text: function contain(sprite, container) {
  
    //Create a `Set` called `collision` to keep track of the
    //boundaries with which the sprite is colliding
    var collision = new Set();
  
    //Left
    if (sprite.x < container.x) {
      sprite.x = container.x;
      collision.add("left");
    }
  
    //Top
    if (sprite.y < container.y) {
      sprite.y = container.y;
      collision.add("top");
    }
  
    //Right
    if (sprite.x + sprite.width > container.width) {
      sprite.x = container.width - sprite.width;
      collision.add("right");
    }
  
    //Bottom
    if (sprite.y + sprite.height > container.height) {
      sprite.y = container.height - sprite.height;
      collision.add("bottom");
    }
  
    //If there were no collisions, set `collision` to `undefined`
    if (collision.size === 0) collision = undefined;
  
    //Return the `collision` value
    return collision;
  }
  
  