html, body, #main {
    margin: 0;
    padding: 0;
    width: 100vw;
    height: 100vh;
    overflow: hidden;
    /* 深色背景以突出地球 */
    background-color: #000;
    color: #fff;
    font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, 'Helvetica Neue', Arial, sans-serif;
}