.back-to-top {
    position: fixed;
    bottom: 20px;
    /* --- KEY CHANGE HERE --- */
    /* REMOVED: right: 20px; */
    left: 20px;
    /* ----------------------- */
    display: none;
    background-color: #1b9c85;
    color: #fff;
    padding: 10px 15px;
    border-radius: 5px;
    z-index: 9999;
}

.back-to-top:hover {
    background-color: #005a87;
}

/* Show on mobile and tablet */
@media (max-width: 768px) {
    .back-to-top {
        display: block;
    }
}