index.css

body {
    height: 100vh;
    margin: auto;
    text-align: center;
    background: url('https://wallpaperaccess.com/full/562430.jpg');
    background-repeat: no-repeat;
    background-size: cover;
    background-attachment: fixed;
    color: white;
}

h1 {
    background-color: rgba(0, 0, 0, 0.3);
    width: 450px;
    margin: 2rem auto;
    padding: 1rem 0.5rem;
}

header {
    width: 450px;
    background: white;
    border-radius: 10px;
    margin: auto;
    height: 475px;
}

header:hover {
    box-shadow: 0 0 5px 2px rgba(0, 0, 0, 0.3)
}

h4 {
    background-color: #26a69a;
    border-bottom: 1px solid #333;
    padding: 1rem;
    font-size: 30px;
}

li {
    padding: 1rem;
    margin: 1rem 0.5rem;
    border: 1px solid #666;
    border-radius: 3px;
    transition: background-color 0.2s ease-in;
}

li:hover {
    background-color: #26a69a;
    box-shadow: 0 0 5px 2px rgba(0, 0, 0, 0.3);
    transition: background-color 0.2s ease-in;
}

label {
    font-size: 1.3rem;
    transition: .3s ease-in;
}

label:hover {
    cursor: pointer;
    color: black;
}

input:checked ~ label {
    color: blue;
}

.btn {
    margin-top: 2rem;
    width: 450px;
    box-shadow: 0 0 5px 2px rgba(0, 0, 0, 0.3) ;
}