header {
    width: 100%;
}

footer {
    margin: 0;
}

main {
    display: flex;
}

.game {
    flex: 1;
    background-color: #000;
}

.back {
    width: var(--button);
    height: var(--button);
    position: fixed;
    right: 0;
    top: 0;
    background-color: #00000062;
    z-index: 999;
    display: none;
}

@media only screen and (max-device-width: 768px) and (orientation: landscape) {
    header,footer {
        display: none;
    }

    .back {
        display: block;
    }
}