*{
  margin:0
}
.button1{
  visibility:hidden;
}

.button2{
  position: absolute;
  top: 75%;
  left: 34%;
  width: 420px;
  height: 100px;
  z-index: 100;
  border-radius: 50px;
  background-color:rgba(255,235,59, 0.95);
  z-index: 2;
}

.bak{
  background:url(osirodesu.png);
  background-size: cover;
  background-attachment: fixed;
  background-position: center center;
  background-repeat: no-repeat;
  position: absolute;
  width: 100%;
  height: 100vh;
  z-index: 1;
}

.rogo{
  width: 65%;
  height: auto;
  position: absolute;
  z-index: 2;
  left: 15%;
  top: 10%;
}

@media screen and (max-width: 479px) {
  .button1{
    position: absolute;
    top: 80%;
    left: 10%;
    width: 80%;
    height: 80px;
    z-index: 100;
    visibility:visible;
    border-radius: 50px;
    background-color:rgba(255,235,59, 0.95);
    z-index: 2;
  }
  
  .button2{
    visibility:hidden; 
    top: 75%;
    left: 10%;
    width: 0;
    height: 0;
  }
  
  .bak{
    background:url(image0.jpg);
    background-size: cover;
    background-attachment: fixed;
    background-position: center center;
    background-repeat: no-repeat;
    position: absolute;
    width: 100%;
    height: 100vh;
    z-index: 1;
  }
  
  .rogo{
    width: auto;
    height: 15%;
    position: absolute;
    z-index: 2;
    left: 10%;
    top:10%;
  }
}