Phaser Arcade Physics Agent Skill

Phaser 3 Arcade Physics

Add movement and collision to a Phaser 3 game with the lightweight **Arcade

Physics engine (AABB rectangles and circles only). Targets Phaser 3.90**.

When to use

• Use for top-down or platformer movement, velocity/acceleration/gravity, bouncing,

world bounds, and collision/overlap resolution between sprites, groups, and tiles.

• Use when the scene enables physics: { default: 'arcade' } and code calls

this.physics.add.*, body.setVelocity, or this.physics.add.collider.

When *not* to use: the Game config, scene structure, asset loading, or

cameras → use phaser-core. Hinges, springs, complex polygons, or stacking

rigid bodies → use Matter physics (a different engine; Arcade and Matter bodies

do not interact). For engine-agnostic feel tuning see physics-tuning.

Core workflow

• Enable the world. Set `physics: { default: 'arcade', arcade: { gravity:

{...}, debug: true } } in the game or scene config. Turn debug` on while

building to see body outlines and velocity vectors.

• Give a sprite a body. Create it with this.physics.add.sprite(...) (dynamic)

or this.physics.add.staticImage(...) (static), or attach to an existing object

with this.physics.add.existing(obj).

• Drive it through the body, not by setting x/y. Use setVelocity,

setAcceleration, gravity, setBounce, and setCollideWorldBounds. The engine

integrates position from velocity each step (already frame-rate independent).

• Resolve interactions. this.physics.add.collider(a, b) separates bodies;

this.physics.add.overlap(a, b, cb) detects without separating (pickups,

triggers). Pass a callback to react.

• Group many objects. Use this.physics.add.group() (dynamic) or

staticGroup() (platforms) so one collider call handles all members.

• Check ground contact with body.onFloor() / body.blocked.down before

jumping. Run with debug: true and confirm bodies, contacts, and bounds.

Patterns

1. Enable Arcade Physics (game config)

const config = {
  type: Phaser.AUTO,
  width: 800, height: 600,
  physics: {
    default: 'arcade',
    arcade: {
      gravity: { x: 0, y: 600 },  // top-down? use { x: 0, y: 0 }
      debug: false                // true to draw bodies + velocity while building
    }
  },
  scene: [PlayScene]
};
new Phaser.Game(config);

2. Top-down movement (velocity from input)

create() {
  this.player = this.physics.add.sprite(400, 300, 'player');
  this.player.setCollideWorldBounds(true);
  this.cursors = this.input.keyboard.createCursorKeys();
}

update() {
  const speed = 220;
  const body = this.player.body;
  body.setVelocity(0);                              // reset each frame
  if (this.cursors.left.isDown)  body.setVelocityX(-speed);
  if (this.cursors.right.isDown) body.setVelocityX(speed);
  if (this.cursors.up.isDown)    body.setVelocityY(-speed);
  if (this.cursors.down.isDown)  body.setVelocityY(speed);
  body.velocity.normalize().scale(speed);           // keep diagonals same speed
}

3. Platformer jump (gravity + ground check)

create() {
  this.player = this.physics.add.sprite(100, 450, 'player');
  this.player.setCollideWorldBounds(true);

  // Static platforms: one body each, never moved by collisions.
  this.platforms = this.physics.add.staticGroup();
  this.platforms.create(400, 568, 'ground');
  this.physics.add.collider(this.player, this.platforms);

  this.cursors = this.input.keyboard.createCursorKeys();
}

update() {
  const onGround = this.player.body.blocked.down; // or this.player.body.onFloor()
  if (this.cursors.left.isDown)  this.player.setVelocityX(-160);
  else if (this.cursors.right.isDown) this.player.setVelocityX(160);
  else this.player.setVelocityX(0);

  if (this.cursors.up.isDown && onGround) this.player.setVelocityY(-450);
}

4. Colliders vs overlaps (separate vs detect)

// Push apart and react: player vs enemies.
this.physics.add.collider(this.player, this.enemies, (player, enemy) => {
  this.handleHit(player, enemy);
});

// Detect without pushing: collect coins. The 4th arg is an optional
// process callback returning a boolean to filter pairs before the main callback.
this.physics.add.overlap(this.player, this.coins, (player, coin) => {
  coin.disableBody(true, true);              // deactivate + hide
  this.registry.inc('score', 10);
});

5. A group of moving objects

this.bullets = this.physics.add.group({
  defaultKey: 'bullet',
  maxSize: 30                  // pool size; reuse instead of allocating
});

fire(x, y) {
  const bullet = this.bullets.get(x, y);     // reuses a dead bullet if available
  if (!bullet) return;
  bullet.enableBody(true, x, y, true, true);
  bullet.setVelocityY(-500);
}

Pitfalls

• Sprite ignores physics → it was added with this.add.sprite instead of

this.physics.add.sprite (or this.physics.add.existing(obj)), so it has no body.

• Setting sprite.x directly fights the engine → move dynamic bodies with

setVelocity/setAcceleration. Direct position writes can tunnel through colliders.

• Diagonal movement is faster → independent X and Y velocities add up; normalise

the velocity vector and rescale to the intended speed.

• Platforms get pushed by the player → use a staticGroup, or set

body.setImmovable(true) on a dynamic platform.

• onFloor() is always false → the body needs something to collide with; add the

collider against the ground/platforms before checking, and ensure gravity is on.

• Moved a static body but collisions are stale → static bodies don't auto-sync;

call body.updateFromGameObject() (or refreshBody() on the game object).

• Collider added every frame → register collider/overlap once in create,

not in update.

References

• For body anatomy and tuning (drag, bounce, max velocity, custom setSize/

setCircle/setOffset hitboxes, collision categories/masks, and worldbounds

events), read references/bodies-and-collision.md.

Related skills

• phaser-core — game config, scenes, loader, cameras (the prerequisite setup).
• physics-tuning — engine-agnostic feel (fixed timestep, tunneling, jitter).
• platformer / tower-defense — genres that compose this skill.
• level-design — laying out tile/platform geometry these bodies collide with.