style.css

html, body {
    margin: 0;
    padding: 0;
    width: 100%;
    height: 100%;
}
body {
    font-family: system-ui;
    line-height: 1em;
    background: #eee;
}

div {
    margin: 0 auto;
    padding: 40px 25px;
    width: calc(100% - 50px);
    max-width: 450px;
    min-height: calc(100% - 80px);
    background: #fff;
    text-align: center;
}
h1 {
    margin: 40px auto 15px;
    padding: 0;
}
p {
    margin: 0 0 35px;
    font-size: 12px;
}
ul {
    margin: 0;
    padding: 0;
    list-style: none;
}
ul li {
    margin: 0 0 15px;
}
ul li a {
    display: block;
    padding: 19px;
    font-size: 16px;
    border-radius: 5px;
    color: #000;
    text-decoration: none;
    background: #eee;
}
ul li a:hover {
    background: linear-gradient(to top right, #90ff00, #fff700);
}