/*核心代碼*//*分析動畫，其實動畫只有兩次的執行*/   var for_index = 1;//記錄當前執行動畫的序列   var interval = setInterval(function(){    if(for_index == 1){     if(squre4.x == origin_squre.x - step * 2){      for_index = 2;     }else{      squre2.x -= 2;      squre2.y += 1;      squre4.x += 2;      squre4.y -= 1;     }    }else if(for_index == 2){     if(squre4.x == origin_squre.x){      for_index = 1;      /*重置方塊位置信息到初始值*/      init_squre(origin_squre.x,origin_squre.y);     }else{      squre3.x -= 2;      squre3.y -= 1;      squre2.x -= 2;      squre2.y -= 1;      squre4.x += 2;      squre4.y += 1;      squre1.x += 2;      squre1.y += 1;     }    }    ctx.clearRect(0,0,canvas.width,canvas.height);    /*重繪方塊*/    if(for_index == 1 || for_index == 2){     draw_squre(squre4);     draw_squre(squre1);     draw_squre(squre3);     draw_squre(squre2);    }    /*重繪陰影*/    get_shaow_pos();    for(var i in shaow_begin){     draw_shaow(shaow_begin[i]);    }   },1000 / 24);