just_game_engine 2.0.0-dev.1

A game engine for Flutter: 2D, with 3D graphics and physics to opt into; ECS, level maps, sprites and animator graphs, timelines, virtual cameras, particles, audio and input.

Changelog

All notable changes to the Just Game Engine will be documented in this file.

2.0.0-dev.1 - 2026-10-15

A dev release of 2.0.0, a breaking release. The engine is now an object a game creates, initializes and disposes, with its own registries, loaders and world. Levels are JSON scenes described by component definitions that the game and an editor share. Cameras, input, sprites, tile maps, animation and the transform hierarchy were rebuilt, and the game services moved to a package of their own. 3-D graphics (drawn by just_graphics_engine) and 3-D physics (on Jolt) are there to opt into, on transforms, cameras and render and culling seams built for both. A 2-D game draws, moves and saves as before, and carries none of the 3-D.

Depend on it with just_game_engine: ^2.0.0-dev.1: a ^2.0.0 constraint does not pick up a dev release.

Upgrading from 1.6? Read MIGRATION.md, which has the full lists of removed, renamed and deprecated APIs. Scene files saved by any earlier version still load: they are migrated in memory, format 0 to 9, and nothing on disk changes until you save.

The engine has 1,874 passing tests.

Breaking changes

• Lifecycle: Engine() is an ordinary constructor (Engine.instance and resetInstance() are gone); initialize() throws EngineInitException and undoes what it built; dispose() is async and final; subsystem getters throw EngineNotReadyError outside that window (engine setup).
• Game services (achievements, auth, leaderboards, currency, inventory, ads) moved to just_game_services and are opt-in through EngineConfig(services: ...) (game services).
• Physics: PhysicsSystem(engine.physics) replaces the 1.x solver and PhysicsBridgeSystem. PhysicsBodyComponent is split into RigidBody2D (how a body moves) and Collider2D (its shape), with the names, defaults (friction 0.5, no bounce, damping 0.05, and a mass worked out from the collider when it is 0) and events (CollisionEnter2DEvent, SensorEnter2DEvent, …) of the 3-D bodies; a collider alone is a static body. The joints are DistanceJoint2D, FixedJoint2D, SliderJoint2D and WheelJoint2D. A body has one bodyType and a named layer (0–15) with collidesWith instead of category and mask bits, and its collider follows the entity's scale (physics bodies). Saved scenes keep every old setting.
• Transforms: rotation is angle and rotationX / rotationY are eulerX / eulerY. Every World runs the hierarchy, and destroying a parent destroys its children (transforms, hierarchy).
• Cameras are virtual cameras and a brain; behaviours, CameraFollowComponent, springs, shake and worldBounds are removed (cameras).
• Input comes from just_inputs: engine.input is an InputService, and InputComponent reads actions by name (input).
• Moved or replaced: in-game UI components went to just_ui_editor, the Tiled components to LevelMapComponent, and the legacy animation system and scene graph to sprite animation, timelines and SceneLoader (in-game UI, level maps, sprites, scenes).
• No global instances: localization and effect types live on engine.context, and asset loaders take assets: engine.assets (localization, assets).
• Imports: widgets are in package:just_game_engine/widgets.dart, and re-exported packages use show lists (imports).
• Draw order: RenderSystem sorts by LayerComponent and draws particle emitters itself (draw order).
• Storage: the engine keeps its own storage file and prefixes cache keys; entries written with setString / setJson before 2.0 are not read (storage).
• Removed and renamed: the networking stubs, the Steam and Epic providers, the Reactive*Components and the particle shape / gravity deprecated in 1.6, and AudioListenerComponent's fixed forwardX … upZ directions (the entity's rotation, atCamera and faceCamera say where the listener is and which way it faces); AssetBundle is GameAssetBundle, typedef Easing is EasingFunction and SystemPriorities.tileMap is levelMap (removed, renamed).
• Audio is played and controlled by calls, not components: AudioPlayComponent, AudioPauseComponent, AudioResumeComponent and AudioStopComponent are gone. AudioSystem.playOneShot(...) plays a sound once, and play(), pause(), resume() and stop() on an AudioSourceComponent or AudioStreamComponent control it (AudioRequests), so a sound no longer changes the world's structure twice. The system no longer clears playOnAdd when it starts a sound — it remembers what it started — so a scene an editor saves keeps its sounds starting (audio).
• A switched-off parent switches off its subtree: queries, tag lookups, findEntityByName and the engine's systems go by the new Entity.isActiveInHierarchy; each entity's own isActive (the saved Enabled flag) is kept as it is (behaviour).
• Requires Flutter 3.47.1 or newer, the first stable where Flutter GPU can be switched on in Windows and Linux release builds (for just_graphics_engine). Every app builds the renderer's shaders; a 2-D game never loads them.

Added

• 3-D graphics (package:just_game_engine/graphics_3d.dart): EngineConfig(graphics3D: Graphics3D()) gives the engine ModelComponent, LightComponent, EnvironmentComponent, AnimationPlayerComponent, SocketComponent and the shapes Cube3D to Polygon3D (base Primitive3D), saved in scenes and drawn from the engine's camera by just_graphics_engine on Flutter GPU (GraphicsSceneRenderer, GraphicsModels, GraphicsShapes, AnimationSystem3D, SkeletalAnimationTarget, SkeletalClipTrack). Physics bodies and characters are drawn between their last two poses. A game without a Graphics3D is 2-D only: no GPU device, no shaders loaded, and a scene holding a 3-D component fails to load with an UnknownComponentTypeException whose builtInHint says how to turn 3-D graphics, or 3-D physics, on. Where Flutter GPU can't draw, the game runs anyway, the 3-D view shows a note, and Graphics3D.unsupportedReason and onUnsupported say why. engine.graphics3D is the one given; it starts before the game's own services.
• 3-D physics (package:just_game_engine/physics_3d.dart): EngineConfig(physics3D: Physics3D()) gives the engine RigidBody3D, Collider3D (box, sphere, capsule, cylinder, convex hull, mesh, height field, or matching a 3-D shape), CharacterBody3D and the joints FixedJoint3D, PointJoint3D, HingeJoint3D, SliderJoint3D, DistanceJoint3D and SixDofJoint3D, stepped by PhysicsSystem3D on Jolt Physics (just_physics_engine's JoltPhysicsEngine), with CollisionEnter3DEvent and the rest, Physics3DQueries and the camera's CameraCollisionStage. A game without a Physics3D is 2-D only and its release build carries none of it; the world is made only with the first 3-D body. The app's pubspec builds Jolt (hooks: user_defines: just_jolt: build: true); where 3-D cannot run, initialize() fails with a Physics3DUnsupportedError (Physics3D.isSupported asks first). engine.physics3D is the one given.
• ModelAsset and ModelGeometry: what the engine knows about a 3-D model (bounds, mesh names, CPU triangles for picking and mesh colliders). A renderer registers the loader for AssetType.model.
• SolidShapeSource and its convex SolidParts (SolidBox, SolidSphere, SolidCapsule, SolidCylinder, SolidHull): a component whose look is a solid of known shape says so, and a physics package gives a collider that same shape (just_graphics_engine's 3-D shapes, and a Collider3D set to match the shape).
• Saved formats in pure Dart: SceneFormat and its migrations, TimelineFormat, AnimatorGraph and UnsupportedFormatVersionException now live in just_game_engine_formats, so the editor and the just command-line tool migrate files with the engine's own code. The engine re-exports them: no import changes. New there: SceneStarters (what a new level starts from), SceneManifest (scenes.json) and SceneNames (the naming rules).
• The engine object: EngineConfig (defaultSystems, extensions, services, createRendering, createAudio, and createPhysics, which makes engine.physics, the 2-D physics engine; null keeps the standard one, native Box2D or pure Dart on the web), DefaultSystems.all / headless, Engine.stateListenable, Engine.cursor (the mouse cursor GameWidget shows over the game; SystemMouseCursors.none hides it for mouse-look), and EngineContext: one engine's definitions, field types, migrations, loaders, signals and localization, which a package extends through a ContextExtension.
• A per-frame phase. FrameSystem: a System that also implements frame(deltaTime, alpha) runs once per rendered frame, after the frame's fixed updates and before it is drawn (World.frame, GameLoop.onFrame, SystemManager.registerFrameTask/runFrameCycle). Systems that don't implement it pay nothing.
• Services, plugins and widget layers: EngineService and ServiceHost; EnginePlugin, updated even while paused; GameLayers, which draw real Flutter widgets over the game; GameWidget.overlay.
• Scenes: a ComponentDefinition describes a component's fields, save format and editor hints once, for the game and an editor alike. SceneLoader loads scenes and the scenes.json manifest. Scene format 9, with step-by-step migrations (MigrationHooks, MigrationResult); files from a newer engine are refused with UnsupportedFormatVersionException.
• Level maps: LevelMapComponent (inline, a .map.json, or a Tiled .tmx / .tmj), all four Tiled orientations, sparse chunked layers drawn among the sprites, merged collision bodies (MapCollisionSystem), entities on map layers, run-time edits through LevelMaps.of(...), Wang fills, TiledInterop, and a built-in basicShapes tileset.
• Sprites and animation: SpriteComponent and SpriteAnimationComponent play TexturePacker and Aseprite atlases; AnimatorGraph (.animator.json) state machines read velocity, health and other bindings with no code, crossfade a transition over its duration on targets that can blend, and weigh several clips in a state's blend tree by one or two parameters (AnimatorBlendTree, AnimatorBlendMotion, AnimatorBlendType; a sprite plays a blend tree's heaviest motion and always cuts); one Easings table.
• Animation targets: AnimationTarget and context.animationTargets. An entity with an AnimatorComponent and no sprite plays its graph on the first registered target that drives it (just_graphics_engine registers a model's skeleton).
• Timelines: TimelineAsset and TimelinePlayerComponent with property, sprite-clip, camera-shot, audio, activation, nested and event tracks, each bound to self, a name or a tag; TimelinePlayback for editors. TimelineTrackOffer: a kind of track can say what an editor's Add track menu calls it and how to make an empty one (TimelineTrackKinds.register(offer:), offerFor, offered); the engine's own kinds, but the field-bound property track, are offered.
• Cameras: VirtualCameraComponent and CameraBrain with blends, stages (framing, dolly, group framing, noise, impulses, confiner) and manager cameras (state-driven, blend list, mixer).
• 3-D camera rigs: OrbitFollowComponent (a third-person camera circling its target, turned by yaw/pitch), FirstPersonComponent and LookAtComponent, with their stages (OrbitFollowStage, FirstPersonStage, LookAtStage), definitions and cameraForward/cameraAnglesOf.
• CameraBrain.updateMode: CameraUpdateMode.frame runs the brain once per rendered frame, following targets blended between their last two fixed updates (CameraBrain.sampleTargets, CameraStageContext.targetPosition3, targetRotation and alpha), so a camera follows a body smoothly at any frame rate. fixed is the default.
• CameraRegistries: the camera stages and managers are one set per EngineContext (CameraRegistries.of(context)), so a kit's extension registers its stages once for every brain of an engine. A CameraBrain made on its own keeps a set of its own.
• Input: actions from an input asset across keyboard, mouse, gamepads, touch and on-screen controls; local multiplayer; rebinding saved per player. Input keeps running while the game is paused. LookActions, LookInput and LookSettings (just_inputs) are re-exported: a 3-D game's camera reads its look through them.
• Pointer lock for mouse look (Windows, from just_inputs; PointerLock is re-exported): engine.input.pointerLock holds the mouse in the window and feeds its raw movement to the look actions, and with engine.input.lockPointerOnClick a mouse click on GameWidget takes hold. Escape lets go, whatever widget has the keyboard — GameWidget keeps every key, so a game's own Escape handler above it never saw one.
• 3-D sound. An AudioSourceComponent with is3d is heard from where its entity is: full volume within minDistance, silent beyond maxDistance, faded between by rolloff (AudioRolloff), with dopplerLevel and farCutoff (muffling with distance) — saved in scenes, all of them, with channel and pan (an older scene loads with the defaults). Changing them on a playing source applies at once. AudioSystem.playOneShot(position:, spatial:) does the same for a one-shot. AudioSpatial, AudioRolloff and AudioSpatialMix are re-exported.
• The listener (AudioListenerComponent, saved in scenes): at its entity and facing the way the entity's rotation turns the world's forward, or from the output camera — atCamera, faceCamera (a third-person game puts it on the player, facing like the camera). With no listener, the camera hears. AudioSystem takes the camera (the default systems pass the engine's).
• Tags, targets and spawners: TagComponent holds a set of tags behind a world index (findTagged); EntityTarget, Spawner, SpawnPoints and the project's TagLibrary.
• Rendering: LayerComponent draw order, RenderHookChain, RenderPass, ParallaxRenderSystem, opt-in shape batching and view culling (ViewCullingSystem), and RenderStatsSink. FrameView carries the view's frustum, cameraPosition and cameraForward, and the game loop's interpolation (RenderingEngine.interpolation, set by GameWidget every tick).
• ViewCullingSystem culls by frustum when the camera is in space (isPlanar false): an entity's box is the union of its components' 3-D extents, placed by its full transform; out of view it stays active within activeDistance. A 2-D camera culls by its rectangle.
• Ready for 3-D: WorldAxes, Euler and quaternion transforms (2-D code keeps a plain angle), the hierarchy inside World.update, a camera with depth, pitch, yaw and a perspective lens, and the SceneRenderer, ViewVolume and SpatialIndex seams. See ARCHITECTURE.md.
• Previous poses for 3-D render interpolation: TransformComponent.captureCount (how many times the previous pose was captured, so a renderer can tell a fresh previous pose from a stale one), previousRotationInto (the captured rotation whether the transform was planar or not), capturePreviousWithRotation (for a mover whose entity gameplay turns before the step) and interpolatedToWorldInto (the matrix between the previous pose and the pose). World.updateCount counts updates.
• Physics and gameplay: distance, fixed, slider and wheel joints, joined to the body an EntityTarget names; SimpleMovementComponent; PhysicsLayers, sixteen named layers and a collision grid in assets/project/physics.json; Collider2D shapes (box with rounded corners, circle, capsule, polygon, segment, chain, and matchShape, which follows what the entity draws) with their own offset, rotation and scale; RigidBody2D friction, gravityScale, lockRotation, continuousCollision, canSleep, initial velocities, ground contact, velocities read back and forces from code (addForce, addImpulse, setVelocity, …); CollisionStay2DEvent (opt-in); Physics2DQueries (rays, circle casts, overlaps by layer); ColliderGeometry. CharacterBody2D, the 2-D twin of CharacterBody3D: a capsule or a box gameplay moves (moveVelocity, jump) that walks slopes up to a steepest angle, climbs steps, keeps to the floor going down, rides moving platforms, stands on one-way platforms and jumps up through them, and pushes dynamic bodies — the same on native Box2D and on the web (just_physics_engine's CharacterMover2D). A RigidBody2D of mass 0 weighs what its collider's area says (PhysicsSystem.autoMassPerSquareUnit: a 100 × 100 box weighs 1000 kg, as a 1 m cube does), and a CharacterBody2D 70 kg.
• The package declares all six platforms and builds for the web with dart2js and dart2wasm.
• An entity keeps its components in its own order: Entity.components lists them as they were added — a scene's entity as its file lists them — rather than in the order of the archetype it shares with every entity of the same types, which was whatever came first. Entity.reorderComponents(types) rearranges them (an editor's inspector does) and Entity.componentTypes reads the order. A scene saves it. Systems find components by type, so nothing runs differently.
• Hot reload, for an editor: EngineContext.refreshDefinitions() puts every component definition in place again as the code now makes it — the engine's own, then each installed RefreshableExtension's — so an editor shows a field added to a component without a restart. ComponentDefinitionRegistry.refresh replaces by type and leaves a project's deliberate replacement alone (register(override: true), or one an ifAbsent registration found in place). World.sortSystems() puts a changed System.priority in effect. The engine's definitions (CoreDefinitions, CoreComponentSchemas, CameraDefinitions, LevelMapDefinitions, TimelineDefinitions) are getters rather than static finals, which a hot reload never rebuilds; read one through context.definitions where its identity matters. A game never calls any of this.
• Query versions: World.queryVersion(types) moves only when what that query matches may have changed (an entity with those types made, destroyed, given or rid of a component, or switched on or off), so a system rebuilds what it keeps per entity only when its own queries change. It replaces a world-wide structure counter that moved on any change at all.
• Audio control: AudioSystem.playOneShot(clipPath, ...) (flat, or placed in 3-D with position and spatial), the AudioRequests play(), pause(), resume() and stop() on sources and streams, and Engine.suspendAudio() / resumeAudio() / isAudioSuspended, which GameWidget calls as the app goes to the background and comes back. A timeline's audio track plays through TimelineAudio.viaAudioSystem.
• ECS helpers: Entity.isActiveInHierarchy, Entity.getComponentByType, World.profiling and SystemManager.profiling (on by default except in release builds), System.profileName (the stats key; override it for readable names in web release builds), TransformComponent.setPreviousPose and previousIsPlanar, ComponentDefinitionRegistry.revision, EntitySpatialGrid(maxCellSpan:), ReactiveSystem.unwatchEntity / unwatchAll, and TimeManager.unscaledTotalTime.
• Signal and Computed from just_signals are re-exported: the reactive wrappers return them.
• Dialogue (Yarn): <<set $x to v>> and <<declare $x = v>>; option conditions -> text <<if cond>>; Yarn escapes (\#, \{, \}, \<, \>, \\, \[, \], \/); {$var} in speaker names and command arguments, and quoted command arguments kept whole; expressions with and, or, not, xor, eq, is, neq, gt, gte, lt, lte and + - * / %, in Yarn's precedence (TokenType.commandDeclare, SetStatement.isDeclaration).
• Physics: PhysicsSystem.scaleTolerance and PhysicsSystem3D.scaleTolerance, ColliderGeometry.inertiaOf, PhysicsJointBindingSystem.dartSpring, Physics3D.reloadModel (a model loaded again rebuilds its mesh and hull colliders; Graphics3D calls it), ColliderShapes3D.forgetModel and its cache limits.
• 3-D and rendering: ShapeValues with Primitive3D.writeShapeValues / writeMaterialValues (a custom shape may override them to skip building its key each frame), GraphicsShapes(inUse:), AnimationPlayerComponent.fadingFromSpeed / fadingFromLoop / fadingFromSpeeds, AssetManager.unregisterLoader, CameraStageRegistry.revision, SpriteAssetLoader.callerDisposesImages, and an opt-in CircleParticleRenderer(batched: true) that draws every circle in one atlas draw.
• LocalizationManager.hasTable and tagOf; locale tags keep their script (zh_Hans). Timelines: TimelineContext.endsAt and BlockTrack.blockAt(includeEnd:). Sprite.tintedAlpha and SpriteAtlasPage.dispose.

Changed

The full list is in MIGRATION.md. The ones most likely to matter:

• Entity ids are never reused, Component.onDetach always runs, switching isActive takes effect at once, and CommandBuffer applies commands in the order they were queued.
• Damping slows only a dynamic body, as in 3-D: a kinematic one (a moving platform) keeps the velocity it is given. Box2D slowed it as well.
• Bundle assets are no longer copied into the persistent cache, and CacheManager.clearAll() clears only the engine's own keys.
• Sprite batches honour each sprite's filterQuality, mirroring and stretch; RenderingEngine.stats count the whole frame.
• Wind and noise particle forces give the same values on every platform and advance once per frame, not once per particle.
• Shader effects are skipped with one log line where they are unsupported (the web, Skia) instead of throwing every frame.
• GameWidget resumes only a pause the app lifecycle caused, and wires up an engine that finishes initializing after the widget is built. Its FPS badge keeps clear of a phone's status bar and notch.
• AudioSystem is a FrameSystem: playback starts and stops on the fixed step, but where the listener and 3-D sources are is read once per rendered frame, after the camera has moved. The engine's audio task is a frame task, run last, so every 3-D sound is placed once a frame with what moved; it is not an update task.
• AudioSystem stops a source's sound when the component or its entity goes (a picked-up coin's sparkle used to play on), and when it is removed; a sound that plays to its end sets the source's handle back to null. Nothing plays before the audio engine has started: sources and streams wait (on the web, for the first key or tap, so they don't start a browser's audio context early, silent), and a one-shot asked for before then is dropped.
• just_audio_engine ^1.1.0: 3-D sound worked out the same on every platform, one platform call a frame, the master volume applied once; package assets play, and hot restart, setLoop, cancelFade and iOS work (see its changelog).
• The engine's lifecycle lines (initialized, started, a system registered, disposed, …) print only in debug builds; warnings and errors still print in every build.
• lib/ no longer imports dart:io (except, conditionally, to find its storage folder) or depends on web.
• Children of moving bodies are drawn between their last two poses with their parent: RenderSystem interpolates every transform whose previous pose was captured in the last step (captureCount), and the hierarchy gives a child its previous pose from its parent's. It also settles again after the frame phase, so children of what moved in frame() follow in the same frame.
• While the engine is paused, game time (TimeManager.totalTime, deltaTime) stands still, audio still updates (a volume changed in a pause menu is heard at once), and camera effects such as ScreenFadeEffect and LetterboxEffect run on real time; the camera update task is gone. The per-frame phase gets the frame time clamped to maxDeltaTime.
• RenderSystem is a FrameSystem and takes its interpolation from the frame phase; the engine, not GameWidget, sets RenderingEngine.interpolation.
• A switched-off entity's sound pauses and plays on when it is switched back on; a volume change on a playing source or stream is heard.
• Systems of equal priority run in the order they were added, adding a system twice does nothing, and systems and plugins can be added or removed while they run (a system may remove itself).
• Entity.components is an unmodifiable List; Archetype.getColumn and entityIds are @internal.
• Profiling timings (systemTimesMs, lastUpdateMs) are taken only while profiling is on, so release builds skip them.
• Physics events are per pair of entities: a chain or compound collider sends one enter and one exit, an end and a begin in the same update cancel, and a body rebuilt because its collider, scale or sensor flag changed keeps its contacts instead of entering again. Scale changes smaller than scaleTolerance do not rebuild a body. 2-D joint springs are hertz and damping ratio on every backend; slider and wheel axes are in the joint entity's space. A kinematic RigidBody2D moved through its transform carries what stands on it. Torque and angular impulses turn a 2-D body by its rotational inertia.
• A clip fading out keeps its own speed and looping; set speed / loop for the new clip after play(). CameraState.lerp extrapolates outside 0..1, so blends with overshooting curves overshoot. PlayerScratch and samplePlayer are no longer exported.
• A sprite's tint alpha multiplies its opacity, as a shape's does (it was ignored). An entity without a LayerComponent is ordered by its renderable's own layer and zOrder; the built-in shapes' renderables are on layer 0. Renderable.ySort sorts within its layer (after the rest of its layer and zOrder, by world y), keeps its ShaderComponent and batches.
• Post-process passes and motion blur include the background colour and parallax.
• A timeline block that reaches the end of a once (or ping-pong) timeline holds there, so an activation, sprite clip or camera shot stays as the timeline left it.
• Dialogue conditions follow Yarn: ! binds tightest, and anything unreadable (bare words, visited(), trailing text) is false, with a debug message. A <<set>> that assigns nothing is a YarnParseException. Localization tables for the same locale and namespace merge, and a fallback such as en_US also falls back to en.
• On the web the engine's storage keys sit beside JustStorage.standard()'s rather than among them, so an app's own clear() leaves the engine's cache and settings alone.
• A scene with a value of the wrong type fails with a FormatException naming the entity, component and field (the world is left untouched); a loop of parents in a scene is cut, with a debug message.
• AssetManager keeps assets by path and type (an atlas and its JSON are two), and unload(path) unloads every type at the path; a load that unload, unloadAll or dispose overtakes is not kept; acquire counts at once, so a release while loading counts.

Performance

Drawing 10,000 shapes went from about 19.5 ms to 12.9 ms a frame, and 2,000 physics bodies step and sync in 1.56 ms (test/perf/transform_hot_path_test.dart, Windows, debug JIT). Shapes cache their paints and paths, RenderSystem iterates archetype columns and batches sprites with drawRawAtlas, queries are invalidated per archetype, and audio positions are sent only when they change. A 2-D physics world with no bodies is not stepped (PhysicsEngine.bodyCount). With query versions, spawning and removing unrelated entities no longer makes systems rebuild: preparing 10,000 shapes for drawing while other entities come and go went from 5.3–6.5 ms to about 0.5 ms a frame. Audio one-shots no longer change the world's structure. Release builds skip the per-system timings. The 3-D scene renderer keeps what still stands across structural changes and checks shapes, lights and the environment without allocating; each socket parent is posed once per update. Particle colours no longer allocate per particle, timeline vector channels skip the save codec, the camera brain caches each camera's pipeline, sprite systems look each sprite up once, and the physics systems find each body's shape source once per change instead of every step.

Fixed

• Rendering: batched sprites drew above every layer, and mirrored ones vanished; ParticleEmitterComponent emitters, and RenderableComponent subclasses without componentType, were never drawn; a replaced ShaderComponent kept its disposed shader; sprite batches, images and shaders leaked.
• Physics: changing bounciness, damping, friction, isSensor or shape at run time reached only the Dart side of a native Box2D body; static bodies shook after a scene load; the collider outline ignored the body's turn; a weld joint was not remade when its anchor changed; wheel joints without native support were a slider; RaycastSystem missed default-sized colliders, and ColliderDebuggerSystem's filters also hid raycast outlines.
• Cameras: a standby blend list did not start over when it went live again; emitting the same CameraImpulse twice doubled it; DollyPath.closed and CameraRigMemory.reset() were wrong.
• Maps, animation and timelines: Aseprite ping-pong tags showed a frame twice; hidden Tiled image layers imported as visible, without their parallax and tint; TileChunkData took any number of cells; hidden cells could change without a redraw; AnimatorComponent.getFloat, getInt and getBool misread parameter types; TrackBinding.fromJson and KeyCurve.numberAt mishandled some values.
• Audio: 3-D sources were panned as well; a stream's fade-in did not start from silence; .flac and upper-case extensions went undetected; every sound effect played on the sfx channel, whatever its component's channel said.
• Dialogue: autoAdvance never ran; YarnParser silently cut nodes short on malformed <<if>> blocks (now a YarnParseException); DialogueBoxWidget leaked its old runner's listener.
• Game loop: two GameWidgets showing one engine ran the game about three times too fast (each frame is now counted once, by the vsync frame's timestamp); music and sounds kept playing when the app went to the background; with the dev terminal open, a key held as it opened stayed down; a service added to a running engine and disposed before its start() finished was never stopped.
• ECS: adding or removing a system or plugin while they ran threw; equal-priority systems lost their order past 32 systems; listing an entity's components while it changed showed another entity's; a parent cycle hung the hierarchy (it is now refused with an ArgumentError); TransformComponent(scale:) kept the caller's vector; one failing command dropped the rest of a CommandBuffer batch; ReactiveSystem leaked listeners; EntitySpatialGrid broke on NaN or huge bounds; destroyAllEntities left parent links bound.
• Saving and loading: CacheManager's maxBinaryEntries never evicted anything; two initialize() calls opened the stores twice, and a dispose() during initialize() left the database open; ComponentDefinitionRegistry kept a stale by-type entry after an override or unregister, let an alias shadow a real type, and stopped refreshing the built-ins after they were registered twice; a gradient with one colour or mismatched stops threw on every paint; an enum overriding toString saved its display text; SceneLoader.loadManifest broke on a non-string entry; AssetScope.dispose() during an acquire leaked a count.
• Effects: cancelling from an effect's own callback dropped or repeated others, and cancelAll() there threw; a looping effect fast-forwarded lost its phase; a fade along an overshooting easing ended off target; an absolute PathEffect never reached its waypoints; ScaleEffect flipped mirrored entities; PredictionEffectRuntime duplicated effects on a second rollback.
• 2-D physics: on native Box2D every chain segment fired its own enter and exit and left isGrounded stuck; a body rebuilt by a scale or collider change entered again with no exit (3-D too), and joints on it were remade every step; waking a body never reached Box2D, so a sleeping body ignored a gravity change; a wheel joint orbited the chassis; a static sensor reported static colliders; view culling did not freeze native bodies; angles wrapped at ±π and flicked when drawn; a capsule was too short under non-uniform scale; a ray along a box's edge hit its far side; ColliderDebuggerSystem drew only circles and boxes.
• 3-D: textured shapes flashed white after standing unchanged for a few seconds; a one-shot clip fading out jumped back to its start; sockets were drawn a step ahead of the hand holding them, and each one posed its parent again; a socket parent's posed model leaked once it was destroyed; Graphics3D.stop() left the renderer and model loader behind; a 3-D body refused for a bad layer was never made after the layer was fixed; mesh and hull collider caches grew without limit and kept old triangles after a model reload.
• Cameras and particles: group framing let outlying members leave the shot; a camera a trigger switched on stayed on after the trigger went; GameCameraControls panned the wrong way on a rolled camera; a capped emitter saved up emission, short bursts emitted nothing on a long first frame, and isComplete ignored live sub-emitters; SpriteLoadSystem never disposed the images it owned.
• Rendering: a rolled 2-D camera culled things at the screen's corners (getVisibleBounds is now the box around the turned view); a tinted sprite or parallax layer below full opacity was faded twice and changed opacity when it left a sprite batch; sprites from different atlases on one layer swapped order when batched; a per-entity shader clipped turned sprites' corners; a trimmed atlas frame's anchor was mirrored, and a frame without sourceSize was invisible; unloading an atlas page's image asset left the cached atlas drawing a disposed image.
• Level maps: orthogonal layers with tiles bigger than the grid drew out of order across tilesets, mirrors and chunks; Tiled import dropped the rotation of tile collision objects and could not read tilesets saved before Tiled 0.15; MapGeometry.boundsOf was half a tile short on staggered and hexagonal maps.
• Dialogue and localization: <<set $rich = $gold >= 100>> read one variable named gold >= 100, and "a" == "b" was stored as a string; restarting a runner broke stop(), a command from an old session drove the new one, a call from a signal listener was lost, and a throwing command left the runner running; selectChoice with an invalid index used up the choices; the typewriter split emoji; DialogueManager.startDialogue with a missing node let the error escape; DialogueLocalizer never switched the locale it loaded; tables for one locale replaced each other; plurals mishandled fractional counts and infinity; script codes (zh_Hans / zh_Hant) overwrote each other.
• Timelines: an event handler destroying a later player crashed the update; ping-pong landed wrong on long steps, kept a stale direction after stop / seek, and played its start cue only once; a looping nested block fired an extra lap, and one crossed in a single step never applied its end; forwards() restarted from 0; a sprite clip spanning a loop's wrap froze after one lap; a new timelinePath then play() played the old timeline; a range moved behind the playhead fired events backwards; a colour field keyed without "color": true threw; zero-length timelines did nothing; a signal emitted from a listener was lost; instant (audio) blocks counted their drawn length.
• Audio: starting a sound cleared its playOnAdd, so a scene saved from an editor after the system had run once (the third-person template's level was) never started its loops and music again; sounds still loading survived stopAll(), removing the system and dispose().
• Other: asset bytes ignored their offset; paths with spaces, @, + or non-ASCII characters could not be cached; the dev terminal leaked the backquote and could not type capitals; two component classes with the same name could not share a world; CheckpointSystem drew its radii in the wrong space and crashed without a transform; RayRenderable(lifetime: 0) expired at once; EntitySignal started active and lost components on sync(); ShakeEffect drifted; dartdoc crashed on engine.dart.

Deprecated

Removed in 3.0: Engine.getSystem, the legacy RenderingEngine renderable path, Engine.parallax and ParallaxSystem, onRenderBackground / onRenderOverlay, TagComponent.tag, HierarchySystem, Entity.generation, and the unused I* lifecycle interfaces (full list).

Known limitations

Joint anchors are not passed to the physics engine, the pure-Dart backend still pushes jointed bodies apart with collideConnected off, native queries skip bodies with collision mask 0, a stream's channel volume does not apply, and a playing sound's pitch, pan, speed and loop cannot change; they wait on just_physics_engine and just_audio_engine (details).

1.6.1 - 2026-08-02

Added

• Unified shape styling: ShapePaintStyle and ShapeGradient (linear, radial, sweep) now back fillStyle/strokeStyle on every shape component (CircleComponent, RectangleComponent, PolygonComponent, LineComponent, CapsuleComponent), replacing the old flat color property.
• Entity.removeComponentByType(Type type) and Entity.hasComponentByType(Type type) for runtime-type component access when the static type isn't known at the call site.

Changed

• ColliderDebuggerSystem relocated from core/debugger/ to core/ and exported via core.dart and systems.dart.
• just_physics_engine dependency upgraded to ^1.2.2.

1.6.0 - 2026-05-30

Added

• In-game developer terminal for commands and debugging, including GameWidget integration.
• Achievement subsystem with tracking, events, and provider abstraction.
• Authentication and leaderboard subsystems with platform provider support.
• Currency and inventory subsystems with event-driven updates.
• Ads subsystem with banner, interstitial, and rewarded support.
• Subtitle subsystem with cue controller and overlay widget.
• Checkpoint collision/respawn flow and checkpoint component support.
• Physics improvements: sensor support, collision event enhancements, and ColliderDebuggerSystem.

Changed

• Transform pipeline refactored for 3D-compatible data flow.
• Checkpoint respawn positions migrated to Vector3.
• Physics integration migrated to just_physics_engine and upgraded.
• Math utilities migrated to just_dart; obsolete math files removed.
• Achievement persistence moved from storage-backed flow to database-backed flow.
• GameWidget debugger integration simplified and legacy debugger path removed.
• Dependency metadata updated; pubspec_overrides.yaml added to .gitignore.

---

1.5.3 - 2026-04-19

Added

• Debugger Tooling — Added the new just_debugger integration to improve engine inspection, diagnostics, and runtime debugging workflows.

Changed

• Memory Management — Moved shared memory-related code out of just_game_engine into the dedicated just_memory package for clearer package boundaries and better reuse across the ecosystem.

---

1.5.2 - 2026-04-08

Added

• Shape Components — Five self-rendering ECS components that extend RenderableComponent and draw themselves each frame with no additional render system required.
  • CircleComponent — Circle centered on the entity's TransformComponent position. Properties: radius, color, filled, strokeWidth.
  • RectangleComponent — Axis-aligned rectangle with optional rounded corners. Properties: width, height, color, filled, strokeWidth, cornerRadius. Convenience size getter returns a Size object.
  • PolygonComponent — Convex or concave polygon defined by a list of local-space vertices. Properties: vertices, color, filled, strokeWidth.
  • LineComponent — Straight line segment in local space. Properties: start, end, color, strokeWidth, roundCaps. Convenience length getter for segment distance.
  • CapsuleComponent — Rectangle with two semicircular end caps (horizontal or vertical depending on aspect ratio). Properties: width, height, color, filled, strokeWidth. Computed capRadius getter (half of the shorter side).

---

1.5.1 - 2026-04-06

Fixed

• Update Archetype signature to use string keys and improve entity validation in addEntity method

---

1.5.0 - 2026-04-04

Added

• Post-Processing — PostProcessPass (full-screen FragmentShader, ordered chaining), ShaderComponent (per-entity or post-process mode), PostProcessSystem (priority 35).
• Sprite Atlas — SpriteAtlas, AtlasParser (auto-detects TexturePacker JSON Array/Hash/multi-page and Aseprite), AtlasAnimationClip, AtlasSpriteAnimation.
• Deterministic Effects — 11 tick-based effects (MoveEffect, ScaleEffect, RotateEffect, FadeEffect, ColorTintEffect, SequenceEffect, ParallelEffect, DelayEffect, RepeatEffect, ShakeEffect, PathEffect), EffectSystemECS (priority 65), JSON + binary serialization, EffectSnapshot for rollback.
• Localization — LocalizationManager with namespace support, fallback chain (fr_CA → fr → en), Signal<Locale>, ICU-lite {plural}/{select} via StringInterpolator, and Flutter widgets (LocalizationScope, LocalizedText, LocaleSelector).
• Narrative / Dialogue — Full Yarn Spinner 2.x parser and runtime (DialogueManager, YarnParser, DialogueRunner), DialogueLocalizer, ECS components (DialogueComponent, TriggerComponent, DialogueSystem), and UI widgets (DialogueBoxWidget, DialogueChoicesWidget).
• New ECS components: ShaderComponent, EffectComponent, ParallaxComponent, ParticleEmitterComponent, CameraFollowComponent.
• New ECS systems: PostProcessSystem, EffectSystemECS, ParticleSystemECS, CameraFollowSystem.

Changed

• Audio — Replaced flutter_soloud with just_audio_engine (^1.0.0); graceful degradation in headless/test environments; no user-facing API changes.
• SystemManager — Promoted to authoritative frame scheduler (registerUpdateTask, runUpdateCycle, schedulerStats); Engine.systemManager getter exposed publicly.
• Performance — Hot-path allocation audit: persistent Stopwatch fields, pre-allocated collision pair buffer, sub-frame render interpolation, LinkedHashSet render layers, archetype integer signatures, Zobrist query-cache keys, accumulator cap 5× → 3×, SpatialGrid hash entropy fix.
• Observability — Per-subsystem timing stats in GameWidget debug HUD; Quadtree caching in RenderingEngine; incremental SpatialGrid body tracking.
• Cache — CacheManager falls back to in-memory stores on plugin failure (isUsingMemoryFallback).
• CI — GitHub Actions (flutter analyze --fatal-infos + flutter test); @experimental on all networking stubs; analysis_options.yaml hardened; meta: ^1.9.0 dependency added.

---

1.4.2 - 2026-04-02

• Engine performance improved
• Engine stats updated

1.4.1 - 2026-03-25

Changed - Documentation & Examples

• README: Overhauled and streamlined — removed outdated sections and links to provide a cleaner, more up-to-date overview.
• Example: Consolidated the example suite into a single example.dart file covering the core engine setup. Removed the separate core_system_example.dart, ecs_example.dart, and input_test_example.dart files to reduce onboarding friction.

---

1.4.0 - 2026-03-21

Changed - Architecture & Performance

• Major change in architecture and imporved performance

Added - Parallax Background System

New first-class subsystem for multi-layer scrolling backgrounds, accessible via Engine.parallax.

• ParallaxLayer — Individual layer with depth-based scrolling.
  • scrollFactorX / scrollFactorY control camera-relative scroll speed (0.0 = fixed, 1.0 = camera speed).
  • velocityX / velocityY for continuous auto-scroll independent of camera movement.
  • scale, repeat, offset, opacity, and tint for full visual control.
  • ParallaxLayer.uniform() convenience constructor for equal X/Y scroll factors.
• ParallaxBackground — Ordered container of ParallaxLayer instances (index 0 = furthest back).
  • addLayer(), insertLayer(), removeLayer() for runtime layer management.
  • update(deltaTime) advances auto-scroll offsets; render(canvas, size) paints all layers back-to-front.
  • Per-layer camera-driven + auto-scroll + static offset compositing.
  • Tiling logic handles images smaller than the viewport with seamless horizontal/vertical wrapping.
• ParallaxSystem — Engine subsystem managing all registered backgrounds.
  • addBackground() / removeBackground() / clear() lifecycle methods.
  • update(deltaTime, cameraPosition) feeds camera position into every background each frame.
  • render(canvas, size) called via RenderingEngine.onRenderBackground in screen space (before camera transform).

Added - Virtual Joystick Widget

Reusable Flutter widget for touch-based directional input on mobile platforms.

• VirtualJoystick — StatefulWidget that handles pointer events and emits normalised direction vectors.
  • JoystickVariant.fixed — always-visible joystick anchored at a set position.
  • JoystickVariant.floating — appears at the touch-down point and follows the finger.
  • JoystickAxis constraint: both, horizontal, or vertical axis locking.
  • Configurable radius, showWhenInactive, inactiveOpacity, and anchorAlignment.
  • onDirectionChanged callback delivers a normalised Offset each frame for ECS integration.
  • Rendered via CustomPaint with base ring and thumb knob visuals.
• JoystickInputComponent — ECS component storing joystick state on an entity.
  • direction, basePosition, thumbPosition for runtime access.
  • layout (fixed / floating) and axis constraint properties.
  • hasInput, reset(), setDirectionFromDelta() helpers.
  • Automatically processed by InputSystem._updateJoystickComponents() alongside keyboard input.

---

1.3.0 - 2026-03-15

Added - Tiled Map ECS Integration

just_tiled is now a first-class runtime dependency of just_game_engine. The engine ships four new types that bridge parsed Tiled map data directly into the ECS world, covering rendering, collision, and object-to-entity spawning.

• TileMapLayerComponent — ECS component that attaches a TileLayer and its pre-compiled TileMapRenderer to a single entity. One entity per tile layer keeps the world free of per-tile entity bloat.
• TiledObjectComponent — ECS component for Tiled map objects. Exposes properties, type, and name directly on the entity for easy custom-logic dispatch.
• TiledMapFactory — Static factory that translates an entire TiledMap into ECS entities in one call.
  • Tile layers → one entity with TileMapLayerComponent + TransformComponent (respects layer offset).
  • Object groups → one entity per visible TiledObject with TransformComponent + TiledObjectComponent.
  • GroupLayer children are traversed recursively.
  • ComponentMapper callback maps any Tiled class name + custom properties to additional engine components (e.g. HealthComponent, EnemyAIComponent).
• TileMapRenderSystem — ECS System that GPU-batches all TileMapLayerComponent entities. Uses Camera.getVisibleBounds() for viewport frustum culling so only in-view tiles are processed. Runs at priority 100 so tile layers are painted before game entities.
• TiledCollisionSystem — ECS System that converts TMX object-group collision shapes into static PhysicsBody instances and registers them with PhysicsEngine.
  • Supports rectangle, polygon, and ellipse shapes (mapped to RectangleShape, PolygonShape, CircleShape).
  • Per-object restitution and friction read from Tiled custom properties.
  • Optional SpatialHashGrid<PhysicsBody> for O(1) proximity queries.
  • loadCollisions(TiledMap) / loadObjectGroupCollisions(ObjectGroup) / clearCollisions() lifecycle methods.

---

1.2.1 - 2026-03-15

Changed

• GameWidget: _GamePainter.paint() now also calls engine.world.render(canvas, size), so ECS entities registered with RenderSystem are drawn automatically alongside the classic rendering pipeline.

Added - Audio ECS Integration

Audio playback is now fully ECS-driven alongside the existing AudioEngine API.

• AudioSourceComponent — Persistent audio source on an entity. Properties: clipPath, volume, pan, loop, playOnAdd, channel (AudioChannel), is3d. When is3d is true, stereo pan is ignored and 3D position is derived from TransformComponent.
• AudioPlayComponent — Fire-and-forget one-shot playback trigger. AudioSystem plays the sound and removes the component automatically.
• AudioListenerComponent — Marks an entity (typically the camera or player) as the SoLoud 3D listener. AudioSystem forwards the entity's TransformComponent position to the native listener each frame.
• AudioSystem — ECS System that drives all audio ECS components. Runs at priority -10 (after transforms) to ensure 3D positions are up to date before the listener and source positions are sent to SoLoud.

Fixed

• Example: Simplified example/example.dart to a minimal renderer setup for easier onboarding.

---

1.2.0 - 2026-03-12

Added - Ray Casting & Ray Tracing

• Ray — 2-D ray descriptor with origin, normalised direction, and maximum travel distance.
  • Ray.fromPoints() convenience constructor for aiming between two world positions.
  • at(t) helper returns the world-space point at a given distance along the ray.
• RaycastColliderComponent — ECS component that marks an entity as hittable by rays.
  • Configurable radius, semantic tag for filtering, isBlocker flag, and isReflective / reflectivity properties for multi-bounce tracing.
• RaycastHit — intersection result containing the hit entity, world-space point, distance, and outward surface normal.
• RaycastSystem — query-only ECS system for ray-vs-collider tests.
  • castRay() returns the closest hit; castRayAll() returns all hits sorted nearest-first.
  • hasLineOfSight() performs a line-of-sight / LOS check between two points.
• RayTracer — multi-bounce ray tracing against reflective surfaces.
  • Configurable maxBounces and minReflectivity thresholds.
  • trace() returns a RayTrace containing every RayTraceSegment (path segment + optional hit).

Added - Ray Renderable

• RayRenderable — a Renderable that draws a glowing beam / laser / bullet trail in world space.
  • Two-layer visual: a sharp core line and a wider blurred glow halo for a neon/laser effect.
  • Automatic fade-out over a configurable lifetime; isExpired flag for easy cleanup.
  • Customisable color, width, glowWidthMultiplier, and glowBlurSigma.

---

1.1.2 - 2026-03-08

Changed

• Audio Engine: Replaced audioplayers with flutter_soloud (^3.5.0) as the audio backend.
  • SoLoud is a low-latency, C++-based audio engine purpose-built for games.
  • Removed the fixed-size AudioPlayer pool; SoLoud handles unlimited concurrent voices natively.
  • AudioClip now holds an AudioSource + SoundHandle instead of an AudioPlayer.
  • AudioEngine.initialize() is now async and calls SoLoud.instance.init(); the engine properly awaits it during startup so audio is guaranteed ready before any play calls.
  • Added isInitialized guard in initialize() to be safe against duplicate init (e.g. hot restart).
  • playSfx() and playMusic() return early with a debug message if called before initialization.
  • Music fade-in/fade-out now delegates to SoLoud.instance.fadeVolume() instead of a manual step loop.
  • dispose() calls SoLoud.instance.deinit() to fully shut down the engine.

1.1.1 - 2026-03-07

• Homepage URL updated in pubspec.yaml.
• Added reactive ECS components and signals for improved state management.

1.1.0 - 2026-03-01

Added - Advanced Physics Engine

• Rigid Body Dynamics
  • Upgraded physics integration to Semi-Implicit Euler.
  • Added new dynamic properties to PhysicsBody: angularVelocity, angle, torque, inertia, and friction.
  • Added support for static bodies by setting mass: 0.0.
• Advanced Collision Shapes
  • Implemented CollisionShape hierarchy replacing simple radius.
  • Added CircleShape, RectangleShape, and PolygonShape.
  • Implemented Separating Axis Theorem (SAT) for true polygon-polygon and circle-polygon collision detection.
• Impulse-Based Resolution
  • Added rigorous impulse delivery resolving velocity along collision normals using inverse mass scaling.
  • Included Coulomb friction handling for sliding objects.
• Broad-Phase Optimization
  • Implemented $O(n)$ SpatialGrid broad-phase for massive performance gains in dense scenes.
  • Added Object Sleeping: resting bodies are excluded from integration until awoken, saving CPU cycles.
• Physics Caching
  • Integrated CacheManager utilizing just_storage and just_database.
  • Added cachePolygonShape and getCachedPolygonShape routines to persist heavy math computations across sessions.

---

1.0.1 - 2026-02-24

Fixed

• Audio Engine
  • Fixed AudioClip.play() crash caused by AudioCache double-prefixing the asset path (assets/assets/...) when the caller passed a path already starting with assets/. The path is now stripped of the assets/ prefix before being passed to AssetSource.

Changed

• License
  • Changed project license from Apache 2.0 to BSD-3-Clause.

---

1.0.0 - 2026-02-16

Added - Core Systems

• Engine Core

  • Main Engine singleton class for orchestrating all subsystems
  • GameLoop with fixed timestep (60 UPS) and variable rendering
  • TimeManager for delta time tracking and FPS calculation
  • SystemManager for coordinating subsystems
  • Full lifecycle management (initialize, start, pause, resume, stop, dispose)
  • Engine state machine with 6 states (uninitialized, initializing, initialized, running, paused, error)

• Rendering Engine

  • Canvas-based 2D rendering system
  • Camera class with pan, zoom, rotation, and lookAt functionality
  • Layer-based rendering with Z-order sorting
  • Built-in renderables: CircleRenderable, RectangleRenderable, LineRenderable, TextRenderable, CustomRenderable
  • GameWidget for Flutter integration with CustomPainter
  • Debug mode with bounding boxes and coordinate grids
  • Background color support
  • FPS display overlay

Added - Advanced Features

• Sprite System

  • Sprite class for image rendering with source rectangles
  • SpriteSheet for managing sprite atlases
  • NineSliceSprite for scalable UI elements
  • Horizontal and vertical flipping support
  • Static fromAsset method for easy loading

• Animation System

  • Base Animation class with play, pause, stop, reset controls
  • SpriteAnimation for frame-based sprite animations:
    • Automatic frame cycling based on normalized time
    • fromSpriteSheet() factory method for easy creation
    • Support for variable frame counts (any number of frames)
    • Configurable frame dimensions (width/height)
    • Manual frame list support via List<Rect> frames parameter
  • Generic TweenAnimation<T> with custom lerp functions
  • Property tweens: PositionTween, RotationTween, ScaleTween, OpacityTween, ColorTween
  • AnimationSequence for chaining animations
  • AnimationGroup for parallel animations
  • Easings class with 15+ easing functions:
    • Linear
    • Quadratic (in, out, in-out)
    • Cubic (in, out, in-out)
    • Quartic (in, out, in-out)
    • Sine (in, out, in-out)
    • Exponential (in, out, in-out)
    • Elastic (in, out, in-out)
    • Bounce (in, out, in-out)
  • Loop and ping-pong support
  • Speed control (0.1x - 5.0x) with dynamic adjustment
  • Normalized time (0.0 - 1.0) for progress tracking
  • Completion callbacks

• Particle Effects

  • ParticleEmitter with configurable emission rate and lifetime
  • Individual Particle class with full lifecycle
  • Size gradient support (start → end)
  • Color gradient support with smooth transitions
  • Gravity and velocity simulation
  • Multiple particle shapes: circle, square, star
  • Built-in effect presets:
    • Explosion (burst of orange/yellow particles)
    • Fire (rising orange flames with flicker)
    • Smoke (upward gray particles with fade)
    • Sparkle (twinkling yellow/white particles)
    • Rain (falling blue droplets)
    • Snow (gentle falling white flakes)
  • Custom particle system creation

• Physics Engine

  • PhysicsBody rigid body class
  • Circular collision detection
  • Elastic collision resolution with restitution
  • Mass, velocity, drag, and radius properties
  • Gravity simulation (configurable)
  • Debug rendering with:
    • Body visualization (green = active, red = inactive)
    • Velocity vector arrows
    • Collision boundary circles
  • Broad-phase and narrow-phase collision optimization

• Scene Graph

  • Hierarchical SceneNode structure
  • Parent-child transform relationships
  • Local and world-space coordinate systems
  • Transform propagation (position, rotation, scale)
  • SceneEditor for scene management
  • Scene container class
  • Node finding by name (recursive search)
  • Active/inactive state per node
  • Depth calculation
  • Custom update callbacks per node
  • Renderable attachment to nodes

• Entity-Component System (ECS)

  • World class for managing all entities and systems
  • Entity class representing game objects with components
  • Component base class for pure data containers
  • System base class for processing logic
  • Entity lifecycle management (create, destroy, query)
  • Component filtering and queries
  • System priority and ordering
  • Entity statistics and debugging
  • 13 built-in components:
    • TransformComponent - Position, rotation, scale with transform methods
    • VelocityComponent - Velocity vector with max speed and angle utilities
    • RenderableComponent - Links to renderable objects with sync options
    • PhysicsBodyComponent - Radius, mass, restitution, drag, collision layers
    • TagComponent - Simple string tagging for entity identification
    • LifetimeComponent - Time-based entity expiration
    • HealthComponent - HP system with damage, heal, and invulnerability
    • ParentComponent - Parent reference with local offset and rotation
    • ChildrenComponent - Child entity list management
    • InputComponent - Movement direction and button state
    • AnimationStateComponent - Current animation state tracking
    • SpriteComponent - Sprite path, frame, flip flags, and tint color
  • 9 built-in systems:
    • MovementSystem - Applies velocity to transform with max speed clamping
    • RenderSystem - Renders entities with transform sync
    • LifetimeSystem - Updates lifetime and destroys expired entities
    • PhysicsSystem - Full physics with gravity, drag, collision detection/resolution, layer-based filtering
    • HierarchySystem - Propagates parent transforms to children
    • HealthSystem - Health regeneration and death handling
    • AnimationSystemECS - Animation time updates
    • BoundarySystem - World boundary enforcement with 4 behaviors (clamp, bounce, wrap, destroy)
  • Data-oriented architecture for performance
  • Composition over inheritance design
  • Query system for finding entities by components
  • Example implementation in ecs_example.dart

Added - Supporting Systems

• Input Management

  • InputManager main coordinator with subsystem access
  • KeyboardInput with key press/hold/release detection
  • Key state tracking with previous frame comparison
  • Horizontal and vertical axis support for WASD/Arrow keys
  • MouseInput with position, button, and scroll tracking
  • Mouse delta and scroll delta calculation
  • Support for left, right, and middle mouse buttons
  • Screen-to-world coordinate conversion support
  • TouchInput with multi-touch support
  • Touch point tracking with pressure and size
  • Touch start/end events per frame
  • ControllerInput with gamepad support
  • Analog stick support (left/right sticks)
  • Trigger and button detection
  • Configurable dead zone for analog inputs
  • Event callback system for custom input handling
  • Automatic integration with GameWidget via Focus and Listener
  • Input state updates each frame in game loop

• Audio Engine

  • AudioEngine main coordinator with multi-channel mixing
  • AudioClip wrapper for individual audio playback control
  • SoundEffectManager for managing sound effects
  • MusicManager for background music with fade effects
  • AudioMixer for volume and mute control
  • 5 audio channels: Master, Music, SFX, Voice, Ambient
  • Per-channel volume control with independent mute/unmute
  • Unlimited concurrent SFX via SoLoud's native voice management
  • Automatic cleanup of finished audio clips
  • Music fade in/out support (configurable duration)
  • Looping support for music and ambient sounds
  • Built on audioplayers package (^6.1.0) (replaced by flutter_soloud in v1.1.2)
  • Supports MP3, WAV, OGG, FLAC audio formats
  • State tracking (stopped, playing, paused)
  • Integration methods: playSfx(), playMusic(), stopMusic(), setMasterVolume()

• Asset Management

  • AssetManager for loading and caching game resources
  • Asset base class with load/unload lifecycle
  • ImageAsset for loading PNG/JPG images with ui.Image
  • AudioAsset for loading audio files as binary data
  • TextAsset for loading plain text files
  • JsonAsset for loading and parsing JSON configuration
  • BinaryAsset for loading raw binary data
  • AssetBundle for grouping related assets
  • Automatic caching system to prevent duplicate loads
  • Memory usage tracking per asset (in bytes)
  • Cache statistics: total assets, images, audio, text, JSON, binary counts
  • Total memory usage calculation
  • Async loading with futures
  • Integration with Flutter's rootBundle
  • Support for atlas/sprite sheet metadata
  • Unload functionality to free memory
  • Type-safe asset retrieval methods

• Networking (Placeholder)

  • Structure for multiplayer support
  • Client-server communication

Examples

• core_system_example.dart - Complete engine setup example
• ecs_example.dart - Entity-Component System with physics and collisions
• input_test_example.dart - Comprehensive input system demo with keyboard, mouse, and touch

Technical Details

• Minimum Flutter SDK: 3.11.0
• Minimum Dart SDK: 3.0.0
• External dependencies:
  • audioplayers: ^6.1.0 (for Audio Engine) (replaced by flutter_soloud in v1.1.2)
• Singleton pattern for Engine
• Observer pattern for lifecycle events
• Component-based architecture
• Fixed timestep game loop (60 UPS)
• Variable rendering for smooth visuals
• Efficient collision detection with spatial awareness

Performance

• Maintains 60 FPS with 20+ objects
• Handles 100+ particles simultaneously
• Real-time collision detection for multiple bodies
• Optimized rendering pipeline
• Low memory footprint

---

Version History

• 1.5.3 - Moved memory code to just_memory and added the new debugger tool
• 1.5.2 - Shape Components: CircleComponent, RectangleComponent, PolygonComponent, LineComponent, CapsuleComponent (all self-rendering, extend RenderableComponent)
• 1.5.1 - Bug fixes: Update Archetype signature to use string keys and improve entity validation in addEntity method
• 1.5.0 - Post-Processing shaders, Sprite Atlas, Deterministic Effects, Localization, Narrative/Dialogue, audio backend swap (just_audio_engine), SystemManager frame scheduler, hot-path allocation audit, runtime observability, CI/CD
• 1.4.2 - Performance improvements
• 1.4.1 - Documentation overhaul and example consolidation
• 1.4.0 - Parallax Background System, Virtual Joystick Widget, and showcase app improvements
• 1.3.0 - Tiled Map ECS integration (TiledMapFactory, TileMapRenderSystem, TiledCollisionSystem) and Audio ECS integration (AudioSourceComponent, AudioSystem)
• 1.2.1 - GameWidget ECS rendering integration and example cleanup
• 1.2.0 - Ray Casting, Ray Tracing, and Ray Renderable systems
• 1.1.0 - Complete Physics Engine overhaul (Rigid Body Dynamics, SAT Shapes, Spatial Grid, and Impulse Resolution)
• 1.0.1 - Bug fix for audio asset path and license update to BSD-3-Clause
• 1.0.0 - Full production release with all core features