html, body {
  margin: 0;
  padding: 0;
  width: 100%;
  height: 100%;
  line-height: 1;
}
img {
  display: block;
  width: 100%;
  height: 100%;
}
.link {
  position: absolute;
  top: 74%;
  left: 0;
  right: 0;
  margin: 0 auto;
  width: 47%;
  height: 8%;
  -webkit-tap-highlight-color: rgba(0, 0, 0, 0);
}
.img-btn {
margin-top:20%;
  width: 100%;
  height: 100%;
  background-image: url('image/btn-2.png');
  background-size: 100% 100%;
  background-repeat: no-repeat;
}
.step {
  position: relative;
  margin: 0 auto;
  width: 100%;
  height: 100%;
  text-align: center;
}
.step>img {
  box-sizing: border-box;
  margin-bottom: 20px;
  padding: 0 20px;
  height: auto;
}
.step>img:first-child {
  margin-bottom: 0
}
.mask {
  display: none;
  position: fixed;
  top: 0;
  bottom: 0;
  right: 0;
  left: 0;
  background: rgba(0, 0, 0, 1);
  z-index: 1000;
}
.mask>img {
  margin: 15% auto;
  width: 100%;
  height: auto;
  z-index: 1100;
}
@media only screen and (device-width: 375px) and (device-height: 812px) and (-webkit-device-pixel-ratio: 3) {
  .link {
      top: 75%;
      height: 7%;
  }
}