style.css

*{
    margin: 0;
    padding: 0;
}
.icon {
       width: 1em; height: 1em;
       vertical-align: -0.15em;
       fill: currentColor;
       overflow: hidden;
    }

body {
    background: grey url(http://p86y5hc6k.bkt.clouddn.com/page.jpg) no-repeat center center; 
    background-size: cover;
    height: 100vh;
    display: flex;
    flex-direction: column;
}
/* header{
    height: 200px;
    display: flex;
    justify-content: center;
    align-items: center;
}
header div{
    max-width: 926px;
    height: 66px;
    background: #fff;
}
header input{
    height: 60px;
    max-width: 400px;
    border: transparent;
    font-size: 2em;
    padding-left: .2em;
} */
kbd {
    display: inline-block;
    width: 6em;
    height: 4em;
    text-transform: uppercase;
    position: relative;
    
}

kbd > button {
    display: none;
    position: absolute;
    right: 4px;
    bottom: 4px;
    border-radius: 4px;
    height: 16px;
    width: 16px;
    border: transparent;
    cursor: pointer;
    background: rgba(129, 121, 121, 0.8)
}
kbd > img {
    position: absolute;
    left: 4px;
    bottom: 4px;
    height: 16px;
    width: 16px;
    border-radius: 4px;
}

kbd:hover > button {
    display: inline-block;
}

main {
    flex-grow: 1;
    text-align: center;
    display: flex;
    justify-content: center;
    align-items: center;
}

#main {
    display: inline-block;
    padding: 48px;
    background-color: rgba(255, 255, 255, 0.3);
    border-radius: 8px;
}

#main > div:nth-child(2){
    margin-left: 2em;
}

#main > div:nth-child(3){
    margin-left: 4em;
}

.key {
    width: 47px;
    height: 69px;
    border-radius: 8px;
    padding: 0 12px;
    line-height: 69px;
    float: left;
    position: relative;
    margin: 0 12px 12px 0;
    background-color: #000;
    color: #fff;
    text-align: center;
    font-size: 24px;
    box-shadow: 2px 2px 2px rgba(0, 0, 0, 0.5);
    font-family: Helvetica;
}