Custom Bounds

class Example extends Phaser.Scene
{
    preload ()
    {
        this.load.setBaseURL('https://cdn.phaserfiles.com/v410');
        this.load.image('clown', 'assets/sprites/clown.png');
        this.load.image('monitor', 'assets/demoscene/monitor.png');
        this.load.image('sky', 'assets/skies/space2.png');
        this.load.spritesheet('ball', 'assets/sprites/balls.png', { frameWidth: 17, frameHeight: 17 });
    }

    create ()
    {
        this.add.image(400, 300, 'sky');

        // Balls in the default world bounds

        const balls = this.physics.add.group({
            key: 'ball',
            frame: [ 0, 1, 2, 3, 4 ],
            frameQuantity: 10,
            bounceX: 1,
            bounceY: 1,
            collideWorldBounds: true,
            velocityX: 100,
            velocityY: 100
        });

        Phaser.Actions.RandomRectangle(balls.getChildren(), this.physics.world.bounds);

        this.add.image(400, 300, 'monitor');

        // Clown in smaller bounds

        const clown = this.physics.add.image(400, 300, 'clown')
            .setCollideWorldBounds(true, 1, 1)
            .setVelocity(100, -100);

        clown.body.setBoundsRectangle(new Phaser.Geom.Rectangle(254, 186, 292, 210));
    }
}

const config = {
    scale: { mode: Phaser.Scale.FIT },
    type: Phaser.AUTO,
    width: 800,
    height: 600,
    parent: 'game-container',
    physics: {
        default: 'arcade',
        arcade: {
            debug: false,
            gravity: { y: 200 }
        }
    },
    scene: Example
};

const game = new Phaser.Game(config);