body {
    align-items: center;
    background: #2F2F2F;
    display: flex;
    min-height: 100vh;
}
h1 {
    font-size: 1em;
}
form {
    background: #fff;
    margin: auto;
    max-width: 100%;
    overflow: hidden;
    position: relative;
    width: 20em;
}
form::before {
    background: url('/favicon.png') 50% 0 no-repeat;
    background-size: 64px;
    content: "";
    height: 64px;
    left: calc(50% - 32px);
    position: absolute;
    top: 2em;
    transform: rotate(0deg);
    transform-origin: 50% calc(0);
    transition: transform 1s;
    width: 64px;
    /*z-index: -1;*/
}
form:hover::before {
    transform: rotate(360deg);

}
fieldset {
    padding: calc(4em + 64px) 2em 2em;
}
input[type="submit"] {
    width: 100%;
}