html {
    font-size: 10px;
}

#central {
    width: 30rem;
    height: 30rem;
    background-color: lightgoldenrodyellow;
    background: url("icon.png");
    background: no-repeat center url("icon.png");
    background-size: 96px;
    background-size: 100%;
    background: radial-gradient(circle, magenta, gold, cyan, lime);
    border-radius: 50%
}

#not-central {
    width: 30rem;
    height: 30rem;
    background: radial-gradient(red, gold, magenta);
    border-radius: 50%;
}

a {
    font-size: 12px;
    line-height: 1;
    padding: 15px;
    position: relative;
    top: 50%;
    left: 33.33%;
}

a:hover {
    outline: 15px solid aquamarine;
}