Support versioning on save.

src/Murder/Assets/Save/SaveDataAsset.cs

@@ -61,6 +61,11 @@ public class SaveData : GameAsset
         /// </summary>
         public string SaveName { get; init; } = string.Empty;
 
+        /// <summary>
+        /// Game version, used for game save compatibility.
+        /// </summary>
+        public readonly float SaveVersion;
+
         /// <summary>
         /// This is save path, used by its assets.
         /// </summary>
@@ -77,11 +82,13 @@ public class SaveData : GameAsset
         [JsonConstructor]
         public SaveData() { }
 
-        protected SaveData(string name, BlackboardTracker tracker)
+        protected SaveData(string name, float version, BlackboardTracker tracker)
         {
             Guid = Guid.NewGuid();
             Name = Guid.ToString();
 
+            SaveVersion = version;
+
             SaveName = name;
 
             FilePath = Path.Join(Name, $"{Name}.json");
@@ -90,7 +97,7 @@ protected SaveData(string name, BlackboardTracker tracker)
             BlackboardTracker = tracker;
         }
 
-        public SaveData(string name) : this(name, new BlackboardTracker()) { }
+        public SaveData(string name, float version) : this(name, version, new BlackboardTracker()) { }
 
         /// <summary>
         /// Get a world asset to instantiate in the game.

src/Murder/Core/Particles/ParticleSystemTracker.cs

@@ -55,6 +55,7 @@ public ParticleSystemTracker(Emitter emitter, Particle particle, int seed = 0)
         /// </summary>
         /// <param name="allowSpawn">Whether spawning new entities is allowed, e.g. the entity is not deactivated.</param>
         /// <param name="emitterPosition">Emitter position in game where the particles are fired from.</param>
+        /// <param name="id">Entity id, used when generating the correct seed for the particle.</param>
         /// <returns>Returns whether the emitter is still running.</returns>
         public bool Step(bool allowSpawn, Vector2 emitterPosition, int id)
         {

src/Murder/Data/GameDataManager_Save.cs

@@ -17,7 +17,7 @@ public partial class GameDataManager
         /// Creates an implementation of SaveData for the game.
         /// </summary>
         protected virtual SaveData CreateSaveData(string name = "_default") =>
-            _game is not null ? _game.CreateSaveData(name) : new SaveData(name);
+            _game is not null ? _game.CreateSaveData(name) : new SaveData(name, _game?.Version ?? 0);
 
         /// <summary>
         /// Directory used for saving custom data.
@@ -367,10 +367,16 @@ public bool LoadAllSaves()
 
         public bool LoadSaveAtPath(string path)
         {
-            foreach (var asset in FetchAssetsAtPath(path, recursive: false, stopOnFailure: true))
+            foreach (GameAsset asset in FetchAssetsAtPath(path, recursive: false, skipFailures: false, stopOnFailure: true))
             {
                 if (asset is SaveData saveData)
                 {
+                    if (saveData.SaveVersion < _game?.Version)
+                    {
+                        // Skip loading saves with incompatible version, for now.
+                        continue;
+                    }
+
                     _allSavedData.Add(saveData.Guid, saveData);
                 }
             }

src/Murder/IMurderGame.cs

@@ -52,7 +52,7 @@ public void OnExit() { }
         /// <summary>
         /// Creates save data for the game.
         /// </summary>
-        public SaveData CreateSaveData(string name) => new(name);
+        public SaveData CreateSaveData(string name) => new(name, Version);
 
         /// <summary>
         /// Creates the client custom sound player.
@@ -81,5 +81,10 @@ public RenderContext CreateRenderContext(GraphicsDevice graphicsDevice, Camera2D
         /// This is the name of the game, used when creating assets and loading save data.
         /// </summary>
         public string Name { get; }
+
+        /// <summary>
+        /// This is the version of the game, used when checking for save compatibility.
+        /// </summary>
+        public float Version => 0;
     }
 }