body {
    margin: 0;
    background-color: #222;
    overflow: hidden;
}
.theme-default {
    background: linear-gradient(
        to right,
        rgb(46, 71, 63) 0%,
        rgb(47, 77, 53) 100%
    );
    background-color: #222;
}
.theme-fishes {
    background: linear-gradient(
        to bottom,
        rgb(20, 94, 114) 0%,
        rgb(30, 58, 120) 100%
    );
    background-color: #222;
}
.theme-birds {
    background: linear-gradient(
        to bottom,
        rgb(168, 216, 255) 30%,
        rgb(251, 255, 204) 100%
    );
    background-color: #222;
}

#menu {
    position: absolute;
    top: 0;
    right: 0;
    padding: 10px;
}
button {
    font-size: 20px;
    padding: 5px;
    border-radius: 10px;
    border: none;
    cursor: pointer;
    background-color: #222;
}