Set up and debug a Phaser 4 game: the Game config, the Scene lifecycle (init/preload/create/update), the asset loader, cameras, and cross-scene communication. Use when building or debugging a Phaser game — when the user mentions Phaser, Phaser.Game, Phaser.Scene, preload/create/update, this.load, th

Phaser 4 Core Set up the foundation of a Phaser game: the Game config, the Scene lifecycle, asset loading, cameras, and passing data between scenes. Targets Phaser 4.2 for new projects; keep an existing Phaser 3.90 project on its pinned major unless the user explicitly asks for a migration. When to use Use when starting a Phaser game, wiring the Phaser.Game config, structuring Scene s, loading assets in preload , or fixing scene transitions and shared state. Use when the project has phaser in package.json or import Phaser from 'phaser' , and code uses preload() / create() / update() . When not to use: movement, velocity, colliders, gravity, or overlap → use phaser arcade physics . Complex rigid body simulation uses Matter physics (a separate concern). For cross engine save/load patterns use save systems . Core workflow 1. Detect the installed major first. Read package.json and the lockfile. Use Phaser 4.2 for new work; do not silently rewrite a Phaser 3 project as Phaser 4. 2. Create the game from a config. new Phaser.Game(config) with type: Phaser.AUTO (WebGL with Canvas fallback), a width / height , and a scene array. The first scene (and any with active: true ) starts automatically. 3. Model each screen as a Scene . Subclass Phaser.Scene , pass a unique key to super , and implement the lifecycle: init(data) → preload() → create(data) → update(time, delta) . 4. Load assets in preload , use them in create . Queued assets are not available until create . The loader is per scene; the cache it fills is global. 5. Reset per run state in init() , not the constructor. A scene instance is reused across restarts, so constructor set fields keep stale values. 6. Move between screens with this.scene.start/launch/switch/sleep/wake . Share data through this.registry (global) or a sibling scene's event emitter. 7. Run and observe. Serve the page, open it, and confirm assets load (watch the Network tab and console) and scenes switch as expected before assuming success. Patterns 1. Game config + boot (ES module) 2. A Scene with the full lifecycle 3. Cross scene data + events 4. Scene transitions (pick the right verb) 5. A camera that follows the player Pitfalls A key works once, then stays down (or Left + Right cancel out) → in Phaser 4.2.1, a keyup cancelled before the keyboard manager receives it is ignored because event.defaultPrevented is set. Inspect host page listeners and browser extensions before changing movement code. Read the keyboard diagnosis and capture phase fallback contract in references/scene flow.md . Assets are undefined in create / update → you forgot to queue them in preload , or used the wrong key. The loader runs between preload and create . State leaks across a restart → you set fields in the constructor. The Scene instance is reused; reset run state in init() and clear arrays on shutdown . this.scene.start vs this.scene.launch → start stops the calling scene; launch runs the target alongside it. Using start for a HUD hides the game. HUD loses its state or draws behind the game → launch (and run ) on a scene that is already running shuts it down and starts it again; launch the HUD once, or guard with if (!this.scene.isActive('hud')) . Scenes draw in scene list order, so a HUD listed before the gameplay scene renders underneath it until you call this.scene.bringToTop('hud') . Scene state read right after start / launch is stale → scene operations are queued and run at the start of the next game step, not synchronously. this is wrong in a callback → arrow functions keep the Scene's this ; plain function callbacks need a context argument or .bind(this) . Phaser 2 tutorials don't work → "States" were renamed to "Scenes" in Phaser 3, and each Scene owns its own systems (input, cameras, tweens) rather than a global Game World. Phaser 3 custom pipelines fail in Phaser 4 → Phaser 4 rebuilt the renderer and replaced the old FX/pipeline extension points. Migrate custom shaders and renderer plugins against the Phaser 4 guide; do not mechanically copy internal renderer code. A Phaser 3 snippet runs but looks wrong in Phaser 4 → common renames: preFX / postFX and BitmapMask became filters ( obj.enableFilters() then obj.filters.internal / .external ); setPipeline('Light2D') became setLighting(true) ; setTintFill(c) only logs an error, so use setTint(c).setTintMode(Phaser.TintModes.FILL) ; Phaser.Math.TAU is now 2π (use Phaser.Math.PI OVER 2 where v3 code meant π/2); Geom.Point is gone (use Phaser.Math.Vector2 ). Canvas rendering still works but is deprecated. Pixel art is blurry or shimmers while moving → set pixelArt: true in the game config. It turns off antialiasing and turns on roundPixels , which defaults to false in Phaser 4. Nothing renders / black screen → confirm the canvas mounted, width / height are set, and a scene actually started (check game.scene.dump() output). Two canvases (two games running) after a hot reload or a React/Vue remount → a second new Phaser.Game ran while the first was still alive. Keep one instance and call game.destroy(true) when the host component unmounts; the teardown finishes on the next frame. Leave noReturn false, or no new game can start on the page. References For the full scene state machine (pause/resume vs sleep/wake vs stop/start, the restart state bug, removing/replacing scenes, and stuck keyboard input), read references/scene flow.md . Related skills phaser arcade physics — velocity, gravity, colliders, overlap, and groups. input systems — rebindable, multi device input architecture (engine agnostic). pixijs rendering / threejs scene setup — other browser rendering stacks. platformer / puzzle — genre templates that compose Phaser skills.

phaser-core