@keyframes fade{
    0% { opacity: 0;}
    100% {opacity: 1;}
}

body{
    padding: 0;
    margin: 0;
}

h1{
    margin: 0;
}

main section{
    display: flex;
    justify-content: center;
    align-items: center;
    height: 100vh;
    position: fixed;
    width: 100%;
    transition: 1s;
    flex-direction: column;
}

main section:first-child{
    z-index:1;
}

section div{
    width: 100px;
    height: 100px;
    background-color: #000000;
}