/* 页脚 */
footer {
    text-align: center;
    margin-top: 50px;
    padding: 20px;
    color: #a9b7c6;
    font-size: 0.9rem;
    border-top: 1px solid rgba(255,255,255,0.1);
}

/* 返回顶部按钮 */
.back-to-top {
    position: fixed;
    bottom: 30px;
    right: 30px;
    width: 50px;
    height: 50px;
    background: linear-gradient(135deg, #00c3ff, #00f2fe);
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    color: #0a0818;
    font-size: 20px;
    cursor: pointer;
    z-index: 99;
    box-shadow: 0 0 15px rgba(0, 195, 255, 0.5);
    transition: all 0.3s ease;
    opacity: 0;
    transform: translateY(20px);
}

.back-to-top.visible {
    opacity: 1;
    transform: translateY(0);
}

.back-to-top:hover {
    transform: translateY(-5px) scale(1.1);
}