static intersects(a, b) {
    return (
      a.left < b.left + b.width && b.left < a.left + a.width && a.top < b.top + b.height && b.top < a.top + a.height
    );
  }
Returns whether two rectangles intersect.
@param {Rect} a A Rectangle.
@param {Rect} b A Rectangle.
@return {boolean} Whether a and b intersect.