feat: add bounce animation to coin collectable

CHANGELOG.md

@@ -6,6 +6,23 @@
 
 ### Added
 
+- **Coin bounce animation**: Coins now bounce upward when collected, providing satisfying
+  visual feedback with a parabolic arc animation (0.4s, 2 tiles high)
+
+### Fixed
+
+- **Java plugin dependency**: Removed Java plugin as a required dependency to improve
+  compatibility
+
+### Changed
+
+- **Coordinate calculations**: Reduced code duplication in rendering coordinate
+  calculations
+
+## [0.2.2] - 2026-04-06
+
+### Added
+
 - **Debug render mode**: Added an optional in-editor debug overlay for game rendering
 - **FPS counter**: Show current renderer FPS inside debug mode
 

src/main/kotlin/dev/stillya/vpet/game/WorldUpdate.kt

@@ -5,12 +5,14 @@ import dev.stillya.vpet.game.ecs.Physics
 import dev.stillya.vpet.game.ecs.SpatialGrid
 import dev.stillya.vpet.game.ecs.World
 import dev.stillya.vpet.game.ecs.components.Collectible
+import dev.stillya.vpet.game.ecs.components.Collecting
 import dev.stillya.vpet.game.ecs.components.PhaseState
 import dev.stillya.vpet.game.ecs.components.PhysicsState
 import dev.stillya.vpet.game.ecs.components.SpriteState
 import dev.stillya.vpet.game.ecs.components.Transform
 import dev.stillya.vpet.game.ecs.components.Velocity
 import dev.stillya.vpet.game.ecs.systems.AnimationSystem
+import dev.stillya.vpet.game.ecs.systems.CollectionSystem
 import dev.stillya.vpet.game.ecs.systems.CollisionSystem
 import dev.stillya.vpet.game.input.InputState
 import dev.stillya.vpet.game.physics.PhysicsBody
@@ -68,9 +70,15 @@ object WorldUpdate {
 		var scoreGain = 0
 		for (id in collected) {
 			val collectible = reg.get<Collectible>(id)
-			if (collectible != null) scoreGain += collectible.value
-			reg.markForRemoval(id)
+			val entityTransform = reg.get<Transform>(id)
+			if (collectible != null && entityTransform != null) {
+				scoreGain += collectible.value
+				reg.add(id, Collecting(startY = entityTransform.y))
+				reg.remove<Collectible>(id)
+			}
 		}
+
+		CollectionSystem.updateCollecting(reg, dt)
 		reg.flushRemovals()
 
 		AnimationSystem.updateAnimations(reg, dt)

src/main/kotlin/dev/stillya/vpet/game/ecs/EntityRegistry.kt

@@ -37,6 +37,14 @@ class EntityRegistry {
 	fun <T : Any> has(id: EntityID, type: KClass<T>): Boolean =
 		components[id]?.containsKey(type) == true
 
+	inline fun <reified T : Any> remove(id: EntityID) {
+		remove(id, T::class)
+	}
+
+	fun <T : Any> remove(id: EntityID, type: KClass<T>) {
+		components[id]?.remove(type)
+	}
+
 	fun allWith(vararg types: KClass<*>): List<EntityID> =
 		components.entries
 			.filter { (_, comps) -> types.all { it in comps } }

src/main/kotlin/dev/stillya/vpet/game/ecs/components/Collecting.kt

@@ -0,0 +1,6 @@
+package dev.stillya.vpet.game.ecs.components
+
+data class Collecting(
+	val startY: Float,
+	val elapsed: Float = 0f
+)

src/main/kotlin/dev/stillya/vpet/game/ecs/systems/CollectionSystem.kt

@@ -0,0 +1,32 @@
+package dev.stillya.vpet.game.ecs.systems
+
+import dev.stillya.vpet.game.ecs.EntityRegistry
+import dev.stillya.vpet.game.ecs.components.Collecting
+import dev.stillya.vpet.game.ecs.components.Transform
+import kotlin.math.pow
+
+object CollectionSystem {
+	private const val BOUNCE_DURATION = 0.4f
+	private const val BOUNCE_HEIGHT = 2.0f
+
+	fun updateCollecting(registry: EntityRegistry, dt: Float) {
+		val collectingEntities = registry.allWith(Collecting::class, Transform::class)
+
+		for (id in collectingEntities) {
+			val collecting = registry.get<Collecting>(id) ?: continue
+			val transform = registry.get<Transform>(id) ?: continue
+
+			val newElapsed = collecting.elapsed + dt
+
+			if (newElapsed >= BOUNCE_DURATION) {
+				registry.markForRemoval(id)
+			} else {
+				val progress = newElapsed / BOUNCE_DURATION
+				val bounceOffset = BOUNCE_HEIGHT * (1 - (2 * progress - 1).pow(2))
+
+				registry.add(id, transform.copy(y = collecting.startY - bounceOffset))
+				registry.add(id, collecting.copy(elapsed = newElapsed))
+			}
+		}
+	}
+}

src/main/kotlin/dev/stillya/vpet/game/rendering/RenderSystem.kt

@@ -96,6 +96,8 @@ class RenderSystem(
 			if (frames.isEmpty()) continue
 
 			val coinLine = t.y.toTileInt()
+			if (coinLine < 0) continue
+
 			val lineFrac = t.y - coinLine
 			val baseY = editor.logicalPositionToXY(LogicalPosition(coinLine, 0)).y
 			val pixelY = baseY + (lineFrac * lineHeight).toInt()

src/test/kotlin/dev/stillya/vpet/game/WorldUpdateTest.kt

@@ -11,6 +11,7 @@ import dev.stillya.vpet.game.ecs.Physics
 import dev.stillya.vpet.game.ecs.World
 import dev.stillya.vpet.game.ecs.components.AnimationComponent
 import dev.stillya.vpet.game.ecs.components.Collectible
+import dev.stillya.vpet.game.ecs.components.Collecting
 import dev.stillya.vpet.game.ecs.components.PhaseState
 import dev.stillya.vpet.game.ecs.components.PhysicsState
 import dev.stillya.vpet.game.ecs.components.SpriteState
@@ -131,7 +132,9 @@ class WorldUpdateTest {
 		val (frame, _) = WorldUpdate.tick(world, InputState(), 0.016f, character, tileMap, 0..10)
 
 		assertEquals(initialScore + 1, frame.world.score)
-		assertTrue("Collected bug should be removed", !frame.world.registry.exists(bug))
+		assertTrue("Collected bug should still exist during bounce", frame.world.registry.exists(bug))
+		assertTrue("Collected bug should have Collecting component", frame.world.registry.has<Collecting>(bug))
+		assertTrue("Collected bug should not have Collectible component", !frame.world.registry.has<Collectible>(bug))
 	}
 
 	@Test