/* 基本样式 */
body {
    font-family: "Segoe UI", Tahoma, Geneva, Verdana, sans-serif;
    margin: 0;
    padding: 0;
    background-color: #f4f4f4;
    color: #333;
}

header {
    background-color: #0070f3;
    color: white;
    padding: 60px 20px 20px 20px; /* 留出导航高度 */
    text-align: center;
}

section {
    padding: 40px 20px;
    border-bottom: 1px solid #ccc;
    scroll-margin-top: 70px;
}

h2 {
    color: #0070f3;
}

/* 公告弹窗 */
.modal {
    position: fixed;
    top:0; left:0; right:0; bottom:0;
    background: rgba(0,0,0,0.6);
    display: flex;
    align-items: center;
    justify-content: center;
    z-index: 1000;
    opacity:0;
    visibility:hidden;
    transition: 0.3s;
}

.modal.show {
    opacity:1;
    visibility:visible;
}

.modal-content {
    background:white;
    padding:30px;
    border-radius:8px;
    text-align:center;
    width:80%;
    max-width:400px;
}

button {
    margin-top:20px;
    padding:10px 20px;
    border:none;
    background-color:#0070f3;
    color:white;
    cursor:pointer;
    border-radius:5px;
}

button:hover { background-color:#005bb5; }

.hidden { display:none; }

/* 导航栏 */
nav {
    position:fixed; top:0; width:100%;
    background: rgba(0,112,243,0.9);
    color:white; z-index:999;
    display:flex; justify-content:center;
    padding:10px 0;
}

nav ul { list-style:none; display:flex; gap:30px; padding:0; margin:0; }

nav ul li a { color:white; text-decoration:none; font-weight:bold; font-size:16px; }

nav ul li a:hover { text-decoration:underline; }

/* 音乐播放器 */
#music-player {
    position:fixed;
    bottom:10px; right:10px;
    background:rgba(0,0,0,0.7);
    padding:10px;
    border-radius:5px;
    color:white;
    font-size:14px;
    max-width:200px;
}

#music-player button {
    background-color:#fff;
    color:#0070f3;
    padding:3px 8px;
    margin:2px;
    font-size:12px;
    border-radius:3px;
}

/* 播放列表折叠 */
#playlist {
    list-style:none;
    margin-top:5px;
    padding-left:0;
    max-height:150px;
    overflow-y:auto;
    background: rgba(255,255,255,0.9);
    color:#0070f3;
    border-radius:4px;
    display:block;
}

#playlist.collapsed {
    display:none;
}

#playlist li {
    cursor:pointer;
    padding:4px 6px;
}

#playlist li.active {
    background-color:#0070f3;
    color:white;
}