#sw10_floating_back_button {
    position: fixed;
    top: 50%;
    transform: translateY(-50%);
    z-index: 50;
    /* Default for small screens, aligns with padding */
    right: 1.25rem; 
}

/* On screens wider than 480px, calculate the position */
@media (min-width: 481px) {
    #sw10_floating_back_button {
        /* (100vw - 480px) / 2 gives the size of the margin on each side. */
        /* We add the desired padding (1.25rem) to this margin. */
        right: calc((100vw - 480px) / 2 + 1.25rem);
    }
}