.banner{position:relative}
.banner-title {
    position: absolute;
    left: 50%;
    top: 50%;
    text-align: center;
    transform: translate(-50%,-50%);
    color: #fff;
}
.introduct {
    font-size: 6rem;
    font-weight: bold
}
.origin {
    padding: 0 25%;
    position: relative;
    margin: 13rem 0;
}
.origin .num{
    position: absolute;
    transform: rotate(90deg);
    transform-origin: left top;
    left: 16.66%;
    top: 5px;
    font-size: .6rem;
}
.chTitle {
    font-size: 2.75rem;
    margin-bottom:2rem
}
.green {
    color: #007765;
}
.desc {
    font-size: 1rem;
    margin-top: 1rem;
}
.ideal {
    background: #007764;
    color: #fff;
    text-align: center;
    padding: 10rem 0;
}
.coupling {
    display: flex;
    margin: auto;
    justify-content: center;
    margin-top:5rem
}
.coupling-i {
    border: 1px solid rgba(0,0,0,0.3);
    width: 18%;
    border-radius: 50%;
    height: 18vw;
    background: rgba(0,0,0,.03);
    display: flex;
    flex-direction: column;
    justify-content: center;
}
.coupling-i:nth-child(2){margin:0 -2%}
.coupling-eng {
    color: rgba(0,0,0,.5);
    margin-bottom: 2rem;
    margin-top: -3rem;
}
.coupling-i h3{font-size:1.25rem;font-weight:bold}
.origin .img-fill{margin-top:5rem}