.pc_box{
    margin: -3840px -50px 3700px -50px;
    position: relative;
    display: block;
}
.pc_box a{
    display: inline-block;
    width: 48%;
    height: 94px;
    margin: 0 1%;
    text-align: center;
    /*background-color: red;
    opacity: .5;*/
    padding: 0;
    line-height: 1;
}


@media screen and (max-width: 768px) {
  .pc_box,#main_pict{
    display: none;
  }
  .sp_box{
    margin: 0 -28px;
  }
  .sp_box img{
    display: block;
    margin: 0 auto;
    padding: 0;
    width: 100%;
  }
  .howto{
    display: block;
    margin: 0 auto;
    padding: 62% 0 30% 0;
    width: 100%;
    background-image: url(howto_sp.jpg);
    background-position: top center;
    background-repeat: no-repeat;
    background-size: 100%;

  }
  .howto a{
    display: block;
    margin: 0 auto 19% auto;
    padding: 0;
    width: 74%;
  }
}