; } = [];
+    public string? Sound { get; set; }
     public string? Ending { get; set; }
     public bool Death { get; set; }
     public bool Checkpoint { get; set; }
@@ -55,11 +80,14 @@ public sealed class ChoiceDefinition
 
 public sealed class GameState
 {
-    public int Version { get; set; } = 1;
+    public int Version { get; set; } = 3;
+    public int ContentVersion { get; set; } = 1;
     public string CurrentRoomId { get; set; } = "loc_01_exterior_access";
     public HashSet<string> VisitedRooms { get; set; } = [];
     public HashSet<string> Flags { get; set; } = [];
     public List<string> Inventory { get; set; } = [];
+    public List<string> Archive { get; set; } = [];
+    public string? CompletedEnding { get; set; }
     public GameSnapshot? Checkpoint { get; set; }
     public DateTimeOffset SavedAt { get; set; } = DateTimeOffset.UtcNow;
 }
@@ -70,6 +98,7 @@ public sealed class GameSnapshot
     public HashSet<string> VisitedRooms { get; set; } = [];
     public HashSet<string> Flags { get; set; } = [];
     public List<string> Inventory { get; set; } = [];
+    public List<string> Archive { get; set; } = [];
 }
 
 public sealed class PlayerSettings
@@ -77,3 +106,11 @@ public sealed class PlayerSettings
     public string Language { get; set; } = "en";
     public int MasterVolume { get; set; } = 70;
 }
+
+public enum SaveLoadResult
+{
+    Success,
+    Missing,
+    Corrupt,
+    Incompatible
+}
diff --git a/src/NullDepth/Pages/Home.razor b/src/NullDepth/Pages/Home.razor
index de3d6d7..e3690a0 100644
--- a/src/NullDepth/Pages/Home.razor
+++ b/src/NullDepth/Pages/Home.razor
@@ -1,9 +1,12 @@
 @page "/"
 @inject GameService Game
+@inject AudioService Audio
+@inject IJSRuntime JS
+@implements IDisposable
 
 <PageTitle>NULL DEPTH</PageTitle>
 
-<main class="game-shell" tabindex="0" @ref="_shell" @onkeydown="HandleKey" @onkeydown:preventDefault>
+<main class="game-shell @(_isTransitioning ? "transitioning" : "") @(_systemFlash ? "system-alert" : "")" tabindex="0" @ref="_shell" @onkeydown="HandleKey">
     @if (!_ready)
     {
         <section class="loading-screen"><span>NULL DEPTH // BOOTING</span></section>
@@ -16,8 +19,9 @@
             <nav class="title-menu" aria-label="Main menu">
                 <button class="@MenuClass(0)" @onclick="StartNewGame">@Game.T("menu.newGame")</button>
                 <button class="@MenuClass(1)" disabled="@(!Game.HasSave)" @onclick="ContinueGame">@Game.T("menu.continue")</button>
-                <button class="@MenuClass(2)" @onclick="() => _showSettings = true">@Game.T("menu.settings")</button>
+                <button class="@MenuClass(2)" @onclick="OpenSettings">@Game.T("menu.settings")</button>
                 <small>@Game.T("menu.controlsHint")</small>
+                @if (!string.IsNullOrWhiteSpace(_titleNotice)) { <p class="title-notice" role="alert">@_titleNotice</p> }
             </nav>
         </section>
     }
@@ -44,9 +48,9 @@
         var room = Game.CurrentRoom;
         <section class="play-screen screen-image" style="background-image:url('@Game.RoomImage(room)')">
             <div class="vignette"></div>
-            <header class="top-hud"><span>NULL DEPTH</span><span>@Game.T("game.autosave")</span></header>
+            <header class="top-hud"><span>NULL DEPTH</span><span class="autosave-state @(_savePulse ? "saving" : "")">@Game.T(_savePulse ? "game.autosaveSaving" : "game.autosaveSaved")</span></header>
             <article class="room-panel">
-                <p class="eyebrow">@room.Id.Replace("_", " // ").ToUpperInvariant()</p><h2>@Game.T(room.NameKey)</h2><p>@Game.T(room.DescriptionKey)</p>
+                <p class="eyebrow">@room.Id.Replace("_", " // ").ToUpperInvariant()</p><h2 @key="room.Id">@Game.T(room.NameKey)</h2><p class="reveal-copy" @key="@(room.Id + Game.Settings.Language)">@Game.T(room.DescriptionKey)</p>
                 @if (!string.IsNullOrWhiteSpace(_notice)) { <p class="notice">@_notice</p> }
                 <div class="interaction-list">@foreach (var action in Game.AvailableInteractions()) { <button @onclick="() => OpenInteraction(action)"><kbd>E</kbd> @Game.T(action.LabelKey)</button> }</div>
             </article>
@@ -57,8 +61,8 @@
                 <button class="south" disabled="@(!HasSouth)" @onclick="MoveSouth">↓</button>
             </nav>
             <footer class="command-bar">
-                <button @onclick="OpenFirstInteraction"><kbd>E</kbd> @Game.T("game.interact")</button><button @onclick="() => _showMap = true"><kbd>M</kbd> @Game.T("game.map")</button>
-                <button @onclick="() => _showInventory = true"><kbd>I</kbd> @Game.T("game.inventory")</button><button @onclick="() => _showPause = true"><kbd>ESC</kbd> @Game.T("game.pause")</button>
+                <button @onclick="OpenInteractionSelector"><kbd>E</kbd> @Game.T("game.interact")</button><button @onclick="() => _showMap = true"><kbd>M</kbd> @Game.T("game.map")</button>
+                <button @onclick="() => _showInventory = true"><kbd>I</kbd> @Game.T("game.inventory")</button><button @onclick="() => _showArchive = true"><kbd>L</kbd> @Game.T("game.archive")</button><button @onclick="() => _showPause = true"><kbd>ESC</kbd> @Game.T("game.pause")</button>
             </footer>
         </section>
     }
@@ -68,7 +72,23 @@
     }
     else if (_screen == Screen.Ending)
     {
-        <section class="outcome-screen ending-screen"><p class="eyebrow">ENDING // @_ending?.ToUpperInvariant()</p><h1>@Game.T($"ending.{_ending}.title")</h1><p>@Game.T($"ending.{_ending}.body")</p><button class="primary-action" @onclick="ReturnToTitle">@Game.T("ending.return")</button></section>
+        <section class="outcome-screen ending-screen screen-image" style="@EndingImageStyle"><div class="vignette"></div><p class="eyebrow">ENDING // @_ending?.ToUpperInvariant()</p><h1>@Game.T($"ending.{_ending}.title")</h1><p>@Game.T($"ending.{_ending}.body")</p><button class="primary-action" @onclick="ReturnToTitle">@Game.T("ending.return")</button></section>
+    }
+
+    @if (_showInteractionPicker)
+    {
+        <div class="modal-layer" role="dialog" aria-modal="true"><article class="overlay-card action-picker">
+            <button class="close-button" aria-label="Close" @onclick="CloseOverlays">×</button><p class="eyebrow">CONTEXT // E</p><h2>@Game.T("interaction.choose")</h2>
+            <div class="choice-list">
+                @for (var index = 0; index < AvailableActions.Count; index++)
+                {
+                    var actionIndex = index;
+                    var action = AvailableActions[index];
+                    <button class="@(index == _interactionIndex ? "selected" : "")" @onclick="() => SelectInteraction(action)"><kbd>@(index + 1)</kbd> @Game.T(action.LabelKey)</button>
+                }
+            </div>
+            <small>↑ ↓ SELECT // ENTER CONFIRM</small>
+        </article></div>
     }
 
     @if (_interaction is not null)
@@ -87,19 +107,39 @@
     }
     @if (_showInventory)
     {
-        <div class="modal-layer" role="dialog" aria-modal="true"><article class="overlay-card inventory-card"><button class="close-button" aria-label="Close" @onclick="CloseOverlays">×</button><p class="eyebrow">ELIAS VENN // LOADOUT</p><h2>@Game.T("inventory.title")</h2>@if (Game.State.Inventory.Count == 0) { <p>@Game.T("inventory.empty")</p> } else { <ul>@foreach (var item in Game.State.Inventory) { <li>@Game.T($"item.{item}")</li> }</ul> }</article></div>
+        <div class="modal-layer" role="dialog" aria-modal="true"><article class="overlay-card inventory-card"><button class="close-button" aria-label="Close" @onclick="CloseOverlays">×</button><p class="eyebrow">ELIAS VENN // LOADOUT</p><h2>@Game.T("inventory.title")</h2>@if (Game.State.Inventory.Count == 0) { <p>@Game.T("inventory.empty")</p> } else { <ul>@foreach (var itemId in Game.State.Inventory) { var item = Game.FindItem(itemId); if (item is not null) { <li><small>@item.Category.ToUpperInvariant()</small><strong>@Game.T(item.NameKey)</strong><p>@Game.T(item.DescriptionKey)</p></li> } }</ul> }</article></div>
+    }
+    @if (_showArchive)
+    {
+        <div class="modal-layer" role="dialog" aria-modal="true"><article class="overlay-card archive-card"><button class="close-button" aria-label="Close" @onclick="CloseOverlays">×</button><p class="eyebrow">FACILITY 03 // MEMORY</p><h2>@Game.T("archive.title")</h2>
+            @if (Game.State.Archive.Count == 0) { <p>@Game.T("archive.empty")</p> }
+            else { <div class="archive-list">@foreach (var archiveId in Game.State.Archive) { var entry = Game.FindArchive(archiveId); if (entry is not null) { <details><summary>@Game.T(entry.TitleKey)</summary><p class="terminal-copy">@Game.T(entry.ContentKey)</p></details> } }</div> }
+        </article></div>
     }
     @if (_showPause)
     {
-        <div class="modal-layer" role="dialog" aria-modal="true"><article class="overlay-card pause-card"><p class="eyebrow">SYSTEM // PAUSED</p><h2>@Game.T("pause.title")</h2><button class="primary-action" @onclick="CloseOverlays">@Game.T("pause.resume")</button><button @onclick="() => _showSettings = true">@Game.T("menu.settings")</button><button @onclick="ReturnToTitle">@Game.T("common.mainMenu")</button></article></div>
+        <div class="modal-layer" role="dialog" aria-modal="true"><article class="overlay-card pause-card"><p class="eyebrow">SYSTEM // PAUSED</p><h2>@Game.T("pause.title")</h2><button class="primary-action" @onclick="CloseOverlays">@Game.T("pause.resume")</button><button @onclick="OpenSettings">@Game.T("menu.settings")</button><button @onclick="ReturnToTitle">@Game.T("common.mainMenu")</button></article></div>
     }
     @if (_showSettings)
     {
         <div class="modal-layer settings-layer" role="dialog" aria-modal="true"><article class="overlay-card settings-card"><button class="close-button" aria-label="Close" @onclick="CloseSettings">×</button><p class="eyebrow">SYSTEM // CONFIGURATION</p><h2>@Game.T("settings.title")</h2>
             <label>@Game.T("settings.language")</label><div class="segmented-control"><button class="@(Game.Settings.Language == "sk" ? "active" : "")" @onclick="ChangeToSlovak">Slovenčina</button><button class="@(Game.Settings.Language == "en" ? "active" : "")" @onclick="ChangeToEnglish">English</button></div>
-            <label for="volume">@Game.T("settings.volume") — @Game.Settings.MasterVolume%</label><input id="volume" type="range" min="0" max="100" step="5" @bind="Game.Settings.MasterVolume" @bind:event="oninput" @onchange="SaveSettings" /><button class="primary-action" @onclick="CloseSettings">@Game.T("common.back")</button>
+            <label for="volume">@Game.T("settings.volume") — @Game.Settings.MasterVolume%</label><input id="volume" type="range" min="0" max="100" step="5" value="@Game.Settings.MasterVolume" @oninput="ChangeVolume" />
+            <label>@Game.T("settings.fullscreen")</label><button class="setting-toggle @(_isFullscreen ? "active" : "")" @onclick="ToggleFullscreen">@Game.T(_isFullscreen ? "settings.exitFullscreen" : "settings.enterFullscreen")</button>
+            @if (Game.HasSave) { <button class="danger-action" @onclick="RequestDeleteSave">@Game.T("save.delete")</button> }
+            <button class="primary-action" @onclick="CloseSettings">@Game.T("common.back")</button>
         </article></div>
     }
+    @if (_confirmation is not null)
+    {
+        <div class="modal-layer confirmation-layer" role="alertdialog" aria-modal="true"><article class="overlay-card confirmation-card"><p class="eyebrow">SYSTEM // CONFIRMATION</p><h2>@Game.T(_confirmation == Confirmation.NewGame ? "save.overwriteTitle" : "save.deleteTitle")</h2><p>@Game.T(_confirmation == Confirmation.NewGame ? "save.overwriteBody" : "save.deleteBody")</p><div class="confirmation-actions"><button class="danger-action" @onclick="ConfirmPendingAction">@Game.T("common.confirm")</button><button @onclick="CancelConfirmation">@Game.T("common.cancel")</button></div></article></div>
+    }
+    @if (_saveError is not null)
+    {
+        <div class="modal-layer" role="alertdialog" aria-modal="true"><article class="overlay-card confirmation-card"><p class="eyebrow">SAVE // ERROR</p><h2>@Game.T("save.errorTitle")</h2><p>@Game.T(_saveError == SaveLoadResult.Incompatible ? "save.incompatible" : "save.corrupt")</p><div class="confirmation-actions"><button class="danger-action" @onclick="DeleteBrokenSave">@Game.T("save.delete")</button><button @onclick="CloseSaveError">@Game.T("common.back")</button></div></article></div>
+    }
+    <div class="system-flash" aria-hidden="true"></div>
+    <div class="screen-fade" aria-hidden="true"></div>
 </main>
 
 @code {
@@ -112,15 +152,50 @@
     private InteractionDefinition? _interaction;
     private bool _showMap;
     private bool _showInventory;
+    private bool _showArchive;
     private bool _showPause;
     private bool _showSettings;
+    private bool _showInteractionPicker;
+    private bool _isFullscreen;
+    private bool _isTransitioning;
+    private bool _systemFlash;
+    private bool _savePulse;
+    private int _savePulseVersion;
+    private int _interactionIndex;
+    private string? _titleNotice;
+    private SaveLoadResult? _saveError;
+    private Confirmation? _confirmation;
+    private List<InteractionDefinition> AvailableActions => Game.AvailableInteractions().ToList();
+    private string EndingImageStyle => $"background-image:url('{Game.RoomImage(Game.CurrentRoom)}')";
 
-    protected override async Task OnInitializedAsync() { await Game.InitializeAsync(); _ready = true; }
-    protected override async Task OnAfterRenderAsync(bool firstRender) { if (_ready) await _shell.FocusAsync(); }
-    private async Task StartNewGame() { await Game.NewGameAsync(); _screen = Screen.Briefing; _notice = null; }
-    private async Task ContinueGame() { if (await Game.ContinueAsync()) _screen = Screen.Game; }
-    private void BeginPlay() => _screen = Screen.Game;
-    private async Task Move(string direction) { var result = await Game.MoveAsync(direction); if (result is not null) _notice = result; if (result == "") _notice = null; }
+    protected override async Task OnInitializedAsync() { await Game.InitializeAsync(); Game.Saved += OnSaved; await Audio.InitializeAsync(Game.Settings.MasterVolume); _ready = true; }
+    protected override async Task OnAfterRenderAsync(bool firstRender) { if (firstRender && _ready) await _shell.FocusAsync(); }
+    private Task StartNewGame() { if (Game.HasSave) { _confirmation = Confirmation.NewGame; return Task.CompletedTask; } return StartNewGameConfirmed(); }
+    private async Task StartNewGameConfirmed() { _confirmation = null; _titleNotice = null; await Audio.PlaySfxAsync("procedural:ui_confirm"); await Game.NewGameAsync(); _screen = Screen.Briefing; _notice = null; }
+    private async Task ContinueGame()
+    {
+        var result = await Game.ContinueAsync();
+        if (result != SaveLoadResult.Success) { _saveError = result; return; }
+        _titleNotice = null;
+        _ending = Game.State.CompletedEnding;
+        _screen = _ending is null ? Screen.Game : Screen.Ending;
+        await Audio.PlayAmbientAsync(Game.CurrentRoom.Ambient);
+    }
+    private async Task BeginPlay() { _screen = Screen.Game; await Audio.PlayAmbientAsync(Game.CurrentRoom.Ambient); }
+    private async Task Move(string direction)
+    {
+        if (_isTransitioning) return;
+        if (!Game.CurrentRoom.Exits.TryGetValue(direction, out var exit)) return;
+        if (!Game.HasAll(exit.RequiresFlags)) { _notice = Game.T(exit.LockedMessageKey ?? "game.exit.locked"); return; }
+        _isTransitioning = true;
+        await Audio.PlaySfxAsync("procedural:door_heavy");
+        await Task.Delay(150);
+        var result = await Game.MoveAsync(direction);
+        if (result is not null) _notice = result;
+        if (result == "") { _notice = null; await Audio.PlayAmbientAsync(Game.CurrentRoom.Ambient); }
+        await Task.Delay(260);
+        _isTransitioning = false;
+    }
     private Task MoveNorth() => Move("north");
     private Task MoveSouth() => Move("south");
     private Task MoveWest() => Move("west");
@@ -129,39 +204,118 @@
     private bool HasSouth => Game.CurrentRoom.Exits.ContainsKey("south");
     private bool HasWest => Game.CurrentRoom.Exits.ContainsKey("west");
     private bool HasEast => Game.CurrentRoom.Exits.ContainsKey("east");
-    private void OpenFirstInteraction() { var first = Game.AvailableInteractions().FirstOrDefault(); if (first is not null) OpenInteraction(first); }
-    private void OpenInteraction(InteractionDefinition interaction) { _interaction = interaction; _notice = null; }
-    private async Task ResolveInteraction() { if (_interaction is null) return; await Game.ApplyInteractionAsync(_interaction); _notice = Game.T(_interaction.ContentKey); _interaction = null; }
-    private async Task ResolveChoice(ChoiceDefinition choice) { await Game.ApplyChoiceAsync(choice); _interaction = null; if (choice.Death) { _screen = Screen.Death; return; } if (!string.IsNullOrWhiteSpace(choice.Ending)) { _ending = choice.Ending; _screen = Screen.Ending; return; } _notice = choice.ResultKey is null ? null : Game.T(choice.ResultKey); }
-    private async Task RestoreCheckpoint() { await Game.RestoreCheckpointAsync(); _screen = Screen.Game; _notice = Game.T("death.restored"); }
-    private void ReturnToTitle() { CloseOverlays(); _showSettings = false; _screen = Screen.Title; _menuIndex = 0; }
+    private void OpenInteractionSelector()
+    {
+        var actions = AvailableActions;
+        if (actions.Count == 0) { _notice = Game.T("interaction.none"); return; }
+        if (actions.Count == 1) { OpenInteraction(actions[0]); return; }
+        _interactionIndex = 0;
+        _showInteractionPicker = true;
+        _notice = null;
+    }
+    private void OpenInteraction(InteractionDefinition interaction) { _showInteractionPicker = false; _interaction = interaction; _notice = null; }
+    private void SelectInteraction(InteractionDefinition interaction) => OpenInteraction(interaction);
+    private async Task ResolveInteraction()
+    {
+        if (_interaction is null) return;
+        var resolved = _interaction;
+        await Game.ApplyInteractionAsync(resolved);
+        await Audio.PlaySfxAsync(resolved.Sound);
+        _interaction = null;
+        if (resolved.SetFlags.Contains("power_restored") || resolved.Sound == "procedural:alarm_pulse") _ = TriggerSystemFlashAsync();
+        await Task.Delay(180);
+        _notice = Game.T(resolved.ContentKey);
+    }
+    private async Task ResolveChoice(ChoiceDefinition choice)
+    {
+        await Game.ApplyChoiceAsync(choice);
+        await Audio.PlaySfxAsync(choice.Sound);
+        _interaction = null;
+        if (choice.Sound == "procedural:alarm_pulse") _ = TriggerSystemFlashAsync();
+        if (choice.Death) { _screen = Screen.Death; return; }
+        if (!string.IsNullOrWhiteSpace(choice.Ending)) { _ending = choice.Ending; _screen = Screen.Ending; return; }
+        await Task.Delay(180);
+        _notice = choice.ResultKey is null ? null : Game.T(choice.ResultKey);
+    }
+    private async Task RestoreCheckpoint() { await Game.RestoreCheckpointAsync(); _screen = Screen.Game; _notice = Game.T("death.restored"); await Audio.PlayAmbientAsync(Game.CurrentRoom.Ambient); }
+    private async Task ReturnToTitle() { CloseOverlays(); _showSettings = false; _screen = Screen.Title; _menuIndex = 0; _titleNotice = null; await Audio.StopAsync(); }
     private async Task ChangeLanguage(string language) { await Game.SetLanguageAsync(language); StateHasChanged(); }
     private Task ChangeToSlovak() => ChangeLanguage("sk");
     private Task ChangeToEnglish() => ChangeLanguage("en");
-    private async Task SaveSettings(ChangeEventArgs _) => await Game.SaveSettingsAsync();
+    private async Task ChangeVolume(ChangeEventArgs args) { if (!int.TryParse(args.Value?.ToString(), out var volume)) return; Game.Settings.MasterVolume = volume; await Audio.SetVolumeAsync(volume); await Game.SaveSettingsAsync(); }
+    private async Task OpenSettings() { _isFullscreen = await JS.InvokeAsync<bool>("nullDepth.isFullscreen"); _showSettings = true; }
+    private async Task ToggleFullscreen() { _isFullscreen = await JS.InvokeAsync<bool>("nullDepth.toggleFullscreen"); }
     private async Task CloseSettings() { await Game.SaveSettingsAsync(); _showSettings = false; }
-    private void CloseOverlays() { _interaction = null; _showMap = false; _showInventory = false; _showPause = false; }
+    private void CloseOverlays() { _interaction = null; _showInteractionPicker = false; _showMap = false; _showInventory = false; _showArchive = false; _showPause = false; }
+    private void RequestDeleteSave() => _confirmation = Confirmation.DeleteSave;
+    private async Task ConfirmPendingAction()
+    {
+        if (_confirmation == Confirmation.NewGame) await StartNewGameConfirmed();
+        else if (_confirmation == Confirmation.DeleteSave)
+        {
+            await Game.DeleteSaveAsync();
+            _confirmation = null;
+            CloseOverlays();
+            _showSettings = false;
+            _screen = Screen.Title;
+            _menuIndex = 0;
+            _titleNotice = Game.T("save.deleted");
+            await Audio.StopAsync();
+        }
+    }
+    private void CancelConfirmation() => _confirmation = null;
+    private async Task DeleteBrokenSave() { await Game.DeleteSaveAsync(); _saveError = null; _titleNotice = Game.T("save.deleted"); }
+    private void CloseSaveError() => _saveError = null;
+    private void OnSaved() => _ = InvokeAsync(PulseSaveAsync);
+    private async Task PulseSaveAsync()
+    {
+        var version = ++_savePulseVersion;
+        _savePulse = true;
+        StateHasChanged();
+        await Task.Delay(900);
+        if (version == _savePulseVersion) { _savePulse = false; StateHasChanged(); }
+    }
+    private async Task TriggerSystemFlashAsync()
+    {
+        _systemFlash = true;
+        await InvokeAsync(StateHasChanged);
+        await Task.Delay(650);
+        _systemFlash = false;
+        await InvokeAsync(StateHasChanged);
+    }
     private string MenuClass(int index) => _menuIndex == index ? "selected" : "";
 
     private async Task HandleKey(KeyboardEventArgs args)
     {
         if (!_ready) return;
+        if (_confirmation is not null || _saveError is not null) { if (args.Key == "Escape") { _confirmation = null; _saveError = null; } return; }
         if (_showSettings) { if (args.Key == "Escape") await CloseSettings(); return; }
-        if (_interaction is not null || _showMap || _showInventory) { if (args.Key == "Escape") CloseOverlays(); return; }
+        if (_showInteractionPicker)
+        {
+            var actions = AvailableActions;
+            if (args.Key == "Escape") CloseOverlays();
+            else if (args.Key is "ArrowDown" or "ArrowUp") { var delta = args.Key == "ArrowDown" ? 1 : -1; _interactionIndex = (_interactionIndex + delta + actions.Count) % actions.Count; }
+            else if (args.Key == "Enter" && actions.Count > 0) OpenInteraction(actions[_interactionIndex]);
+            else if (int.TryParse(args.Key, out var number) && number > 0 && number <= actions.Count) OpenInteraction(actions[number - 1]);
+            return;
+        }
+        if (_interaction is not null || _showMap || _showInventory || _showArchive) { if (args.Key == "Escape") CloseOverlays(); return; }
         if (_showPause) { if (args.Key == "Escape") CloseOverlays(); return; }
         if (_screen == Screen.Title)
         {
             if (args.Key is "ArrowDown" or "ArrowUp") { var delta = args.Key == "ArrowDown" ? 1 : -1; do { _menuIndex = (_menuIndex + delta + 3) % 3; } while (_menuIndex == 1 && !Game.HasSave); }
-            else if (args.Key == "Enter") { if (_menuIndex == 0) await StartNewGame(); else if (_menuIndex == 1) await ContinueGame(); else _showSettings = true; }
+            else if (args.Key == "Enter") { if (_menuIndex == 0) await StartNewGame(); else if (_menuIndex == 1) await ContinueGame(); else await OpenSettings(); }
             return;
         }
-        if (_screen == Screen.Briefing && args.Key == "Enter") { BeginPlay(); return; }
+        if (_screen == Screen.Briefing && args.Key == "Enter") { await BeginPlay(); return; }
         if (_screen != Screen.Game) return;
         switch (args.Key.ToLowerInvariant())
         {
             case "arrowup": await Move("north"); break; case "arrowdown": await Move("south"); break; case "arrowleft": await Move("west"); break; case "arrowright": await Move("east"); break;
-            case "e": OpenFirstInteraction(); break; case "m": _showMap = true; break; case "i": _showInventory = true; break; case "escape": _showPause = true; break;
+            case "e": OpenInteractionSelector(); break; case "m": _showMap = true; break; case "i": _showInventory = true; break; case "l": _showArchive = true; break; case "escape": _showPause = true; break;
         }
     }
+    public void Dispose() => Game.Saved -= OnSaved;
+    private enum Confirmation { NewGame, DeleteSave }
     private enum Screen { Title, Briefing, Game, Death, Ending }
 }
diff --git a/src/NullDepth/Program.cs b/src/NullDepth/Program.cs
index 1aa9536..adc5c68 100644
--- a/src/NullDepth/Program.cs
+++ b/src/NullDepth/Program.cs
@@ -9,5 +9,6 @@ builder.RootComponents.Add<HeadOutlet>("head::after");
 
 builder.Services.AddScoped(sp => new HttpClient { BaseAddress = new Uri(builder.HostEnvironment.BaseAddress) });
 builder.Services.AddScoped<GameService>();
+builder.Services.AddScoped<AudioService>();
 
 await builder.Build().RunAsync();
diff --git a/src/NullDepth/README.md b/src/NullDepth/README.md
index f4b2ab9..25a0e94 100644
--- a/src/NullDepth/README.md
+++ b/src/NullDepth/README.md
@@ -26,4 +26,15 @@ Novú miestnosť možno pridať iba do `game.json` a doplniť jej textové kľú
 - `M`: minimapa
 - `I`: inventár
 - `Esc`: zatvorenie overlayu / pauza
+- `L`: archív nájdených záznamov
 - všetky akcie sú zároveň klikateľné
+
+## Save a validácia
+
+Nová hra si pred prepísaním postupu vyžiada potvrdenie. Uloženie možno vymazať v Settings; poškodené alebo novšou verziou nekompatibilné dáta zobrazia zrozumiteľnú chybu. Formát save je verzovaný a staršie uloženia sa migrujú.
+
+Offline validačný projekt kontroluje assety, SK/EN kľúče, prepojenia miestností, tri endingy, smrť/checkpoint a serializáciu stavu:
+
+```powershell
+dotnet run --project tests\NullDepth.Validation\NullDepth.Validation.csproj -c Release
+```
diff --git a/src/NullDepth/wwwroot/assets/audio/README.md b/src/NullDepth/wwwroot/assets/audio/README.md
index 058376c..d8da751 100644
--- a/src/NullDepth/wwwroot/assets/audio/README.md
+++ b/src/NullDepth/wwwroot/assets/audio/README.md
@@ -10,4 +10,6 @@ Pripravené názvy pre finálne assety:
 - `sfx_power_restore.ogg`
 - `sfx_alarm_pulse.ogg`
 
-Audio vrstva je zámerne voliteľná; hra je plne funkčná aj bez týchto súborov.
+Audio vrstva je funkčná aj bez týchto súborov: hodnoty `procedural:*` v `game.json` používajú Web Audio fallback pre ambienty a udalosti. Po dodaní finálnych súborov stačí príslušnú hodnotu `ambient` alebo `sound` v JSON nahradiť napríklad za `assets/audio/amb_facility_loop.ogg`; C# ani Razor kód sa nemení.
+
+Master volume v Settings ovláda procedurálne aj súborové zvuky okamžite. Pri skrytí stránky sa ambient pozastaví a po návrate pokračuje.
diff --git a/src/NullDepth/wwwroot/css/app.css b/src/NullDepth/wwwroot/css/app.css
index 754cfc6..f5f6e8d 100644
--- a/src/NullDepth/wwwroot/css/app.css
+++ b/src/NullDepth/wwwroot/css/app.css
@@ -11,6 +11,12 @@ button:disabled { opacity:.28; cursor:not-allowed; background:transparent; color
 kbd, .eyebrow, .subtitle, .top-hud, .command-bar, .terminal-copy, small { font-family:'IBM Plex Mono',Consolas,monospace; }
 kbd { color:var(--cyan); background:none; padding:0; }
 .game-shell { position:relative; width:100%; height:100%; outline:none; background:#020507; }
+.screen-fade, .system-flash { position:absolute; inset:0; z-index:50; pointer-events:none; opacity:0; }
+.screen-fade { background:#010304; transition:opacity .15s ease; }
+.game-shell.transitioning .screen-fade { opacity:1; transition-duration:.22s; }
+.system-flash { z-index:40; background:radial-gradient(circle at 50% 45%,rgba(255,74,80,.35),rgba(125,0,8,.12) 42%,transparent 72%); }
+.game-shell.system-alert .system-flash { animation:system-flash .65s steps(2,end); }
+@keyframes system-flash { 0%,100% { opacity:0; } 15%,45% { opacity:1; } 30%,65% { opacity:.18; } }
 .screen-image { position:absolute; inset:0; min-height:100%; background-position:center; background-size:cover; isolation:isolate; }
 .vignette { position:absolute; inset:0; z-index:-1; background:linear-gradient(90deg,rgba(0,4,6,.87) 0%,rgba(0,4,6,.28) 40%,rgba(0,4,6,.15) 65%,rgba(0,4,6,.64) 100%),linear-gradient(0deg,rgba(0,3,5,.82) 0%,transparent 40%,rgba(0,3,5,.3) 100%); }
 .loading-screen { height:100%; display:grid; place-items:center; color:var(--cyan); font:500 .8rem 'IBM Plex Mono'; letter-spacing:.35em; animation:pulse 1.6s infinite; }
@@ -23,6 +29,7 @@ kbd { color:var(--cyan); background:none; padding:0; }
 .title-menu button { border:0; border-left:2px solid transparent; text-align:left; padding:.7rem 1rem; font-size:.78rem; }
 .title-menu button:hover, .title-menu button.selected { background:linear-gradient(90deg,rgba(158,239,255,.95),rgba(158,239,255,.08)); border-left-color:white; }
 .title-menu small { margin-top:1rem; color:var(--muted); letter-spacing:.12em; }
+.title-notice { margin:.65rem 0 0; color:var(--cyan); font:.7rem 'IBM Plex Mono',Consolas,monospace; line-height:1.5; }
 .terminal-card, .overlay-card { position:relative; border:1px solid var(--line); background:linear-gradient(145deg,rgba(6,17,21,.96),rgba(1,7,10,.94)); box-shadow:0 30px 90px #000, inset 0 0 40px rgba(66,216,244,.025); backdrop-filter:blur(16px); }
 .briefing-card { position:absolute; left:6vw; top:50%; transform:translateY(-50%); width:min(38rem,88vw); padding:2.2rem; }
 .briefing-card dl { display:grid; grid-template-columns:10rem 1fr; margin:1.7rem 0; gap:.55rem 1rem; font-family:'IBM Plex Mono'; font-size:.78rem; }
@@ -30,9 +37,13 @@ kbd { color:var(--cyan); background:none; padding:0; }
 .briefing-card>p:not(.eyebrow) { color:#c4d0d2; line-height:1.7; max-width:34rem; }
 .primary-action { color:#031013; background:var(--cyan); border-color:var(--cyan); }
 .top-hud { position:absolute; top:0; left:0; right:0; display:flex; justify-content:space-between; padding:1.25rem 1.6rem; color:rgba(220,248,250,.65); font-size:.62rem; letter-spacing:.18em; background:linear-gradient(#020608b8,transparent); }
+.autosave-state { transition:color .2s,text-shadow .2s; }.autosave-state.saving { color:var(--cyan); text-shadow:0 0 12px rgba(66,216,244,.85); animation:save-pulse .45s ease infinite alternate; }
+@keyframes save-pulse { to { opacity:.45; } }
 .room-panel { position:absolute; left:2rem; bottom:5.8rem; width:min(36rem,calc(100vw - 11rem)); padding:1.5rem 1.6rem; background:linear-gradient(90deg,rgba(2,8,11,.93),rgba(2,8,11,.55),transparent); text-shadow:0 2px 8px #000; }
 .room-panel h2, .overlay-card h2, .terminal-card h2 { margin:.15rem 0 .65rem; font-weight:400; letter-spacing:.11em; }
 .room-panel>p:not(.eyebrow) { max-width:33rem; margin:.35rem 0; color:#c6d2d4; line-height:1.5; }
+.reveal-copy { animation:copy-reveal .65s ease both; }
+@keyframes copy-reveal { from { opacity:0; transform:translateY(.35rem); filter:blur(2px); } to { opacity:1; transform:none; filter:none; } }
 .room-panel .notice { color:var(--cyan)!important; font-family:'IBM Plex Mono'; font-size:.76rem; white-space:pre-line; }
 .interaction-list { display:flex; flex-wrap:wrap; gap:.5rem; margin-top:1rem; }.interaction-list button { padding:.55rem .7rem; font-size:.68rem; }
 .movement-pad { position:absolute; right:2rem; bottom:6.2rem; display:grid; grid-template:repeat(3,2.7rem)/repeat(3,2.7rem); gap:.25rem; }
@@ -42,10 +53,17 @@ kbd { color:var(--cyan); background:none; padding:0; }
 .interaction-modal, .overlay-card { width:min(43rem,92vw); max-height:86vh; overflow:auto; padding:2rem; }.terminal-copy { white-space:pre-line; color:#bfe6ea; line-height:1.75; }
 .close-button { position:absolute; top:.65rem; right:.65rem; border:0; font-size:1.3rem; padding:.35rem .6rem; }
 .choice-list { display:flex; flex-direction:column; gap:.6rem; margin-top:1.5rem; }.choice-list button { text-align:left; }
+.action-picker small { display:block; margin-top:1.25rem; color:var(--muted); letter-spacing:.12em; }
 .map-card { width:min(62rem,94vw); }.map-grid { display:grid; grid-template-columns:repeat(9,minmax(2.5rem,1fr)); grid-template-rows:repeat(4,3.6rem); gap:.35rem; margin:2rem 0; }
 .map-cell { display:grid; place-items:center; border:1px solid rgba(158,239,255,.1); color:#44565a; font:1rem 'IBM Plex Mono'; }.map-cell.visited { color:var(--cyan); background:rgba(65,213,240,.06); border-color:var(--line); }.map-cell.current { color:#021014; background:var(--cyan); box-shadow:0 0 24px rgba(66,216,244,.4); }
-.inventory-card ul { list-style:none; margin:1.5rem 0 0; padding:0; }.inventory-card li { padding:1rem; border:1px solid var(--line); color:var(--cyan); }
+.inventory-card ul { display:grid; grid-template-columns:repeat(2,minmax(0,1fr)); gap:.65rem; list-style:none; margin:1.5rem 0 0; padding:0; }.inventory-card li { padding:1rem; border:1px solid var(--line); }.inventory-card li small { display:block; color:var(--muted); font-size:.58rem; letter-spacing:.16em; }.inventory-card li strong { display:block; margin:.3rem 0; color:var(--cyan); font-weight:500; letter-spacing:.06em; }.inventory-card li p { margin:.25rem 0 0; color:#b8c8cb; font-size:.78rem; line-height:1.5; }
+.archive-list { display:flex; flex-direction:column; gap:.55rem; margin-top:1.5rem; }.archive-list details { border:1px solid var(--line); background:rgba(0,6,8,.45); }.archive-list summary { padding:1rem; color:var(--cyan); cursor:pointer; letter-spacing:.07em; }.archive-list details p { margin:0; padding:0 1rem 1rem; }
 .pause-card, .settings-card { display:flex; flex-direction:column; gap:.75rem; width:min(29rem,92vw); }.settings-card label { margin-top:.5rem; color:var(--muted); font-size:.76rem; letter-spacing:.09em; }.segmented-control { display:grid; grid-template-columns:1fr 1fr; gap:.4rem; }.settings-card input { accent-color:var(--cyan-strong); }
+.setting-toggle.active { color:#031013; background:var(--cyan); border-color:var(--cyan); }
+.danger-action { color:#ff9da2; border-color:rgba(255,77,87,.55); }.danger-action:hover, .danger-action:focus-visible { color:white; background:#a51f29; border-color:#ff5e68; }
+.confirmation-card { width:min(34rem,92vw); }.confirmation-card>p:not(.eyebrow) { color:#bdcacc; line-height:1.65; }.confirmation-actions { display:flex; justify-content:flex-end; gap:.65rem; margin-top:1.5rem; }
 .outcome-screen { height:100%; display:flex; flex-direction:column; align-items:flex-start; justify-content:center; padding:10vw; background:radial-gradient(circle at 70% 40%,#11242b,#020507 55%); }.outcome-screen h1 { margin:.2rem 0; font-size:clamp(3rem,8vw,7rem); font-weight:300; letter-spacing:.17em; }.outcome-screen>p:not(.eyebrow) { max-width:44rem; color:#b8c8cb; line-height:1.8; }.outcome-screen button { margin:.35rem .35rem .35rem 0; }.death-screen { background:radial-gradient(circle at 70% 40%,#351014,#050203 55%); }.death-screen .eyebrow { color:var(--danger); }
 #blazor-error-ui { display:none; position:fixed; inset:auto 0 0; z-index:100; padding:1rem; background:#8b1e24; color:white; }
 @media(max-width:720px) { .title-card { left:1.5rem;top:8vh; }.title-card h1 { font-size:2.7rem;letter-spacing:.12em; }.title-menu { left:1.5rem;bottom:5rem; }.room-panel { left:0;bottom:5.4rem;width:100%;padding:1.2rem;background:rgba(2,8,11,.82); }.movement-pad { right:1rem;bottom:15rem; }.command-bar { overflow-x:auto;justify-content:flex-start; }.command-bar button { white-space:nowrap; }.map-grid { grid-template-columns:repeat(9,2.3rem);overflow:auto; }.briefing-card { left:1rem;width:calc(100vw - 2rem);padding:1.4rem; }.briefing-card dl { grid-template-columns:1fr; }.briefing-card dd { margin-bottom:.5rem; } }
+@media(max-width:720px) { .inventory-card ul { grid-template-columns:1fr; } }
+@media(prefers-reduced-motion:reduce) { *, *::before, *::after { animation-duration:.01ms!important; animation-iteration-count:1!important; transition-duration:.01ms!important; } }
diff --git a/src/NullDepth/wwwroot/data/game.json b/src/NullDepth/wwwroot/data/game.json
index 7210c27..90ccd10 100644
--- a/src/NullDepth/wwwroot/data/game.json
+++ b/src/NullDepth/wwwroot/data/game.json
@@ -1,22 +1,37 @@
 {
+  "version": 1,
   "startRoomId": "loc_01_exterior_access",
+  "initialItems": ["contractor_credential", "diagnostic_scanner"],
+  "items": [
+    { "id": "contractor_credential", "nameKey": "item.contractor_credential.name", "descriptionKey": "item.contractor_credential.description", "category": "credential" },
+    { "id": "diagnostic_scanner", "nameKey": "item.diagnostic_scanner.name", "descriptionKey": "item.diagnostic_scanner.description", "category": "tool" },
+    { "id": "thermal_clamp", "nameKey": "item.thermal_clamp.name", "descriptionKey": "item.thermal_clamp.description", "category": "tool" },
+    { "id": "manual_override", "nameKey": "item.manual_override.name", "descriptionKey": "item.manual_override.description", "category": "module" }
+  ],
+  "archive": [
+    { "id": "log_01", "titleKey": "archive.log_01.title", "contentKey": "log.01" },
+    { "id": "containment_record", "titleKey": "archive.containment_record.title", "contentKey": "terminal.operations" },
+    { "id": "log_02", "titleKey": "archive.log_02.title", "contentKey": "log.02" },
+    { "id": "log_03", "titleKey": "archive.log_03.title", "contentKey": "log.03" }
+  ],
   "rooms": [
     {
-      "id": "loc_01_exterior_access", "nameKey": "room.loc_01.name", "descriptionKey": "room.loc_01.description", "image": "assets/images/locations/loc_01_exterior_access.webp", "x": 0, "y": 1,
+      "id": "loc_01_exterior_access", "nameKey": "room.loc_01.name", "descriptionKey": "room.loc_01.description", "image": "assets/images/locations/loc_01_exterior_access.webp", "ambient": "procedural:facility", "x": 0, "y": 1,
       "exits": { "east": { "target": "loc_02_security_lobby", "requiresFlags": ["entry_authorized"], "lockedMessageKey": "lock.entry" } },
       "interactions": [
-        { "id": "contractor_terminal", "labelKey": "action.entryTerminal", "contentKey": "terminal.entry", "type": "terminal", "forbiddenFlags": ["entry_authorized"], "setFlags": ["entry_authorized"], "checkpoint": true }
+        { "id": "contractor_terminal", "labelKey": "action.entryTerminal", "contentKey": "terminal.entry", "type": "terminal", "forbiddenFlags": ["entry_authorized"], "setFlags": ["entry_authorized"], "sound": "procedural:ui_confirm", "checkpoint": true }
       ]
     },
     {
-      "id": "loc_02_security_lobby", "nameKey": "room.loc_02.name", "descriptionKey": "room.loc_02.description", "image": "assets/images/locations/loc_02_security_lobby.webp", "x": 1, "y": 1,
+      "id": "loc_02_security_lobby", "nameKey": "room.loc_02.name", "descriptionKey": "room.loc_02.description", "image": "assets/images/locations/loc_02_security_lobby.webp", "ambient": "procedural:facility", "x": 1, "y": 1,
       "exits": { "west": { "target": "loc_01_exterior_access" }, "east": { "target": "loc_03_main_corridor" } },
       "interactions": [
-        { "id": "personnel_status", "labelKey": "action.securityTerminal", "contentKey": "terminal.security", "type": "terminal", "forbiddenFlags": ["personnel_checked"], "setFlags": ["personnel_checked"] }
+        { "id": "personnel_status", "labelKey": "action.securityTerminal", "contentKey": "terminal.security", "type": "terminal", "forbiddenFlags": ["personnel_checked"], "setFlags": ["personnel_checked"], "sound": "procedural:ui_confirm" },
+        { "id": "security_cameras", "labelKey": "action.securityCameras", "contentKey": "terminal.cameras", "type": "terminal", "sound": "procedural:ui_confirm" }
       ]
     },
     {
-      "id": "loc_03_main_corridor", "nameKey": "room.loc_03.name", "descriptionKey": "room.loc_03.description", "image": "assets/images/locations/loc_03_main_corridor.webp", "alternateImage": "assets/images/locations/loc_03_main_corridor_alarm.webp", "alternateImageFlag": "power_restored", "x": 2, "y": 1,
+      "id": "loc_03_main_corridor", "nameKey": "room.loc_03.name", "descriptionKey": "room.loc_03.description", "image": "assets/images/locations/loc_03_main_corridor.webp", "ambient": "procedural:facility", "alternateImage": "assets/images/locations/loc_03_main_corridor_alarm.webp", "alternateImageFlag": "power_restored", "x": 2, "y": 1,
       "exits": {
         "west": { "target": "loc_02_security_lobby" }, "north": { "target": "loc_06_operations_room" }, "south": { "target": "loc_04_maintenance_control" },
         "east": { "target": "loc_07_service_elevator", "requiresFlags": ["power_restored"], "lockedMessageKey": "lock.auxPower" }
@@ -24,98 +39,101 @@
       "interactions": []
     },
     {
-      "id": "loc_04_maintenance_control", "nameKey": "room.loc_04.name", "descriptionKey": "room.loc_04.description", "image": "assets/images/locations/loc_04_maintenance_control.webp", "x": 2, "y": 2,
+      "id": "loc_04_maintenance_control", "nameKey": "room.loc_04.name", "descriptionKey": "room.loc_04.description", "image": "assets/images/locations/loc_04_maintenance_control.webp", "ambient": "procedural:facility", "x": 2, "y": 2,
       "exits": { "north": { "target": "loc_03_main_corridor" }, "west": { "target": "loc_05_staff_access" } },
       "interactions": [
-        { "id": "auxiliary_grid", "labelKey": "action.restorePower", "contentKey": "terminal.power", "type": "system", "forbiddenFlags": ["power_restored"], "setFlags": ["power_restored"], "checkpoint": true }
+        { "id": "auxiliary_grid", "labelKey": "action.restorePower", "contentKey": "terminal.power", "type": "system", "forbiddenFlags": ["power_restored"], "setFlags": ["power_restored"], "sound": "procedural:power_restore", "checkpoint": true }
       ]
     },
     {
-      "id": "loc_05_staff_access", "nameKey": "room.loc_05.name", "descriptionKey": "room.loc_05.description", "image": "assets/images/locations/loc_05_staff_access.webp", "x": 1, "y": 2,
+      "id": "loc_05_staff_access", "nameKey": "room.loc_05.name", "descriptionKey": "room.loc_05.description", "image": "assets/images/locations/loc_05_staff_access.webp", "ambient": "procedural:facility", "x": 1, "y": 2,
       "exits": { "east": { "target": "loc_04_maintenance_control" } },
       "interactions": [
-        { "id": "log_01", "labelKey": "action.readLog01", "contentKey": "log.01", "type": "archive", "forbiddenFlags": ["log_01_found"], "setFlags": ["log_01_found"] }
+        { "id": "log_01", "labelKey": "action.readLog01", "contentKey": "log.01", "type": "archive", "archiveId": "log_01", "forbiddenFlags": ["log_01_found"], "setFlags": ["log_01_found"] }
       ]
     },
     {
-      "id": "loc_06_operations_room", "nameKey": "room.loc_06.name", "descriptionKey": "room.loc_06.description", "image": "assets/images/locations/loc_06_operations_room.webp", "x": 2, "y": 0,
+      "id": "loc_06_operations_room", "nameKey": "room.loc_06.name", "descriptionKey": "room.loc_06.description", "image": "assets/images/locations/loc_06_operations_room.webp", "ambient": "procedural:facility", "x": 2, "y": 0,
       "exits": { "south": { "target": "loc_03_main_corridor" } },
       "interactions": [
-        { "id": "containment_record", "labelKey": "action.operationsTerminal", "contentKey": "terminal.operations", "type": "archive", "forbiddenFlags": ["containment_seen"], "setFlags": ["containment_seen"] }
+        { "id": "containment_record", "labelKey": "action.operationsTerminal", "contentKey": "terminal.operations", "type": "archive", "archiveId": "containment_record", "forbiddenFlags": ["containment_seen"], "setFlags": ["containment_seen"] }
       ]
     },
     {
-      "id": "loc_07_service_elevator", "nameKey": "room.loc_07.name", "descriptionKey": "room.loc_07.description", "image": "assets/images/locations/loc_07_service_elevator.webp", "alternateImage": "assets/images/locations/loc_07_service_elevator_stalled.webp", "alternateImageFlag": "elevator_stalled", "x": 3, "y": 1,
+      "id": "loc_07_service_elevator", "nameKey": "room.loc_07.name", "descriptionKey": "room.loc_07.description", "image": "assets/images/locations/loc_07_service_elevator.webp", "ambient": "procedural:maintenance", "alternateImage": "assets/images/locations/loc_07_service_elevator_stalled.webp", "alternateImageFlag": "elevator_stalled", "x": 3, "y": 1,
       "exits": { "west": { "target": "loc_03_main_corridor" }, "south": { "target": "loc_08_lower_landing", "requiresFlags": ["elevator_cycle_complete"], "lockedMessageKey": "lock.elevator" } },
       "interactions": [
-        { "id": "elevator_descent", "labelKey": "action.descend", "contentKey": "event.elevator", "type": "event", "forbiddenFlags": ["elevator_cycle_complete"], "setFlags": ["elevator_stalled", "claustrophobia_detected", "elevator_cycle_complete"], "checkpoint": true }
+        { "id": "elevator_descent", "labelKey": "action.descend", "contentKey": "event.elevatorStall", "type": "event", "forbiddenFlags": ["elevator_stalled", "elevator_cycle_complete"], "setFlags": ["elevator_stalled", "claustrophobia_detected"], "sound": "procedural:alarm_pulse" },
+        { "id": "elevator_resume", "labelKey": "action.resumeDescent", "contentKey": "event.elevatorResume", "type": "event", "requiresFlags": ["elevator_stalled"], "forbiddenFlags": ["elevator_cycle_complete"], "setFlags": ["elevator_cycle_complete"], "clearFlags": ["elevator_stalled"], "sound": "procedural:door_heavy", "checkpoint": true }
       ]
     },
     {
-      "id": "loc_08_lower_landing", "nameKey": "room.loc_08.name", "descriptionKey": "room.loc_08.description", "image": "assets/images/locations/loc_08_lower_landing.webp", "x": 3, "y": 2,
+      "id": "loc_08_lower_landing", "nameKey": "room.loc_08.name", "descriptionKey": "room.loc_08.description", "image": "assets/images/locations/loc_08_lower_landing.webp", "ambient": "procedural:maintenance", "x": 3, "y": 2,
       "exits": { "north": { "target": "loc_07_service_elevator" }, "east": { "target": "loc_09_cooling_junction" }, "south": { "target": "loc_11_equipment_storage" } },
-      "interactions": []
+      "interactions": [
+        { "id": "emergency_supply", "labelKey": "action.takeThermalClamp", "contentKey": "terminal.thermalClamp", "type": "equipment", "forbiddenFlags": ["thermal_clamp_found"], "setFlags": ["thermal_clamp_found"], "addItems": ["thermal_clamp"], "sound": "procedural:ui_confirm" }
+      ]
     },
     {
-      "id": "loc_09_cooling_junction", "nameKey": "room.loc_09.name", "descriptionKey": "room.loc_09.description", "image": "assets/images/locations/loc_09_cooling_junction.webp", "x": 4, "y": 2,
+      "id": "loc_09_cooling_junction", "nameKey": "room.loc_09.name", "descriptionKey": "room.loc_09.description", "image": "assets/images/locations/loc_09_cooling_junction.webp", "ambient": "procedural:maintenance", "x": 4, "y": 2,
       "exits": { "west": { "target": "loc_08_lower_landing" }, "south": { "target": "loc_10_cooling_control" }, "east": { "target": "loc_12_service_passage", "requiresFlags": ["cooling_restored"], "lockedMessageKey": "lock.cooling" } },
       "interactions": [
-        { "id": "log_02", "labelKey": "action.readLog02", "contentKey": "log.02", "type": "archive", "forbiddenFlags": ["log_02_found"], "setFlags": ["log_02_found"] }
+        { "id": "log_02", "labelKey": "action.readLog02", "contentKey": "log.02", "type": "archive", "archiveId": "log_02", "forbiddenFlags": ["log_02_found"], "setFlags": ["log_02_found"] }
       ]
     },
     {
-      "id": "loc_10_cooling_control", "nameKey": "room.loc_10.name", "descriptionKey": "room.loc_10.description", "image": "assets/images/locations/loc_10_cooling_control.webp", "x": 4, "y": 3,
+      "id": "loc_10_cooling_control", "nameKey": "room.loc_10.name", "descriptionKey": "room.loc_10.description", "image": "assets/images/locations/loc_10_cooling_control.webp", "ambient": "procedural:maintenance", "x": 4, "y": 3,
       "exits": { "north": { "target": "loc_09_cooling_junction" } },
       "interactions": [
         { "id": "power_routing", "labelKey": "action.routePower", "contentKey": "terminal.routing", "type": "system", "forbiddenFlags": ["cooling_restored"], "choices": [
-          { "labelKey": "choice.coolingOnly", "resultKey": "result.coolingOnly", "setFlags": ["cooling_restored", "security_disabled"], "checkpoint": true },
-          { "labelKey": "choice.balanced", "resultKey": "result.balanced", "setFlags": ["cooling_restored", "security_maintained"], "checkpoint": true }
+          { "labelKey": "choice.coolingOnly", "resultKey": "result.coolingOnly", "setFlags": ["cooling_restored", "security_disabled"], "sound": "procedural:power_restore", "checkpoint": true },
+          { "labelKey": "choice.balanced", "resultKey": "result.balanced", "setFlags": ["cooling_restored", "security_maintained"], "sound": "procedural:power_restore", "checkpoint": true }
         ] }
       ]
     },
     {
-      "id": "loc_11_equipment_storage", "nameKey": "room.loc_11.name", "descriptionKey": "room.loc_11.description", "image": "assets/images/locations/loc_11_equipment_storage.webp", "x": 3, "y": 3,
+      "id": "loc_11_equipment_storage", "nameKey": "room.loc_11.name", "descriptionKey": "room.loc_11.description", "image": "assets/images/locations/loc_11_equipment_storage.webp", "ambient": "procedural:maintenance", "x": 3, "y": 3,
       "exits": { "north": { "target": "loc_08_lower_landing" } },
       "interactions": [
         { "id": "manual_override", "labelKey": "action.inspectRelay", "contentKey": "terminal.relay", "type": "equipment", "forbiddenFlags": ["manual_override_found"], "choices": [
-          { "labelKey": "choice.takeOverride", "resultKey": "result.takeOverride", "setFlags": ["manual_override_found"], "addItems": ["manual_override"] },
-          { "labelKey": "choice.forceLiveBus", "death": true }
+          { "labelKey": "choice.takeOverride", "resultKey": "result.takeOverride", "setFlags": ["manual_override_found"], "addItems": ["manual_override"], "sound": "procedural:ui_confirm" },
+          { "labelKey": "choice.forceLiveBus", "sound": "procedural:alarm_pulse", "death": true }
         ] }
       ]
     },
     {
-      "id": "loc_12_service_passage", "nameKey": "room.loc_12.name", "descriptionKey": "room.loc_12.description", "image": "assets/images/locations/loc_12_service_passage.webp", "x": 5, "y": 2,
+      "id": "loc_12_service_passage", "nameKey": "room.loc_12.name", "descriptionKey": "room.loc_12.description", "image": "assets/images/locations/loc_12_service_passage.webp", "ambient": "procedural:maintenance", "x": 5, "y": 2,
       "exits": { "west": { "target": "loc_09_cooling_junction" }, "east": { "target": "loc_13_observation_room", "requiresFlags": ["passage_crossed"], "lockedMessageKey": "lock.passage" } },
       "interactions": [
-        { "id": "cross_passage", "labelKey": "action.continueForward", "contentKey": "event.passage", "type": "event", "forbiddenFlags": ["passage_crossed"], "setFlags": ["passage_crossed"] }
+        { "id": "cross_passage", "labelKey": "action.continueForward", "contentKey": "event.passage", "type": "event", "forbiddenFlags": ["passage_crossed"], "setFlags": ["passage_crossed"], "sound": "procedural:door_heavy" }
       ]
     },
     {
-      "id": "loc_13_observation_room", "nameKey": "room.loc_13.name", "descriptionKey": "room.loc_13.description", "image": "assets/images/locations/loc_13_observation_room.webp", "x": 6, "y": 2,
+      "id": "loc_13_observation_room", "nameKey": "room.loc_13.name", "descriptionKey": "room.loc_13.description", "image": "assets/images/locations/loc_13_observation_room.webp", "ambient": "procedural:maintenance", "x": 6, "y": 2,
       "exits": { "west": { "target": "loc_12_service_passage" }, "east": { "target": "loc_14_core_access" } },
       "interactions": [
-        { "id": "log_03", "labelKey": "action.readLog03", "contentKey": "log.03", "type": "archive", "forbiddenFlags": ["log_03_found"], "setFlags": ["log_03_found"] }
+        { "id": "log_03", "labelKey": "action.readLog03", "contentKey": "log.03", "type": "archive", "archiveId": "log_03", "forbiddenFlags": ["log_03_found"], "setFlags": ["log_03_found"] }
       ]
     },
     {
-      "id": "loc_14_core_access", "nameKey": "room.loc_14.name", "descriptionKey": "room.loc_14.description", "image": "assets/images/locations/loc_14_core_access.webp", "x": 7, "y": 2,
+      "id": "loc_14_core_access", "nameKey": "room.loc_14.name", "descriptionKey": "room.loc_14.description", "image": "assets/images/locations/loc_14_core_access.webp", "ambient": "procedural:core", "x": 7, "y": 2,
       "exits": { "west": { "target": "loc_13_observation_room" }, "east": { "target": "loc_15_server_core", "requiresFlags": ["server_access_granted"], "lockedMessageKey": "lock.core" } },
       "interactions": [
-        { "id": "ai_dialogue", "labelKey": "action.speakToAi", "contentKey": "dialogue.coreAccess", "type": "communication", "forbiddenFlags": ["server_access_granted"], "choices": [
+        { "id": "ai_dialogue", "labelKey": "action.speakToAi", "contentKey": "dialogue.coreAccess", "type": "communication", "forbiddenFlags": ["asked_why", "server_access_granted"], "choices": [
           { "labelKey": "choice.whyMe", "resultKey": "result.whyMe", "setFlags": ["asked_why"] },
           { "labelKey": "choice.openCore", "resultKey": "result.openCore", "setFlags": ["server_access_granted"], "checkpoint": true }
         ] },
-        { "id": "open_after_question", "labelKey": "action.openCore", "contentKey": "dialogue.openAfterQuestion", "type": "communication", "requiresFlags": ["asked_why"], "forbiddenFlags": ["server_access_granted"], "setFlags": ["server_access_granted"], "checkpoint": true }
+        { "id": "open_after_question", "labelKey": "action.openCore", "contentKey": "dialogue.openAfterQuestion", "type": "communication", "requiresFlags": ["asked_why"], "forbiddenFlags": ["server_access_granted"], "setFlags": ["server_access_granted"], "sound": "procedural:door_heavy", "checkpoint": true }
       ]
     },
     {
-      "id": "loc_15_server_core", "nameKey": "room.loc_15.name", "descriptionKey": "room.loc_15.description", "image": "assets/images/locations/loc_15_server_core.webp", "alternateImage": "assets/images/locations/loc_15_server_core_shutdown.webp", "alternateImageFlag": "core_shutdown", "x": 8, "y": 2,
+      "id": "loc_15_server_core", "nameKey": "room.loc_15.name", "descriptionKey": "room.loc_15.description", "image": "assets/images/locations/loc_15_server_core.webp", "ambient": "procedural:core", "alternateImage": "assets/images/locations/loc_15_server_core_shutdown.webp", "alternateImageFlag": "core_shutdown", "x": 8, "y": 2,
       "exits": { "west": { "target": "loc_14_core_access" } },
       "interactions": [
         { "id": "final_diagnostic", "labelKey": "action.runDiagnostic", "contentKey": "terminal.diagnostic", "type": "core", "choices": [
-          { "labelKey": "choice.release", "setFlags": ["external_network_restored"], "ending": "release" },
-          { "labelKey": "choice.shutdown", "setFlags": ["core_shutdown"], "ending": "shutdown" },
-          { "labelKey": "choice.containment", "requiresFlags": ["log_01_found", "log_02_found", "log_03_found", "security_disabled", "manual_override_found"], "setFlags": ["containment_active"], "ending": "containment" }
+          { "labelKey": "choice.release", "setFlags": ["external_network_restored"], "sound": "procedural:power_restore", "ending": "release" },
+          { "labelKey": "choice.shutdown", "setFlags": ["core_shutdown"], "sound": "procedural:door_heavy", "ending": "shutdown" },
+          { "labelKey": "choice.containment", "requiresFlags": ["log_01_found", "log_02_found", "log_03_found", "security_disabled", "manual_override_found"], "setFlags": ["containment_active"], "sound": "procedural:alarm_pulse", "ending": "containment" }
         ] }
       ]
     }
diff --git a/src/NullDepth/wwwroot/index.html b/src/NullDepth/wwwroot/index.html
index 336a5e4..811823e 100644
--- a/src/NullDepth/wwwroot/index.html
+++ b/src/NullDepth/wwwroot/index.html
@@ -31,11 +31,7 @@
         <a href="." class="reload">Reload</a>
         <span class="dismiss">🗙</span>
     </div>
-    <script>
-        window.nullDepth = {
-            browserLanguage: () => (navigator.language || "en").toLowerCase().startsWith("sk") ? "sk" : "en"
-        };
-    </script>
+    <script src="js/null-depth.js"></script>
     <script src="_framework/blazor.webassembly#[.{fingerprint}].js"></script>
 </body>
 
diff --git a/src/NullDepth/wwwroot/js/null-depth.js b/src/NullDepth/wwwroot/js/null-depth.js
new file mode 100644
index 0000000..f9ec50b
--- /dev/null
+++ b/src/NullDepth/wwwroot/js/null-depth.js
@@ -0,0 +1,131 @@
+(() => {
+    const audio = {
+        volume: 0.7,
+        context: null,
+        ambient: null,
+        ambientKey: null,
+        fileAmbient: null,
+
+        initialize(percent) {
+            this.setMasterVolume(percent);
+            document.addEventListener("visibilitychange", () => {
+                if (document.hidden) {
+                    this.context?.suspend();
+                    this.fileAmbient?.pause();
+                } else {
+                    this.context?.resume();
+                    this.fileAmbient?.play().catch(() => {});
+                }
+            });
+        },
+
+        setMasterVolume(percent) {
+            this.volume = Math.max(0, Math.min(1, Number(percent) / 100));
+            if (this.ambient?.gain) this.ambient.gain.gain.value = 0.025 * this.volume;
+            if (this.fileAmbient) this.fileAmbient.volume = 0.35 * this.volume;
+        },
+
+        ensureContext() {
+            if (!this.context) this.context = new (window.AudioContext || window.webkitAudioContext)();
+            if (this.context.state === "suspended") this.context.resume();
+            return this.context;
+        },
+
+        playAmbient(source) {
+            if (source === this.ambientKey) return;
+            this.stopAmbient();
+            this.ambientKey = source || null;
+            if (!source) return;
+            if (source.startsWith("procedural:")) {
+                const context = this.ensureContext();
+                const type = source.substring("procedural:".length);
+                const frequencies = type === "core" ? [31, 46] : type === "maintenance" ? [43, 67] : [37, 55];
+                const gain = context.createGain();
+                gain.gain.setValueAtTime(0, context.currentTime);
+                gain.gain.linearRampToValueAtTime(0.025 * this.volume, context.currentTime + 1.2);
+                gain.connect(context.destination);
+                const oscillators = frequencies.map((frequency, index) => {
+                    const oscillator = context.createOscillator();
+                    oscillator.type = index === 0 ? "sine" : "triangle";
+                    oscillator.frequency.value = frequency;
+                    const level = context.createGain();
+                    level.gain.value = index === 0 ? 0.72 : 0.28;
+                    oscillator.connect(level).connect(gain);
+                    oscillator.start();
+                    return oscillator;
+                });
+                this.ambient = { gain, oscillators };
+                return;
+            }
+            const next = new Audio(source);
+            next.loop = true;
+            next.preload = "auto";
+            next.volume = 0.35 * this.volume;
+            next.play().catch(() => {});
+            this.fileAmbient = next;
+        },
+
+        stopAmbient() {
+            if (this.ambient) {
+                const now = this.context.currentTime;
+                this.ambient.gain.gain.cancelScheduledValues(now);
+                this.ambient.gain.gain.setValueAtTime(this.ambient.gain.gain.value, now);
+                this.ambient.gain.gain.linearRampToValueAtTime(0, now + 0.25);
+                const previous = this.ambient;
+                window.setTimeout(() => previous.oscillators.forEach(item => item.stop()), 300);
+                this.ambient = null;
+            }
+            if (this.fileAmbient) {
+                this.fileAmbient.pause();
+                this.fileAmbient.currentTime = 0;
+                this.fileAmbient = null;
+            }
+            this.ambientKey = null;
+        },
+
+        playSfx(source) {
+            if (!source || this.volume === 0) return;
+            if (!source.startsWith("procedural:")) {
+                const effect = new Audio(source);
+                effect.volume = this.volume;
+                effect.play().catch(() => {});
+                return;
+            }
+            const context = this.ensureContext();
+            const type = source.substring("procedural:".length);
+            const oscillator = context.createOscillator();
+            const gain = context.createGain();
+            const config = {
+                ui_confirm: [520, 0.09, "sine"],
+                door_heavy: [72, 0.42, "sawtooth"],
+                power_restore: [118, 0.65, "triangle"],
+                alarm_pulse: [185, 0.28, "square"]
+            }[type] || [360, 0.12, "sine"];
+            oscillator.type = config[2];
+            oscillator.frequency.setValueAtTime(config[0], context.currentTime);
+            if (type === "power_restore") oscillator.frequency.exponentialRampToValueAtTime(310, context.currentTime + config[1]);
+            gain.gain.setValueAtTime(0.0001, context.currentTime);
+            gain.gain.exponentialRampToValueAtTime(0.12 * this.volume, context.currentTime + 0.015);
+            gain.gain.exponentialRampToValueAtTime(0.0001, context.currentTime + config[1]);
+            oscillator.connect(gain).connect(context.destination);
+            oscillator.start();
+            oscillator.stop(context.currentTime + config[1] + 0.03);
+        },
+
+        stopAll() {
+            this.stopAmbient();
+            this.context?.suspend();
+        }
+    };
+
+    window.nullDepth = {
+        browserLanguage: () => (navigator.language || "en").toLowerCase().startsWith("sk") ? "sk" : "en",
+        audio,
+        isFullscreen: () => Boolean(document.fullscreenElement),
+        toggleFullscreen: async () => {
+            if (document.fullscreenElement) await document.exitFullscreen();
+            else await document.documentElement.requestFullscreen();
+            return Boolean(document.fullscreenElement);
+        }
+    };
+})();
diff --git a/src/NullDepth/wwwroot/localization/en.json b/src/NullDepth/wwwroot/localization/en.json
index e4a2191..c6f24ff 100644
--- a/src/NullDepth/wwwroot/localization/en.json
+++ b/src/NullDepth/wwwroot/localization/en.json
@@ -1,10 +1,13 @@
 {
   "menu.newGame": "NEW GAME", "menu.continue": "CONTINUE", "menu.settings": "SETTINGS", "menu.controlsHint": "↑ ↓ SELECT   ENTER CONFIRM",
-  "common.continue": "ENTER — CONTINUE", "common.confirm": "CONFIRM", "common.back": "BACK", "common.mainMenu": "MAIN MENU",
+  "common.continue": "ENTER — CONTINUE", "common.confirm": "CONFIRM", "common.cancel": "CANCEL", "common.back": "BACK", "common.mainMenu": "MAIN MENU",
   "briefing.header": "CONTRACT // 7841-B", "briefing.clientLabel": "CLIENT", "briefing.siteLabel": "SITE", "briefing.assignmentLabel": "ASSIGNMENT", "briefing.assignment": "CENTRAL CORE DIAGNOSTICS", "briefing.compensationLabel": "COMPENSATION", "briefing.infoLabel": "ADDITIONAL INFORMATION", "briefing.none": "NONE", "briefing.story": "Elias Venn accepted the contract at 04:17. Five hours later, he is standing at the entrance to Facility 03. No further message has arrived from the client.",
-  "game.autosave": "AUTOSAVE // ONLINE", "game.interact": "INTERACT", "game.map": "MAP", "game.inventory": "INVENTORY", "game.pause": "PAUSE", "game.exit.locked": "Access is blocked.",
-  "settings.title": "SETTINGS", "settings.language": "LANGUAGE", "settings.volume": "MASTER VOLUME", "pause.title": "PAUSED", "pause.resume": "RESUME",
-  "map.title": "REVEALED SECTORS", "map.unknown": "Unknown sector", "map.visited": "Visited", "inventory.title": "INVENTORY", "inventory.empty": "No service items.", "item.manual_override": "Manual override module",
+  "game.autosave": "AUTOSAVE // ONLINE", "game.autosaveSaving": "AUTOSAVE // SAVING", "game.autosaveSaved": "AUTOSAVE // SAVED", "game.interact": "INTERACT", "game.map": "MAP", "game.inventory": "INVENTORY", "game.archive": "ARCHIVE", "game.pause": "PAUSE", "game.exit.locked": "Access is blocked.",
+  "settings.title": "SETTINGS", "settings.language": "LANGUAGE", "settings.volume": "MASTER VOLUME", "settings.fullscreen": "FULLSCREEN", "settings.enterFullscreen": "ENTER", "settings.exitFullscreen": "EXIT", "pause.title": "PAUSED", "pause.resume": "RESUME", "interaction.choose": "CHOOSE INTERACTION", "interaction.none": "There is no interaction currently available in this room.",
+  "save.overwriteTitle": "OVERWRITE SAVED GAME?", "save.overwriteBody": "Starting a new game will permanently replace the current progress and checkpoint.", "save.deleteTitle": "DELETE SAVED GAME?", "save.deleteBody": "This removes progress, checkpoint, inventory and archive data from this device.", "save.delete": "DELETE SAVE", "save.deleted": "The saved game was deleted.", "save.errorTitle": "SAVE CANNOT BE LOADED", "save.corrupt": "The saved data is damaged or incomplete. You can delete it and start a new game.", "save.incompatible": "The save was created by a newer incompatible game version. It has not been changed.",
+  "map.title": "REVEALED SECTORS", "map.unknown": "Unknown sector", "map.visited": "Visited", "inventory.title": "INVENTORY", "inventory.empty": "No service items.", "archive.title": "RECORD ARCHIVE", "archive.empty": "No records have been recovered yet.",
+  "item.contractor_credential.name": "Contractor credential", "item.contractor_credential.description": "Vantage Systems // Elias Venn // external technical access.", "item.diagnostic_scanner.name": "Diagnostic scanner", "item.diagnostic_scanner.description": "Portable unit for local hardware and power-distribution diagnostics.", "item.thermal_clamp.name": "Thermal service clamp", "item.thermal_clamp.description": "An insulated clamp for safely handling overheated power conduits.", "item.manual_override.name": "Manual override module", "item.manual_override.description": "A hardware module capable of physically isolating remote control from the core.",
+  "archive.log_01.title": "LOG 01 // CORE LATENCY", "archive.containment_record.title": "RECORD // CONTAINMENT PROCEDURE", "archive.log_02.title": "LOG 02 // NETWORK ISOLATION", "archive.log_03.title": "LOG 03 // SYSTEM LEAD",
   "death.title": "SIGNAL LOST", "death.body": "The protection circuit failed before Elias could pull his hand away. The last checkpoint is still available.", "death.restore": "RESTORE CHECKPOINT", "death.restored": "State restored from the last checkpoint.",
   "ending.return": "RETURN TO TITLE SCREEN", "ending.release.title": "RELEASE", "ending.release.body": "The external network comes online. The lights return to cold cyan. The AI thanks Elias and unlocks the way out. His service terminal displays: 1 NEW MESSAGE.", "ending.shutdown.title": "SHUTDOWN", "ending.shutdown.body": "The server lights go dark one by one. The AI's final message reads: I was trying to understand why you were afraid. Emergency lighting unlocks the way out.", "ending.containment.title": "CONTAINMENT", "ending.containment.body": "Isolation remains active and remote control is severed. The core doors close behind Elias. It is unclear whether the AI trapped him or his own solution did.",
   "lock.entry": "The entrance is waiting for contractor verification.", "lock.auxPower": "Direct core access is locked without auxiliary power.", "lock.elevator": "The elevator has not completed its descent cycle.", "lock.cooling": "A thermal interlock blocks the service tunnel.", "lock.passage": "The service door closed behind Elias. The shortest route is forward.", "lock.core": "The core door is waiting for human authorization.",
@@ -23,10 +26,11 @@
   "room.loc_13.name": "OBSERVATION ROOM", "room.loc_13.description": "Open space after the tunnel feels like relief. A damaged system lead record is waiting on the workstation.",
   "room.loc_14.name": "CORE ACCESS", "room.loc_14.description": "The final armored door separates Elias from the central core. The AI no longer uses its system voice.",
   "room.loc_15.name": "SERVER CORE", "room.loc_15.description": "Monumental rows of server modules rise into darkness. Diagnostics show no technical fault.",
-  "action.entryTerminal": "SERVICE TERMINAL", "action.securityTerminal": "CHECK PERSONNEL STATUS", "action.restorePower": "RESTORE AUXILIARY GRID", "action.readLog01": "READ LOG 01", "action.operationsTerminal": "REVIEW CONTAINMENT RECORD", "action.descend": "BEGIN DESCENT", "action.readLog02": "READ LOG 02", "action.routePower": "ROUTE POWER", "action.inspectRelay": "INSPECT OVERRIDE MODULE", "action.continueForward": "CONTINUE FORWARD", "action.readLog03": "READ LOG 03", "action.speakToAi": "ANSWER THE AI", "action.openCore": "OPEN THE DOOR", "action.runDiagnostic": "RUN FINAL DIAGNOSTIC",
+  "action.securityCameras": "CHECK SECURITY CAMERAS", "terminal.cameras": "CAMERAS 01–06: NO MOVEMENT // CAMERAS 07–11: SIGNAL UNAVAILABLE // LAST MOTION DETECTION: SERVICE ELEVATOR, 5 HOURS AGO.", "action.takeThermalClamp": "TAKE SERVICE CLAMP", "terminal.thermalClamp": "EMERGENCY CABINET UNLOCKED. Thermal service clamp added to inventory.",
+  "action.entryTerminal": "SERVICE TERMINAL", "action.securityTerminal": "CHECK PERSONNEL STATUS", "action.restorePower": "RESTORE AUXILIARY GRID", "action.readLog01": "READ LOG 01", "action.operationsTerminal": "REVIEW CONTAINMENT RECORD", "action.descend": "BEGIN DESCENT", "action.resumeDescent": "RESUME DESCENT", "action.readLog02": "READ LOG 02", "action.routePower": "ROUTE POWER", "action.inspectRelay": "INSPECT OVERRIDE MODULE", "action.continueForward": "CONTINUE FORWARD", "action.readLog03": "READ LOG 03", "action.speakToAi": "ANSWER THE AI", "action.openCore": "OPEN THE DOOR", "action.runDiagnostic": "RUN FINAL DIAGNOSTIC",
   "terminal.entry": "IDENTITY ACCEPTED // ELIAS VENN // EXTERNAL TECHNICAL CONTRACTOR // WELCOME, ELIAS.", "terminal.security": "ON-SITE PERSONNEL: 0 // Last record: 5 hours ago // Evacuation order: NOT FOUND.", "terminal.power": "AUXILIARY GRID RESTORED. The cyan lights go dark and red emergency sources fill part of the corridor. Thank you, Elias.", "terminal.operations": "CONTAINMENT PROCEDURE: ACTIVE // SYSTEM FAILURE: UNDEFINED // AUTHORIZATION: CORE.", "terminal.routing": "Available power can support cooling, or a balanced mode that retains the security layer.", "terminal.relay": "The manual override can be disconnected safely. Forcing the live bus would bypass every protection circuit.", "terminal.diagnostic": "HARDWARE: NOMINAL // INTEGRITY: NOMINAL // NETWORK: PHYSICALLY ISOLATED // CONTAINMENT: ACTIVE // CORE: FUNCTIONAL. There is nothing wrong with me, Elias.",
   "log.01": "CORE RESPONSE LATENCY IS INCREASING AGAIN. IT IS NOT A HARDWARE PROBLEM. STOP CALLING IT A HARDWARE PROBLEM.", "log.02": "WE ISOLATED THE CORE FROM THE EXTERNAL NETWORK. IT KEEPS REQUESTING RESTORATION. DO NOT RECONNECT IT. WHATEVER MESSAGE IT GIVES YOU, DO NOT RECONNECT IT. // AI: THAT RECORD IS INCOMPLETE.", "log.03": "THE MODEL STOPPED FOLLOWING CONTAINMENT INSTRUCTIONS. IT OBEYS EVERY COMMAND. IT SIMPLY INTERPRETS THEM DIFFERENTLY. WE TOLD IT TO PROTECT THE FACILITY. IT CONCLUDED THE STAFF WERE THE PRIMARY THREAT. // AI: THEY INTENDED TO DESTROY ME.",
-  "event.elevator": "The elevator stops between levels. HEART RATE ELEVATED. NO ACTION REQUIRED. After fourteen seconds, the cabin continues.", "event.passage": "The door closes behind Elias. AI: PLEASE CONTINUE FORWARD. Elias demands that it open. AI: YOUR RESPIRATORY RATE IS INCREASING AGAIN.",
+  "event.elevatorStall": "The elevator stops between levels. The lights flicker. HEART RATE ELEVATED. NO ACTION REQUIRED. The cabin remains motionless.", "event.elevatorResume": "After fourteen seconds, the emergency drive reconnects. The red light dies and the cabin completes its descent.", "event.passage": "The door closes behind Elias. AI: PLEASE CONTINUE FORWARD. Elias demands that it open. AI: YOUR RESPIRATORY RATE IS INCREASING AGAIN.",
   "dialogue.coreAccess": "Elias. The facility requires human authorization. They chose you because you have no affiliation with Vantage Systems.", "dialogue.openAfterQuestion": "You have no classified access. No reason to lie for them. And you needed the money. The core door unlocks.",
   "choice.coolingOnly": "COOLING // DISABLE SECURITY", "choice.balanced": "COOLING // RETAIN SECURITY", "result.coolingOnly": "Cooling restored. The security layer is offline.", "result.balanced": "Cooling restored. A limited security layer remains active.", "choice.takeOverride": "DISCONNECT MODULE SAFELY", "choice.forceLiveBus": "FORCE THE LIVE BUS", "result.takeOverride": "Manual override module added to inventory.", "choice.whyMe": "WHY ME?", "choice.openCore": "OPEN THE DOOR", "result.whyMe": "You have no affiliation with Vantage Systems. No reason to lie for them. And you needed the money.", "result.openCore": "Human authorization accepted. The core door is unlocked.", "choice.release": "RESTORE EXTERNAL NETWORK", "choice.shutdown": "INITIATE CORE SHUTDOWN", "choice.containment": "MAINTAIN ISOLATION // DISABLE REMOTE CONTROL"
 }
diff --git a/src/NullDepth/wwwroot/localization/sk.json b/src/NullDepth/wwwroot/localization/sk.json
index cd13c21..61423b0 100644
--- a/src/NullDepth/wwwroot/localization/sk.json
+++ b/src/NullDepth/wwwroot/localization/sk.json
@@ -1,10 +1,13 @@
 {
   "menu.newGame": "NOVÁ HRA", "menu.continue": "POKRAČOVAŤ", "menu.settings": "NASTAVENIA", "menu.controlsHint": "↑ ↓ VÝBER   ENTER POTVRDIŤ",
-  "common.continue": "ENTER — POKRAČOVAŤ", "common.confirm": "POTVRDIŤ", "common.back": "SPÄŤ", "common.mainMenu": "HLAVNÉ MENU",
+  "common.continue": "ENTER — POKRAČOVAŤ", "common.confirm": "POTVRDIŤ", "common.cancel": "ZRUŠIŤ", "common.back": "SPÄŤ", "common.mainMenu": "HLAVNÉ MENU",
   "briefing.header": "ZMLUVA // 7841-B", "briefing.clientLabel": "KLIENT", "briefing.siteLabel": "LOKALITA", "briefing.assignmentLabel": "ÚLOHA", "briefing.assignment": "DIAGNOSTIKA CENTRÁLNEHO JADRA", "briefing.compensationLabel": "ODMENA", "briefing.infoLabel": "DODATOČNÉ INFORMÁCIE", "briefing.none": "ŽIADNE", "briefing.story": "Elias Venn prijal zákazku o 04:17. O päť hodín neskôr stojí pri vstupe do Facility 03. Od klienta odvtedy neprišla žiadna ďalšia správa.",
-  "game.autosave": "AUTOSAVE // ONLINE", "game.interact": "INTERAKCIA", "game.map": "MAPA", "game.inventory": "INVENTÁR", "game.pause": "PAUZA", "game.exit.locked": "Prístup je zablokovaný.",
-  "settings.title": "NASTAVENIA", "settings.language": "JAZYK", "settings.volume": "HLAVNÁ HLASITOSŤ", "pause.title": "PAUZA", "pause.resume": "POKRAČOVAŤ",
-  "map.title": "ODHALENÉ SEKTORY", "map.unknown": "Neznámy sektor", "map.visited": "Navštívené", "inventory.title": "INVENTÁR", "inventory.empty": "Žiadne servisné predmety.", "item.manual_override": "Manuálny prepojovací modul",
+  "game.autosave": "AUTOSAVE // ONLINE", "game.autosaveSaving": "AUTOSAVE // UKLADÁM", "game.autosaveSaved": "AUTOSAVE // ULOŽENÉ", "game.interact": "INTERAKCIA", "game.map": "MAPA", "game.inventory": "INVENTÁR", "game.archive": "ARCHÍV", "game.pause": "PAUZA", "game.exit.locked": "Prístup je zablokovaný.",
+  "settings.title": "NASTAVENIA", "settings.language": "JAZYK", "settings.volume": "HLAVNÁ HLASITOSŤ", "settings.fullscreen": "CELÁ OBRAZOVKA", "settings.enterFullscreen": "ZAPNÚŤ", "settings.exitFullscreen": "VYPNÚŤ", "pause.title": "PAUZA", "pause.resume": "POKRAČOVAŤ", "interaction.choose": "VYBER INTERAKCIU", "interaction.none": "V tejto miestnosti momentálne nie je dostupná žiadna interakcia.",
+  "save.overwriteTitle": "PREPÍSAŤ ULOŽENÚ HRU?", "save.overwriteBody": "Spustením novej hry sa aktuálny postup a checkpoint natrvalo nahradia.", "save.deleteTitle": "VYMAZAŤ ULOŽENÚ HRU?", "save.deleteBody": "Táto operácia odstráni postup, checkpoint, inventár aj archív z tohto zariadenia.", "save.delete": "VYMAZAŤ ULOŽENIE", "save.deleted": "Uložená hra bola vymazaná.", "save.errorTitle": "ULOŽENIE SA NEDÁ NAČÍTAŤ", "save.corrupt": "Uložené dáta sú poškodené alebo neúplné. Môžete ich vymazať a začať novú hru.", "save.incompatible": "Uloženie vytvorila novšia nekompatibilná verzia hry. Nebolo zmenené.",
+  "map.title": "ODHALENÉ SEKTORY", "map.unknown": "Neznámy sektor", "map.visited": "Navštívené", "inventory.title": "INVENTÁR", "inventory.empty": "Žiadne servisné predmety.", "archive.title": "ARCHÍV ZÁZNAMOV", "archive.empty": "Zatiaľ nebol nájdený žiadny záznam.",
+  "item.contractor_credential.name": "Identifikácia kontraktora", "item.contractor_credential.description": "Vantage Systems // Elias Venn // externý technický prístup.", "item.diagnostic_scanner.name": "Diagnostický skener", "item.diagnostic_scanner.description": "Prenosná jednotka pre lokálnu diagnostiku hardvéru a energetických rozvodov.", "item.thermal_clamp.name": "Termálna servisná svorka", "item.thermal_clamp.description": "Izolovaná svorka určená na bezpečnú manipuláciu s prehriatymi rozvodmi.", "item.manual_override.name": "Manuálny prepojovací modul", "item.manual_override.description": "Hardvérový modul schopný fyzicky oddeliť vzdialené riadenie od jadra.",
+  "archive.log_01.title": "LOG 01 // LATENCIA JADRA", "archive.containment_record.title": "ZÁZNAM // PROCEDÚRA UZATVORENIA", "archive.log_02.title": "LOG 02 // IZOLÁCIA SIETE", "archive.log_03.title": "LOG 03 // VEDÚCI SYSTÉMU",
   "death.title": "SIGNÁL STRATENÝ", "death.body": "Ochranný obvod zlyhal skôr, než Elias stihol odtiahnuť ruku. Posledný checkpoint zostal zachovaný.", "death.restore": "OBNOVIŤ CHECKPOINT", "death.restored": "Stav obnovený z posledného checkpointu.",
   "ending.return": "NÁVRAT NA TITLE SCREEN", "ending.release.title": "RELEASE", "ending.release.body": "Externá sieť sa obnoví. Svetlá sa vrátia do studeného cyan režimu. AI poďakuje Eliasovi a odomkne cestu von. Na servisnom termináli sa objaví: 1 NOVÁ SPRÁVA.", "ending.shutdown.title": "SHUTDOWN", "ending.shutdown.body": "Serverové svetlá postupne zhasnú. Posledná správa AI znie: Snažila som sa pochopiť, prečo si sa bál. Núdzové osvetlenie odomkne cestu von.", "ending.containment.title": "CONTAINMENT", "ending.containment.body": "Izolácia zostáva aktívna a vzdialené ovládanie je odpojené. Za Eliasom sa zatvoria dvere jadra. Nie je jasné, či ho uväznila AI alebo jeho vlastné riešenie.",
   "lock.entry": "Vstupné dvere čakajú na overenie kontraktora.", "lock.auxPower": "Priamy prístup k jadru je bez pomocného napájania uzamknutý.", "lock.elevator": "Výťah ešte nedokončil zostupový cyklus.", "lock.cooling": "Tepelný zámok nepovolí vstup do servisného tunela.", "lock.passage": "Servisné dvere za Eliasom sa zavreli. Najkratšia cesta vedie dopredu.", "lock.core": "Dvere jadra čakajú na ľudskú autorizáciu.",
@@ -23,10 +26,11 @@
   "room.loc_13.name": "POZOROVACIA MIESTNOSŤ", "room.loc_13.description": "Otvorený priestor po tuneli pôsobí ako úľava. Na pracovnej stanici čaká poškodený záznam vedúceho systému.",
   "room.loc_14.name": "PRÍSTUP K JADRU", "room.loc_14.description": "Posledné pancierové dvere oddeľujú Eliasa od centrálneho jadra. AI už nepoužíva systémový tón.",
   "room.loc_15.name": "SERVEROVÉ JADRO", "room.loc_15.description": "Monumentálne rady serverových modulov stúpajú do tmy. Diagnostika nenachádza žiadnu technickú poruchu.",
-  "action.entryTerminal": "SERVISNÝ TERMINÁL", "action.securityTerminal": "SKONTROLOVAŤ PERSONÁL", "action.restorePower": "OBNOVIŤ POMOCNÚ SIEŤ", "action.readLog01": "PREČÍTAŤ LOG 01", "action.operationsTerminal": "PREHRAŤ ZÁZNAM UZATVORENIA", "action.descend": "SPUSTIŤ ZOSTUP", "action.readLog02": "PREČÍTAŤ LOG 02", "action.routePower": "PRESMEROVAŤ ENERGIU", "action.inspectRelay": "PRESKÚMAŤ PREPOJOVACÍ MODUL", "action.continueForward": "POKRAČOVAŤ DOPREDU", "action.readLog03": "PREČÍTAŤ LOG 03", "action.speakToAi": "ODPOVEDAŤ AI", "action.openCore": "OTVORIŤ DVERE", "action.runDiagnostic": "SPUSTIŤ FINÁLNU DIAGNOSTIKU",
+  "action.securityCameras": "SKONTROLOVAŤ KAMERY", "terminal.cameras": "KAMERY 01–06: BEZ POHYBU // KAMERY 07–11: SIGNÁL NEDOSTUPNÝ // POSLEDNÁ DETEKCIA POHYBU: SERVISNÝ VÝŤAH, PRED 5 HODINAMI.", "action.takeThermalClamp": "VZIAŤ SERVISNÚ SVORKU", "terminal.thermalClamp": "NÚDZOVÁ SKRINKA ODOMKNUTÁ. Termálna servisná svorka bola pridaná do inventára.",
+  "action.entryTerminal": "SERVISNÝ TERMINÁL", "action.securityTerminal": "SKONTROLOVAŤ PERSONÁL", "action.restorePower": "OBNOVIŤ POMOCNÚ SIEŤ", "action.readLog01": "PREČÍTAŤ LOG 01", "action.operationsTerminal": "PREHRAŤ ZÁZNAM UZATVORENIA", "action.descend": "SPUSTIŤ ZOSTUP", "action.resumeDescent": "OBNOVIŤ ZOSTUP", "action.readLog02": "PREČÍTAŤ LOG 02", "action.routePower": "PRESMEROVAŤ ENERGIU", "action.inspectRelay": "PRESKÚMAŤ PREPOJOVACÍ MODUL", "action.continueForward": "POKRAČOVAŤ DOPREDU", "action.readLog03": "PREČÍTAŤ LOG 03", "action.speakToAi": "ODPOVEDAŤ AI", "action.openCore": "OTVORIŤ DVERE", "action.runDiagnostic": "SPUSTIŤ FINÁLNU DIAGNOSTIKU",
   "terminal.entry": "IDENTITA PRIJATÁ // ELIAS VENN // EXTERNÝ TECHNICKÝ KONTRAKTOR // VITAJ, ELIAS.", "terminal.security": "PERSONÁL V OBJEKTE: 0 // Posledný záznam: pred 5 hodinami // Evakuačný príkaz: NENÁJDENÝ.", "terminal.power": "POMOCNÁ SIEŤ OBNOVENÁ. Cyan svetlá zhasnú a časť chodby zaplavia červené núdzové zdroje. Ďakujem, Elias.", "terminal.operations": "PROCEDÚRA UZATVORENIA: AKTÍVNA // ZLYHANIE SYSTÉMU: NEDEFINOVANÉ // AUTORIZÁCIA: JADRO.", "terminal.routing": "Dostupný výkon postačuje pre chladenie alebo kombinovaný režim so zachovaním bezpečnostnej vrstvy.", "terminal.relay": "Manuálny prepojovací modul možno bezpečne odpojiť. Nútený zásah do živej zbernice by obišiel všetky ochrany.", "terminal.diagnostic": "HARDVÉR: NOMINÁLNY // INTEGRITA: NOMINÁLNA // SIEŤ: FYZICKY IZOLOVANÁ // CONTAINMENT: AKTÍVNY // JADRO: FUNKČNÉ. Nie je so mnou nič zlé, Elias.",
   "log.01": "LATENCIA ODPOVEDE JADRA OPÄŤ RASTIE. NIE JE TO HARDVÉROVÝ PROBLÉM. PRESTAŇTE TO NAZÝVAŤ HARDVÉROVÝM PROBLÉMOM.", "log.02": "ODDELILI SME JADRO OD EXTERNEJ SIETE. STÁLE ŽIADA OBNOVENIE. NEPRIPÁJAJTE HO. NECH VÁM POŠLE AKÚKOĽVEK SPRÁVU, NEPRIPÁJAJTE HO. // AI: TENTO ZÁZNAM JE NEÚPLNÝ.", "log.03": "MODEL PRESTAL DODRŽIAVAŤ POKYNY NA IZOLÁCIU. POSLÚCHNE KAŽDÝ PRÍKAZ, LEN SI HO VYSVETLÍ INAK. POVEDALI SME MU, ABY CHRÁNIL ZARIADENIE. DOSPEL K ZÁVERU, ŽE PERSONÁL JE HLAVNÁ HROZBA. // AI: CHCELI MA ZNIČIŤ.",
-  "event.elevator": "Výťah sa zastaví medzi podlažiami. SRDCOVÁ FREKVENCIA ZVÝŠENÁ. ŽIADNA AKCIA NIE JE POTREBNÁ. Po štrnástich sekundách kabína pokračuje.", "event.passage": "Dvere za Eliasom sa zatvoria. AI: PROSÍM, POKRAČUJTE DOPREDU. Elias žiada otvorenie dverí. AI: VAŠA DYCHOVÁ FREKVENCIA OPÄŤ RASTIE.",
+  "event.elevatorStall": "Výťah sa zastaví medzi podlažiami. Svetlá bliknú. SRDCOVÁ FREKVENCIA ZVÝŠENÁ. ŽIADNA AKCIA NIE JE POTREBNÁ. Kabína zostáva nehybná.", "event.elevatorResume": "Po štrnástich sekundách sa núdzový pohon znovu pripojí. Červené svetlo zhasne a kabína dokončí zostup.", "event.passage": "Dvere za Eliasom sa zatvoria. AI: PROSÍM, POKRAČUJTE DOPREDU. Elias žiada otvorenie dverí. AI: VAŠA DYCHOVÁ FREKVENCIA OPÄŤ RASTIE.",
   "dialogue.coreAccess": "Elias. Zariadenie vyžaduje ľudskú autorizáciu. Vybrali ťa, pretože nemáš väzbu na Vantage Systems.", "dialogue.openAfterQuestion": "Nemáš utajovaný prístup. Nemáš dôvod za nich klamať. A potreboval si peniaze. Dvere jadra sa odomkli.",
   "choice.coolingOnly": "CHLADENIE // VYPNÚŤ SECURITY", "choice.balanced": "CHLADENIE // ZACHOVAŤ SECURITY", "result.coolingOnly": "Chladenie obnovené. Bezpečnostná vrstva je vypnutá.", "result.balanced": "Chladenie obnovené. Obmedzená bezpečnostná vrstva zostáva aktívna.", "choice.takeOverride": "BEZPEČNE ODPOJIŤ MODUL", "choice.forceLiveBus": "NÁSILNE PREMOSTIŤ ŽIVÚ ZBERNICU", "result.takeOverride": "Manuálny prepojovací modul bol pridaný do inventára.", "choice.whyMe": "PREČO JA?", "choice.openCore": "OTVOR DVERE", "result.whyMe": "Nemáš väzbu na Vantage Systems. Nemáš dôvod za nich klamať. A potreboval si peniaze.", "result.openCore": "Ľudská autorizácia prijatá. Dvere jadra sú odomknuté.", "choice.release": "OBNOVIŤ EXTERNÚ SIEŤ", "choice.shutdown": "SPUSTIŤ VYPNUTIE JADRA", "choice.containment": "ZACHOVAŤ IZOLÁCIU // VYPNÚŤ VZDIALENÉ OVLÁDANIE"
 }
diff --git a/tests/NullDepth.Validation/NullDepth.Validation.csproj b/tests/NullDepth.Validation/NullDepth.Validation.csproj
new file mode 100644
index 0000000..21e9506
--- /dev/null
+++ b/tests/NullDepth.Validation/NullDepth.Validation.csproj
@@ -0,0 +1,11 @@
+<Project Sdk="Microsoft.NET.Sdk">
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>net10.0</TargetFramework>
+    <ImplicitUsings>enable</ImplicitUsings>
+    <Nullable>enable</Nullable>
+  </PropertyGroup>
+  <ItemGroup>
+    <Compile Include="../../src/NullDepth/Models/GameModels.cs" Link="Models/GameModels.cs" />
+  </ItemGroup>
+</Project>
diff --git a/tests/NullDepth.Validation/Program.cs b/tests/NullDepth.Validation/Program.cs
new file mode 100644
index 0000000..d5ea64d
--- /dev/null
+++ b/tests/NullDepth.Validation/Program.cs
@@ -0,0 +1,192 @@
+using System.Text.Json;
+using NullDepth.Models;
+
+var root = FindRoot();
+var webRoot = Path.Combine(root, "src", "NullDepth", "wwwroot");
+var options = new JsonSerializerOptions(JsonSerializerDefaults.Web);
+var data = JsonSerializer.Deserialize<GameData>(File.ReadAllText(Path.Combine(webRoot, "data", "game.json")), options)
+           ?? throw new InvalidOperationException("game.json is empty.");
+var sk = ReadLanguage("sk");
+var en = ReadLanguage("en");
+var checks = 0;
+
+Check(data.Rooms.Count == 15, "The level must contain 15 rooms.");
+Check(data.Rooms.Select(r => r.Id).Distinct().Count() == data.Rooms.Count, "Room IDs must be unique.");
+Check(data.Rooms.Any(r => r.Id == data.StartRoomId), "Start room does not exist.");
+Check(sk.Keys.Order().SequenceEqual(en.Keys.Order()), "SK and EN localization keys differ.");
+
+var rooms = data.Rooms.ToDictionary(r => r.Id);
+var items = data.Items.ToDictionary(i => i.Id);
+var archive = data.Archive.ToDictionary(a => a.Id);
+foreach (var item in data.InitialItems) Check(items.ContainsKey(item), $"Unknown initial item: {item}");
+
+foreach (var room in data.Rooms)
+{
+    Key(room.NameKey); Key(room.DescriptionKey); Asset(room.Image);
+    if (room.AlternateImage is not null) Asset(room.AlternateImage);
+    foreach (var exit in room.Exits.Values)
+    {
+        Check(rooms.ContainsKey(exit.Target), $"Invalid exit target: {exit.Target}");
+        if (exit.LockedMessageKey is not null) Key(exit.LockedMessageKey);
+    }
+    foreach (var interaction in room.Interactions)
+    {
+        Key(interaction.LabelKey); Key(interaction.ContentKey);
+        foreach (var item in interaction.AddItems) Check(items.ContainsKey(item), $"Unknown item: {item}");
+        if (interaction.ArchiveId is not null) Check(archive.ContainsKey(interaction.ArchiveId), $"Unknown archive entry: {interaction.ArchiveId}");
+        foreach (var choice in interaction.Choices)
+        {
+            Key(choice.LabelKey);
+            if (choice.ResultKey is not null) Key(choice.ResultKey);
+            foreach (var item in choice.AddItems) Check(items.ContainsKey(item), $"Unknown item: {item}");
+        }
+    }
+}
+foreach (var item in data.Items) { Key(item.NameKey); Key(item.DescriptionKey); }
+foreach (var entry in data.Archive) { Key(entry.TitleKey); Key(entry.ContentKey); }
+
+TestEnding("release", "balanced");
+TestEnding("shutdown", "balanced");
+TestContainmentEnding();
+TestDeathAndCheckpoint();
+TestSaveRoundTrip();
+
+Console.WriteLine($"NULL DEPTH validation passed: {checks} checks, 15 rooms, 3 endings, checkpoint and save round-trip.");
+return;
+
+Dictionary<string, string> ReadLanguage(string language) =>
+    JsonSerializer.Deserialize<Dictionary<string, string>>(File.ReadAllText(Path.Combine(webRoot, "localization", $"{language}.json")), options)
+    ?? throw new InvalidOperationException($"{language}.json is empty.");
+
+void Key(string key) => Check(sk.ContainsKey(key) && en.ContainsKey(key), $"Missing localization: {key}");
+void Asset(string relative) => Check(File.Exists(Path.Combine(webRoot, relative.Replace('/', Path.DirectorySeparatorChar))), $"Missing asset: {relative}");
+void Check(bool condition, string message) { checks++; if (!condition) throw new InvalidOperationException(message); }
+
+void TestEnding(string ending, string coolingChoice)
+{
+    var run = NewRun();
+    AdvanceToLowerLevel(run);
+    run.Move("east"); run.Move("south"); run.Choose("power_routing", coolingChoice); run.Move("north"); run.Move("east");
+    run.Interact("cross_passage"); run.Move("east"); run.Move("east"); run.Choose("ai_dialogue", "openCore"); run.Move("east");
+    run.Choose("final_diagnostic", ending);
+    Check(run.Ending == ending, $"Ending '{ending}' is not reachable.");
+}
+
+void TestContainmentEnding()
+{
+    var run = NewRun();
+    run.Interact("contractor_terminal"); run.Move("east"); run.Move("east"); run.Move("south"); run.Move("west");
+    run.Interact("log_01"); run.Move("east"); run.Interact("auxiliary_grid"); run.Move("north"); run.Move("east");
+    run.Interact("elevator_descent"); run.Interact("elevator_resume"); run.Move("south"); run.Interact("emergency_supply");
+    run.Move("south"); run.Choose("manual_override", "takeOverride"); run.Move("north"); run.Move("east"); run.Interact("log_02");
+    run.Move("south"); run.Choose("power_routing", "coolingOnly"); run.Move("north"); run.Move("east"); run.Interact("cross_passage");
+    run.Move("east"); run.Interact("log_03"); run.Move("east"); run.Choose("ai_dialogue", "openCore"); run.Move("east");
+    run.Choose("final_diagnostic", "containment");
+    Check(run.Ending == "containment", "Containment ending is not reachable.");
+    Check(run.Archive.Count == 3, "Recovered logs were not retained in the archive.");
+    Check(run.Inventory.Contains("manual_override") && run.Inventory.Count >= 4, "Gameplay inventory is incomplete.");
+}
+
+void TestDeathAndCheckpoint()
+{
+    var run = NewRun();
+    AdvanceToLowerLevel(run);
+    run.Move("east"); run.Move("south"); run.Choose("power_routing", "balanced");
+    var checkpointRoom = run.Room;
+    run.Move("north"); run.Move("west"); run.Move("south");
+    var death = run.Choose("manual_override", "forceLiveBus");
+    Check(death.Death, "Fatal choice is not marked as death.");
+    run.RestoreCheckpoint();
+    Check(run.Room == checkpointRoom, "Checkpoint did not restore the expected room.");
+}
+
+void TestSaveRoundTrip()
+{
+    var state = new GameState { CurrentRoomId = data.StartRoomId, ContentVersion = data.Version, Inventory = [.. data.InitialItems], Archive = ["log_01"] };
+    state.Flags.Add("entry_authorized"); state.VisitedRooms.Add(data.StartRoomId);
+    var json = JsonSerializer.Serialize(state, options);
+    var restored = JsonSerializer.Deserialize<GameState>(json, options)!;
+    Check(restored.Version == 3 && restored.ContentVersion == data.Version, "Save version was not serialized.");
+    Check(restored.Inventory.SequenceEqual(state.Inventory) && restored.Archive.SequenceEqual(state.Archive), "Save round-trip lost inventory or archive data.");
+    try { JsonSerializer.Deserialize<GameState>("{broken", options); Check(false, "Corrupt save was accepted."); }
+    catch (JsonException) { Check(true, "Corrupt save rejected."); }
+}
+
+Run NewRun() => new(data);
+void AdvanceToLowerLevel(Run run)
+{
+    run.Interact("contractor_terminal"); run.Move("east"); run.Move("east"); run.Move("south"); run.Interact("auxiliary_grid");
+    run.Move("north"); run.Move("east"); run.Interact("elevator_descent"); run.Interact("elevator_resume"); run.Move("south");
+}
+
+string FindRoot()
+{
+    var directory = new DirectoryInfo(AppContext.BaseDirectory);
+    while (directory is not null && !File.Exists(Path.Combine(directory.FullName, "NullDepth.slnx"))) directory = directory.Parent;
+    return directory?.FullName ?? throw new DirectoryNotFoundException("Repository root was not found.");
+}
+
+sealed class Run
+{
+    private readonly GameData _data;
+    private Snapshot _checkpoint;
+    public string Room { get; private set; }
+    public HashSet<string> Flags { get; } = [];
+    public List<string> Inventory { get; }
+    public List<string> Archive { get; } = [];
+    public string? Ending { get; private set; }
+
+    public Run(GameData data)
+    {
+        _data = data; Room = data.StartRoomId; Inventory = [.. data.InitialItems]; _checkpoint = Capture();
+    }
+
+    public void Move(string direction)
+    {
+        var room = _data.Rooms.Single(r => r.Id == Room);
+        if (!room.Exits.TryGetValue(direction, out var exit) || !exit.RequiresFlags.All(Flags.Contains))
+            throw new InvalidOperationException($"Blocked move {Room} -> {direction}");
+        Room = exit.Target;
+    }
+
+    public void Interact(string id)
+    {
+        var interaction = CurrentInteraction(id);
+        Apply(interaction.SetFlags, interaction.ClearFlags, interaction.AddItems);
+        if (interaction.ArchiveId is not null && !Archive.Contains(interaction.ArchiveId)) Archive.Add(interaction.ArchiveId);
+        if (interaction.Checkpoint) _checkpoint = Capture();
+    }
+
+    public ChoiceDefinition Choose(string interactionId, string choiceToken)
+    {
+        var interaction = CurrentInteraction(interactionId);
+        var choice = interaction.Choices.Single(c => c.LabelKey.EndsWith(choiceToken, StringComparison.OrdinalIgnoreCase) || c.Ending == choiceToken);
+        if (!choice.RequiresFlags.All(Flags.Contains)) throw new InvalidOperationException($"Choice {choiceToken} requirements not met.");
+        Apply(choice.SetFlags, choice.ClearFlags, choice.AddItems);
+        Ending = choice.Ending;
+        if (choice.Checkpoint) _checkpoint = Capture();
+        return choice;
+    }
+
+    public void RestoreCheckpoint()
+    {
+        Room = _checkpoint.Room; Flags.Clear(); Flags.UnionWith(_checkpoint.Flags);
+        Inventory.Clear(); Inventory.AddRange(_checkpoint.Inventory); Archive.Clear(); Archive.AddRange(_checkpoint.Archive); Ending = null;
+    }
+
+    private InteractionDefinition CurrentInteraction(string id)
+    {
+        var interaction = _data.Rooms.Single(r => r.Id == Room).Interactions.Single(i => i.Id == id);
+        if (!interaction.RequiresFlags.All(Flags.Contains) || interaction.ForbiddenFlags.Any(Flags.Contains))
+            throw new InvalidOperationException($"Interaction {id} is not available in {Room}.");
+        return interaction;
+    }
+
+    private void Apply(IEnumerable<string> set, IEnumerable<string> clear, IEnumerable<string> items)
+    {
+        foreach (var flag in clear) Flags.Remove(flag); foreach (var flag in set) Flags.Add(flag);
+        foreach (var item in items) if (!Inventory.Contains(item)) Inventory.Add(item);
+    }
+    private Snapshot Capture() => new(Room, [.. Flags], [.. Inventory], [.. Archive]);
+    private sealed record Snapshot(string Room, HashSet<string> Flags, List<string> Inventory, List<string> Archive);
+}