/**
 * @typedef {object} Phaser.Types.Physics.Impact.WorldWalls
 * @since 3.0.0
 *
 * @property {?Phaser.Physics.Impact.Body} left - The left-side wall of the world bounds.
 * @property {?Phaser.Physics.Impact.Body} right - The right-side wall of the world bounds.
 * @property {?Phaser.Physics.Impact.Body} top - The top wall of the world bounds.
 * @property {?Phaser.Physics.Impact.Body} bottom - The bottom wall of the world bounds.
 */
