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%;
    }
}