*{
    margin: 0;
    padding: 0;
    font-family:'黑体';
}

a{
    text-decoration: none;
}
body{
    background:gray url(./wallhaven-672873.jpg)  center center;
    background-size: cover; /*让背景图片自适应屏幕*/
}
  
kbd div{
    position: absolute;
    right: 4px;
    bottom:2px;
    display: none;
    cursor:default;
}
kbd:hover div{
    display: inline-block;
}
#zzz div:nth-child(2){
    margin-left:-22px;
}
#zzz div:nth-child(3){
    margin-left: -80px;
}
#zzz{
    display: inline-block;
}
main{
    text-align: center;
    display: flex;
    justify-content:center;
    align-items: center; 
    height: 100vh;   /* viewport height 视口高度*/
}
.keys{
    width: 55px;
    height: 38px;
    background: linear-gradient(to bottom,#292929 0%,#111111 100%);
    border: 1px solid #373737;
    color: #c5c5c5;
    border-radius: 7px;
    box-shadow: 0 0 0 1px #1a1b1c,0 0 0 2px #1f2020,0 3px 1px 2px #696969,0 0 0 2px #1a1b1c;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    margin: 8px;
    text-transform: uppercase;
    position: relative;
}
.keys img{
    width: 16px;
    height: 16px;
    position: absolute;
    bottom: 2px;
    left: 3px;
}
.keys span{
    position: absolute;
    top: 2px;
    left: 4px;
}