Animating stars (slowly) when not moving as well.

src/game/animation.zig

@@ -28,6 +28,15 @@ pub const Animation = struct {
         return self.sprite.frames[self.current];
     }
 
+    pub fn currentFrameOffset(self: *Animation, offset: usize) allegro.Bitmap {
+        return self.sprite.frames[self.currentOffset(offset)];
+    }
+
+    pub fn currentOffset(self: Animation, offset: usize) usize {
+        const n = self.end - self.begin;
+        return self.begin + (self.current + offset - self.begin) % n;
+    }
+
     pub fn reset(self: *Animation) void {
         self.current = self.begin;
     }
@@ -38,9 +47,6 @@ pub const Animation = struct {
         const skip = @floatToInt(usize, @divFloor(delta, self.interval));
         self.lastUpdate = t - @rem(delta, self.interval);
 
-        self.current = (self.current + skip);
-        while (self.current >= self.end) {
-            self.current = self.begin;
-        }
+        self.current = self.currentOffset(skip);
     }
 };

src/game/game.zig

@@ -12,12 +12,15 @@ pub const Game = struct {
 
     level: Level,
     health: i64 = 4,
+
     playerPosition: engine.PointF,
     playerIdleAnimation: Animation,
     playerWalkingAnimation: Animation,
     playerDirection: Direction,
     isPlayerWalking: bool,
 
+    starAnimation: Animation,
+
     renderer: *Renderer,
     // current viewport translated to tiles.
     boundsInTiles: engine.RectangleF,
@@ -31,6 +34,7 @@ pub const Game = struct {
             .playerWalkingAnimation = Animation.initPartialLoop(renderer.sprites.get("character_lion_48").?, 0.125, 4, 8),
             .playerDirection = Direction.Right,
             .isPlayerWalking = false,
+            .starAnimation = Animation.init(renderer.sprites.get("item_star_32").?, 0.15),
             .renderer = renderer,
             .boundsInTiles = Game.calculateBoundsInTiles(playerPosition),
         };

src/game_scene.zig

@@ -26,7 +26,7 @@ pub const GameScene = struct {
     }
 
     pub fn tick(self: *GameScene, ctx: *Context, t: f32, dt: f32) void {
-        const speed: f32 = 5; // tiles/s
+        const speed: f32 = 6; // tiles/s
 
         if (ctx.keys.isKeyPressed(allegro.c.ALLEGRO_KEY_LEFT)) {
             self.game.moveCharacter(-speed * dt);
@@ -41,6 +41,7 @@ pub const GameScene = struct {
             self.game.isPlayerWalking = false;
             self.game.playerIdleAnimation.tick(t);
         }
+        self.game.starAnimation.tick(t);
     }
 
     pub fn render(self: *GameScene, ctx: *Context) void {
@@ -90,7 +91,7 @@ pub const GameScene = struct {
                     switch (collectable) {
                         game.Level.Collectable.Star => {
                             const distanceToPlayer = engine.Point.init(x, y).float().distance(self.game.playerPosition);
-                            self.game.drawSpriteFrame("item_star_32", @floatToInt(usize, @mod(distanceToPlayer * 0.54, 1) * 16), x, y);
+                            self.game.drawSpriteFrame("item_star_32", self.game.starAnimation.currentOffset(@floatToInt(usize, @mod(distanceToPlayer * 0.54, 1) * 16)), x, y);
                         },
                     }
                 }