#btn {
  position: absolute;
  top: 350px;
  left:170px;
  display:none;
  z-index: 4;
  }

#canvas_wrapper{
    position: relative;
    width:465px;
    top: 0px;
    left:0px;
    margin:0 auto;
  }

  .canvas{
    z-index: 3;
  }

#back{
    position: absolute;
    width:465px;
    top: 0px;
    left:60px;
    margin:0 auto;
    z-index: -1;
  }

#end_s{
    position: absolute;
    top: 0px;
    left:60px;
    z-index: 3;
    display:none;
  }

#end_f{
    position: absolute;
    top: 0px;
    left:60px;
    z-index: 3;
    display:none;
  }

  #top{
    position: relative;
    width:465px;
    top: 0px;
    left:0px;
    margin:0 auto;
  }