body{
    font-size: 50px;
    text-align:center;
    /**/
    background-image: url("../images/indexhaikei.jpg");
    background-size: cover;
}

.btn_box{
    position: absolute;
    top: 50%;
    left: 50%;
    transform: translate(-50%, -50%);
    width: 100%;
    margin: 0;
  }
  
  .btn{
    color: #000;
    font-size: 24px;
    text-align: center;
    line-height: 78px;
    letter-spacing: 3px;
    width: 400px;
    height: 78px;
    background: #fce38a;
    margin: auto;
    cursor: pointer;
    border-radius: 100px;
  }
  
  /*アニメーション*/
  .animation{
    animation: gatagata .2s infinite;
    scale: 1;
  }
  
  @keyframes gatagata{
   0%{transform:translateY(0)}
   25%{transform:translate(0px, 2px) rotateZ(1deg)}
   50%{transform:translate(0px, 2px) rotateZ(0deg)}
   75%{transform:translate(2px, 2px) rotateZ(-1deg)}
   100%{transform:translate(0px, 0px) rotateZ(0deg)}
  }