/* 返回顶部按钮样式 */
        .back-to-top {
            position: fixed;
            bottom: 40px;
            right: 40px;
            width: 50px;
            height: 50px;
            background: #007bff;
            color: white;
            border-radius: 50%;
            text-align: center;
            cursor: pointer;
            opacity: 0;
            visibility: hidden;
            transition: all 0.3s ease;
            z-index: 9999;
            display: flex;
            align-items: center;
            justify-content: center;
            box-shadow: 0 2px 5px rgba(0,0,0,0.3);
        }

        .back-to-top:hover {
            background: #0056b3;
            transform: translateY(-2px);
        }

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

        /* 箭头样式 */
        .toparrow {
            width: 0;
            height: 0;
            border-left: 12px solid transparent;
            border-right: 12px solid transparent;
            border-bottom: 12px solid white;
            margin-top: -4px;
        }