[Specification] 3 * 5
  Mopping background background's size can be customized size shed your shadow!
   Background General Dimensions (W * H)

     1.5 * 1.5 * 1.5 m 2 m;;;; 2;; 1.5 * 2.5 m * 2.5 m * 3 m;; 2;;;; 2.5 * 2.5 * 3 m 3.75 m 3.75 m;;;; 3 * 3 * 4.5 m * 5 m;; 3;; 3;; 4 * 6 m * 6 m;