code: function ( rect1, rect2 ) {
  
      let overlapX = Math.max ( 0, Math.min ( rect1.right, rect2.right ) - Math.max ( rect1.left, rect2.left ) ),
          overlapY = Math.max ( 0, Math.min ( rect1.bottom, rect2.bottom ) - Math.max ( rect1.top, rect2.top ) );
  
      return overlapX * overlapY;
  
    }
docs: /* UTILITIES