/* 回到顶部按钮样式 */
.back-to-top-btn {
    position: fixed;
    bottom: 28%;
    right: 20px;
    width: 40px;
    height: 40px;
    border-radius: 50%;
    background-color: rgba(10, 10, 10, .4);
    color: #fff;
    border: none;
    box-shadow: 0 2px 10px rgba(0, 0, 0, 0.2);
    cursor: pointer;
    display: none; /* 默认隐藏 */
    z-index: 100;
    transition: all 0.3s ease;
    opacity: 0.8;
}

.back-to-top-btn:hover {
    background-color: #3a70c0;
    opacity: 1;
    transform: translateY(-3px);
}

.back-to-top-btn .iconfont {
    font-size: 18px;
    line-height: 40px;
}