Phaser 4 Animations and Tweens

Phaser 4 has two distinct animation systems: frame-based sprite animations (flip through frames in a texture atlas or spritesheet) and tweens (interpolate numeric properties over time). Use both together for polished game feel.

Creating Spritesheet Animations

A spritesheet packs multiple frames into a single image in a regular grid. Define animations in AnimationManager using frame indices.

// preload()
preload(): void {
  this.load.spritesheet('player', 'assets/player.png', {
    frameWidth: 48,
    frameHeight: 48,
  });
}

// create() — or PreloaderScene.create() for global animations (see below)
create(): void {
  this.anims.create({
    key:       'player-idle',
    frames:    this.anims.generateFrameNumbers('player', { start: 0, end: 3 }),
    frameRate: 8,
    repeat:    -1,           // -1 = loop forever
  });

  this.anims.create({
    key:       'player-walk',
    frames:    this.anims.generateFrameNumbers('player', { start: 4, end: 11 }),
    frameRate: 12,
    repeat:    -1,
  });

  this.anims.create({
    key:       'player-jump',
    frames:    this.anims.generateFrameNumbers('player', { start: 12, end: 15 }),
    frameRate: 10,
    repeat:    0,            // 0 = play once
  });

  this.anims.create({
    key:       'player-attack',
    frames:    this.anims.generateFrameNumbers('player', { start: 16, end: 23 }),
    frameRate: 16,
    repeat:    0,
  });
}

generateFrameNumbers Options

this.anims.generateFrameNumbers('texture', {
  start:  0,          // first frame index
  end:    7,          // last frame index (inclusive)
  first:  0,          // override which frame plays first
  frames: [0, 2, 4],  // manual frame list (use instead of start/end)
});

Atlas-Based Animations

Texture atlases store frames with named keys rather than grid positions. Use generateFrameNames for these:

// preload()
this.load.atlas('hero', 'assets/hero.png', 'assets/hero.json');

// create()
this.anims.create({
  key:       'hero-run',
  frames:    this.anims.generateFrameNames('hero', {
    prefix:  'run_',    // frame names are run_01, run_02, ...
    start:   1,
    end:     8,
    zeroPad: 2,         // zero-pad the number to 2 digits
    suffix:  '',        // optional suffix after the number
  }),
  frameRate: 12,
  repeat:    -1,
});

// Manual frame list from atlas
this.anims.create({
  key:    'hero-die',
  frames: [
    { key: 'hero', frame: 'die_01' },
    { key: 'hero', frame: 'die_02' },
    { key: 'hero', frame: 'die_03' },
  ],
  frameRate: 8,
  repeat:    0,
});

Where to Define Animations

Define animations in PreloaderScene.create() — not in each individual scene. Animations registered on the global AnimationManager are available in every scene without re-registering:

// src/scenes/PreloaderScene.ts
export class PreloaderScene extends Phaser.Scene {
  preload(): void {
    this.load.spritesheet('player', 'assets/player.png', { frameWidth: 48, frameHeight: 48 });
    this.load.atlas('enemies', 'assets/enemies.png', 'assets/enemies.json');
  }

  create(): void {
    // All anims defined here are available in GameScene, UIScene, etc.
    this.anims.create({ key: 'player-idle', /* ... */ });
    this.anims.create({ key: 'player-walk', /* ... */ });
    this.anims.create({ key: 'enemy-walk',  /* ... */ });

    this.scene.start('GameScene');
  }
}

If an animation only makes sense in a single scene (a cutscene animation, for example), define it in that scene's create().

Playing Animations

// Basic play
sprite.play('player-walk');

// Play but don't restart if already playing this animation
sprite.play('player-walk', true);    // ignoreIfPlaying = true

// Play starting from a specific frame
sprite.playFromFrame('player-walk', 3);

// Stop on a specific frame number
sprite.stopOnFrame(this.anims.get('player-attack').frames[7]);

// Reverse playback
sprite.playReverse('player-walk');

// Check state
sprite.anims.isPlaying;                    // boolean
sprite.anims.currentAnim?.key;             // string | undefined
sprite.anims.currentFrame?.index;          // current frame index

Animation Events

Listen for animation lifecycle events on the sprite (not the AnimationManager):

// Fires when any animation completes on this sprite
sprite.on(Phaser.Animations.Events.ANIMATION_COMPLETE, (anim, frame, gameObject) => {
  console.log('animation complete:', anim.key);
});

// Fires when a SPECIFIC animation completes (preferred — avoids key checks)
sprite.on(
  Phaser.Animations.Events.ANIMATION_COMPLETE_KEY + 'player-attack',
  (anim, frame, gameObject) => {
    this.player.returnToIdle();
  }
);

// Other events
sprite.on(Phaser.Animations.Events.ANIMATION_START,   cb);  // animation started
sprite.on(Phaser.Animations.Events.ANIMATION_REPEAT,  cb);  // loop restarted
sprite.on(Phaser.Animations.Events.ANIMATION_RESTART, cb);  // play() called while already playing
sprite.on(Phaser.Animations.Events.ANIMATION_STOP,    cb);  // stop() called
sprite.on(Phaser.Animations.Events.ANIMATION_UPDATE,  cb);  // every frame change

Always remove listeners when the sprite is destroyed to prevent memory leaks:

sprite.on(Phaser.Animations.Events.ANIMATION_COMPLETE, this.onAnimComplete, this);
// In shutdown():
sprite.off(Phaser.Animations.Events.ANIMATION_COMPLETE, this.onAnimComplete, this);

Animation Chaining

Play a sequence of animations one after another:

// Chain via array — plays 'attack', then 'idle' automatically
sprite.chain(['player-attack', 'player-idle']);
sprite.play('player-attack');

// Chain via ANIMATION_COMPLETE event
sprite.play('player-jump');
sprite.once(
  Phaser.Animations.Events.ANIMATION_COMPLETE_KEY + 'player-jump',
  () => sprite.play('player-fall')
);

Character State Machine Pattern

For characters with idle/walk/jump/attack states, use an explicit state machine in update(). This prevents impossible state transitions and makes animation logic readable.

type CharState = 'idle' | 'walk' | 'jump' | 'attack' | 'hurt';

export class Player extends Phaser.Physics.Arcade.Sprite {
  private state: CharState = 'idle';

  setState(newState: CharState): void {
    if (this.state === newState) return;
    this.state = newState;
    switch (newState) {
      case 'idle':   this.play('player-idle',   true); break;
      case 'walk':   this.play('player-walk',   true); break;
      case 'jump':   this.play('player-jump',   true); break;
      case 'attack': this.play('player-attack', true); break;
      case 'hurt':
        this.play('player-hurt', true);
        this.once(
          Phaser.Animations.Events.ANIMATION_COMPLETE_KEY + 'player-hurt',
          () => this.setState('idle')
        );
        break;
    }
  }

  update(cursors: Phaser.Types.Input.Keyboard.CursorKeys): void {
    const body = this.body as Phaser.Physics.Arcade.Body;

    if (this.state === 'attack' || this.state === 'hurt') return;  // locked states

    if (!body.blocked.down) {
      this.setState('jump');
    } else if (cursors.left.isDown || cursors.right.isDown) {
      this.setState('walk');
    } else {
      this.setState('idle');
    }

    if (Phaser.Input.Keyboard.JustDown(cursors.space)) {
      this.setState('attack');
      this.once(
        Phaser.Animations.Events.ANIMATION_COMPLETE_KEY + 'player-attack',
        () => this.setState('idle')
      );
    }
  }
}

Forced Animations: Cinematic Mode

When a one-shot animation (boss intro, death sequence, dungeon entry) plays for one frame then reverts to idle, the cause is always the entity's update() running its state-machine logic one tick after your forced play() call and overwriting it.

Fix — add a cinematicMode flag as the very first guard in update():

export class Player extends Phaser.Physics.Arcade.Sprite {
  private state: CharState = 'idle';
  private cinematicMode = false;

  setCinematicMode(active: boolean, forcedAnimKey?: string): void {
    this.cinematicMode = active;
    if (active && forcedAnimKey) {
      this.anims.stop();          // always stop before play on a state switch
      this.play(forcedAnimKey, true);
      this.once(
        Phaser.Animations.Events.ANIMATION_COMPLETE_KEY + forcedAnimKey,
        () => { this.cinematicMode = false; }
      );
    }
  }

  update(cursors: Phaser.Types.Input.Keyboard.CursorKeys): void {
    if (this.cinematicMode) return;  // MUST be first line — blocks state logic
    // ... rest of state machine
  }
}

Clear cinematicMode in the ANIMATIONCOMPLETEKEY handler, not synchronously after play() — the completion event fires after the last frame renders, and update() may run before your handler. Clear it synchronously and your forced animation exits one frame early.

See references/state-machine-patterns.md for the full canonical implementation, worked dungeon-entry example, and the ANIMATION_COMPLETE timing fix.

State Transition Completeness

Adding a new animation state without auditing all other states' transition lists is a silent bug — no error is thrown; the state machine simply fails to reach the new state or gets stuck in the wrong one.

When adding any new state (e.g. 'dodge', 'interact'):

1. Add it to the CharState union type.
2. Add a case for it in setState().
3. Update every other state's "what can interrupt me" logic to include or exclude the new state as appropriate.

The transition table in references/state-machine-patterns.md makes missing transitions obvious on read.

Stopping and Pausing Animations

sprite.stop();            // stop and stay on current frame
sprite.anims.pause();     // pause on current frame (resumable)
sprite.anims.resume();    // resume paused animation
sprite.anims.restart();   // restart from frame 0

Tweens

Tweens interpolate any numeric property on any object over time. They are Phaser's primary tool for UI animations, cutscenes, and visual feedback.

this.tweens.add({
  targets:    sprite,       // one object, an array, or a group
  x:          400,          // tween x to 400
  y:          300,
  alpha:      1,
  duration:   800,          // milliseconds
  ease:       'Quad.Out',   // easing function
  delay:      0,            // ms before starting
  repeat:     0,            // 0 = once; -1 = infinite
  yoyo:       false,        // reverse back to start after completing
  hold:       0,            // ms to hold at end before yoyo
  onStart:    () => {},     // fires when tween starts
  onUpdate:   () => {},     // fires every frame
  onComplete: () => {},     // fires on completion
});

Common Tween Patterns

Fade In

sprite.setAlpha(0);
this.tweens.add({ targets: sprite, alpha: 1, duration: 400, ease: 'Linear' });

Fade Out and Destroy

this.tweens.add({
  targets:    sprite,
  alpha:      0,
  duration:   300,
  ease:       'Linear',
  onComplete: () => sprite.destroy(),
});

Scale Pulse (hit feedback, collectible)

this.tweens.add({
  targets:  sprite,
  scaleX:   1.3,
  scaleY:   1.3,
  duration: 80,
  ease:     'Quad.Out',
  yoyo:     true,
});

Slide In From Edge

// Slide in from left
sprite.setX(-100);
this.tweens.add({
  targets:  sprite,
  x:        400,
  duration: 500,
  ease:     'Back.Out',
});

Bounce Landing

sprite.setY(targetY - 100);
this.tweens.add({
  targets:  sprite,
  y:        targetY,
  duration: 600,
  ease:     'Bounce.Out',
});

Tween Easing Functions

See references/easing-reference.md for the complete guide with all easing functions and use cases.

Quick reference:

• 'Linear' — constant speed; mechanical, UI bars
• 'Quad.Out' — fast start, decelerates; most natural movement
• 'Quad.In' — accelerates; falling objects, winding up
• 'Quad.InOut' — symmetric ease; camera moves
• 'Back.Out' — overshoots target then settles; UI popups, dialog slides
• 'Bounce.Out' — bounces at destination; objects hitting ground
• 'Elastic.Out' — spring oscillation; comic, bouncy UI

Tween Timelines

Sequence multiple tweens without nesting onComplete callbacks:

this.tweens.timeline({
  tweens: [
    {
      targets:  panel,
      alpha:    1,
      duration: 200,
    },
    {
      targets:  panel,
      y:        300,
      duration: 400,
      ease:     'Back.Out',
    },
    {
      targets:  title,
      alpha:    1,
      duration: 300,
      offset:   '-=100',   // start 100ms before previous tween ends (overlap)
    },
    {
      targets:  button,
      alpha:    1,
      duration: 200,
      // no offset = starts after previous completes
    },
  ],
});

offset controls timing relative to the previous tween:

• '-=200' — overlap by 200ms
• '+=200' — add 200ms gap
• absolute number — start at that ms from timeline start

Particle Animations (Brief)

For burst effects (explosions, pickups, impacts), use the built-in particle system:

// One-shot burst
this.add.particles(x, y, 'spark', {
  speed:     { min: 50, max: 200 },
  angle:     { min: 0, max: 360 },
  scale:     { start: 1, end: 0 },
  lifespan:  600,
  quantity:  12,
  emitting:  false,         // don't start automatically
}).explode(12);             // emit 12 particles immediately then stop

// Persistent emitter (fire, rain)
const emitter = this.add.particles(x, y, 'flame', {
  speed:    30,
  lifespan: 1200,
  scale:    { start: 0.8, end: 0 },
  alpha:    { start: 1, end: 0 },
  frequency: 80,            // ms between emissions
});
// Stop later:
emitter.stop();

Additional Resources

Reference Files

• references/animation-api.md — Complete AnimationManager, AnimationConfig, Animation events, TweenManager, and Timeline API reference
• references/easing-reference.md — All built-in easing functions with descriptions, use cases, and code examples
• references/state-machine-patterns.md — State-machine discipline for characters: cinematicMode flag, canonical state list, transition table, the stop()/play() ordering rule, and ANIMATION_COMPLETE timing. Read when building any character with more than idle+walk, or when forced animations play for one frame and revert.