.back-to-top {
    position: fixed;
    bottom: 40px;
    right: 40px;
    width: 46px;
    height: 46px;
    background-color: #FF6B00;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: white;
    text-decoration: none;
    opacity: 0;
    visibility: hidden;
    transition: all 0.3s ease;
    z-index: 9999;
    cursor: pointer;
}

.back-to-top.show {
    opacity: 1;
    visibility: visible;
}

.back-to-top:hover {
    background-color: #FF7B1A;
    transform: translateY(-2px);
}

.back-to-top:active {
    transform: translateY(0);
}

.back-to-top i {
    font-size: 20px;
    color: white;
    line-height: 1;
    transition: transform 0.2s ease;
}

.back-to-top:hover i {
    transform: translateY(-2px);
}

@media (max-width: 768px) {
    .back-to-top {
        bottom: 25px;
        right: 25px;
        width: 42px;
        height: 42px;
    }

    .back-to-top i {
        font-size: 18px;
    }
}

/* 暗色模式 */
@media (prefers-color-scheme: dark) {
    .back-to-top {
        background-color: #FF6B00;
        box-shadow: 0 4px 18px rgba(255, 107, 0, 0.15);
    }
    
    .back-to-top:hover {
        background-color: #FF7B1A;
        box-shadow: 0 6px 24px rgba(255, 107, 0, 0.25);
    }
}