*{
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}
body{
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    background-image: url(night.jpg);
    background-repeat: no-repeat;
    background-size: cover;
    background-position: center;
}
#clock{
    display: flex;
    align-items: center;
    justify-content: center;
    font-size:51px;
    padding: 10px;
    color: #fff;
    width: 270px;
    height: 150px;
    background: rgba(255, 255, 255, .1);
    border: 1px solid rgba(255, 255, 255, .1);
    backdrop-filter: blur(5px);
    box-shadow: 
    5px 5px 2px rgba(255, 255, 255, .1),
    -5px -5px 2px rgba(255, 255, 255, .1);
    border-radius: 10px;
    animation: up-down 7s linear infinite;
}
@keyframes up-down{
    0%, 100%{
        transform: translateY(0) scale(1);
    }
    50%{
        transform: translateY(-50px) scale(1.3);
    }
}