/* 页脚样式 - 默认 (电脑设备) */
footer {
    background-color: rgba(51, 51, 51, 0.5); /* 半透明背景 */
    color: white;
    display: flex;
    justify-content: center;
    align-items: center;
    padding: 0px;
    position: fixed;
    left: 0;
    right: 0;
    bottom: 0;
    font-size: 14px;
    max-height: 30px;
    z-index: 2000;
}