.btn-back-to-top {
    position: fixed;
    right: 1rem;
    bottom: 1rem;
    display: none;
    border: none;
    border-radius: 50%;
    width: 50px;
    height: 50px;
    font-size: 2em;
    cursor: pointer;
    box-shadow: 0 2px 8px rgba(0,0,0,0.2);
    z-index: 1000;
    transition: opacity 0.3s;
}

.btn-back-to-top.show {
    display: block;
    opacity: 1;
}

.btn-back-to-top.hide {
    opacity: 0;
}