*{
    box-sizing: border-box;
    margin: 0;
    padding: 0;
}
body{
    display: flex;
    justify-content: center;
    align-items: center;
    flex-direction: column;
    height: 100vh;
    background: #FFD54F;
}
#countdown{
    color: #000;
    font-size:7em;
    background: #fff;
    padding: 10px 15px;
    border-radius: 10px;
    animation: up-down 5s linear infinite;
}
p{
    font-size: 24px;
}
div span{
    font-size: 3em;
}
@keyframes up-down{
    0%{
        transform: translateY(0) ;
    }
    50%{
        transform: translateY(-100px);
    }
}