header {
    position: fixed;
    top: 1px;
    left: 1px;
    width: 100%;
    height: 100px;
    border: 1px;
    border-style: solid;
    border-color: #333333;
    background-color: #1d1b1b;
    z-index: 100;
}
header h1{
    position: absolute;
    left: 20px;
    line-height: 50px;
}
header li{
    display: inline;
    margin-right: 4vw;
    padding: 20px;
}
header ul{
    position: absolute;
    right: 5vw;
    top: 0;
    line-height: 100px;
}
.first {
    position: absolute;
    top: 100px;
    justify-content: center;
    height: 512px;
    width: 100%;
    background-image: url("pic/bg.png");
    background-position: center;
    background-size: 1024px 512px;
    /* background-color: #112D52; */
}
.first h2 {
    font-size: 50px;
    position: relative;
    top: 50%;
    text-align: center;
}
.first strong {
    color: #308005;
}
.feature {
    position: absolute;
    bottom: -70%;
    width: 100%;
    height: 310px;
    padding-bottom: 40px;
}
.feature .fl h3 strong{
    color: #52cb11;
    font-size: 30px;
}
.feature h2 {
    position: relative;
    bottom: 285px;
    font-size: 30px;
    text-align: center;
    background-color: #1d1b1b;
    border: 1px;
    border-style: solid;
    border-color: #333333;
}
.feature .fl {
    display: flex;
    justify-content: space-between;
    align-items: center;
    text-align: center;
}
.feature .fl div {
    position: relative;
    bottom: 285px;
}
.feature .fl img{
    border: 1px;
    border-color: #333333;
    border-style: solid;
}
.feature .fl p{
    font-size: large;
    font-family: Arial, Helvetica, sans-serif;
}
.start {
    position: absolute;
    bottom: -90%;
    display: flex;
    width: 100%;
    height: 80px;
    display: block;
    text-align: center;
}
.start a{
    height: 80px;
    width: 100px;
    justify-content: center;
    background-color: #ffffff;
    padding-bottom: 20px;
    padding-top: 20px;
    padding-right: 80px;
    padding-left: 80px;
    border: 1px;
    border-color: #333333;
    border-style: solid;
    border-radius: 10px;
    color: black;
}
.start a:hover{
    text-decoration: none;
    background-color: rgb(176, 176, 176);
}