section.announcement-bar {
    display: flex;
    justify-content: center;
    align-items: center;
    background-color: var(--color-surface);
    color: var(--color-primary);
    font-size: 0.7rem;
    padding: 0.5rem 0;
    width: 100%;
    position: relative;
    z-index: 1;
    height: var(--height-announcement-bar);
}

a.join {
    margin: 0 var(--space-1);
    cursor: pointer;
    /* 下划线 */
    text-decoration: underline;
    font-weight: bold;
}