header {position: fixed; top: 20px; left: 0; width: 100%; z-index: 9999;}
header .logo {width: 139px; height: auto;}

/* fixed_btn */
.fixed_btn {animation: heartbeat 1.5s ease-in-out infinite both; position: fixed; bottom: 50px; right: 50px; display: flex; flex-flow: column; gap: 10px; z-index: 6;}
@keyframes heartbeat {
  from {
    -webkit-transform: scale(1);
            transform: scale(1);
    -webkit-transform-origin: center center;
            transform-origin: center center;
    -webkit-animation-timing-function: ease-out;
            animation-timing-function: ease-out;
  }
  10% {
    -webkit-transform: scale(0.91);
            transform: scale(0.91);
    -webkit-animation-timing-function: ease-in;
            animation-timing-function: ease-in;
  }
  17% {
    -webkit-transform: scale(0.98);
            transform: scale(0.98);
    -webkit-animation-timing-function: ease-out;
            animation-timing-function: ease-out;
  }
  33% {
    -webkit-transform: scale(0.87);
            transform: scale(0.87);
    -webkit-animation-timing-function: ease-in;
            animation-timing-function: ease-in;
  }
  45% {
    -webkit-transform: scale(1);
            transform: scale(1);
    -webkit-animation-timing-function: ease-out;
            animation-timing-function: ease-out;
  }
}
.fixed_btn a {display: block; width: 100px; height: auto;}
.fixed_btn a img {width: 100%; height: auto;}