html {
     background: radial-gradient(circle, #FF8961, #FFFB89, #74BDCB, #0E42C4) fixed;
}

h1 {
    text-align: center;
    font-size: 4rem;
}

#tiles {
    width: 400px;
    margin: 0 auto;
    position: relative;
    background-color: grey;
    padding: 10px;
    border-radius: 0.5rem;
}

.selected {
    background-color: grey;
    border: none;
    color: grey;
}

.btn {
    font-size: 30px;
    font-weight: bold;
    height: 80px;
    width: 25%;
    cursor: pointer;
    border-radius: 8px;
    border-style: double;
}