/* ============================================================
   网易云音乐 — 官方资讯与展示型静态官网
   设计规范：需求文档 第四章（色彩 / 字体 / 圆角 / 间距）
   响应式：移动端优先，断点 768px、1024px
   无外部依赖：不引用任何 CDN 字体、图标库或 CSS 框架
   ============================================================ */

:root{
    /* 4.1 色彩系统 */
    --primary:#052953;          /* 主色：导航悬停、按钮主色、标题强调、Footer 背景 */
    --primary-light:#007cc2;    /* 主色亮版：链接悬停、次级按钮、导航下拉悬停 */
    --accent:#f60;              /* 强调色：CTA 按钮、评分星标、公告条强调元素 */
    --text:#1a1a1a;             /* 文字主色 */
    --text-black:#000;          /* 导航默认文字 */
    --text-sub:#666;            /* 文字辅色 */
    --text-muted:#999;          /* 更弱辅助文本 */
    --bg:#fff;                  /* 页面背景 */
    --bg-alt:#f5f7fa;           /* 区块交替背景 */

    /* 4.2 字体 */
    --font:system-ui,-apple-system,"PingFang SC","Microsoft YaHei",sans-serif;

    /* 4.3 圆角 */
    --radius-card:12px;
    --radius-btn:8px;
    --radius-pill:999px;

    /* 4.4 间距 */
    --container-max:1200px;
    --nav-max:800px;
    --section-py:48px;          /* 移动端区块内边距 */
    --shadow-sm:0 2px 10px rgba(5,41,83,.06);
    --shadow-md:0 8px 24px rgba(5,41,83,.12);
}

*,*::before,*::after{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;scroll-behavior:smooth}
body{
    margin:0;
    font-family:var(--font);
    font-size:15px;             /* 移动端正文 */
    line-height:1.65;
    color:var(--text);
    background:var(--bg);
}
h1,h2,h3{margin:0 0 12px;line-height:1.3;color:var(--text)}
h1{font-size:28px;font-weight:700}      /* 移动端 */
h2{font-size:22px;font-weight:600}
h3{font-size:18px;font-weight:600}
p{margin:0 0 12px}
ul{margin:0;padding:0;list-style:none}
img{max-width:100%;display:block}
a{color:var(--primary-light);text-decoration:none}
a:hover{color:var(--primary);text-decoration:underline}
table{border-collapse:collapse;width:100%}
.small{font-size:13px}
.sr-only{position:absolute;width:1px;height:1px;padding:0;margin:-1px;overflow:hidden;clip:rect(0 0 0 0);white-space:nowrap;border:0}

/* ---------- 布局容器 ---------- */
.container{width:100%;max-width:var(--container-max);margin:0 auto;padding:0 16px}
.section{padding:var(--section-py) 0}
.section-alt{background:var(--bg-alt)}
.section-head{text-align:center;max-width:760px;margin:0 auto 24px}
.section-head p{color:var(--text-sub);margin:0}

/* ---------- 按钮 ---------- */
.btn{
    display:inline-block;
    padding:10px 24px;          /* 移动端按钮内边距 */
    border:0;
    border-radius:var(--radius-btn);
    font-family:inherit;
    font-size:15px;
    font-weight:600;
    line-height:1.4;
    text-align:center;
    cursor:pointer;
    transition:background-color .2s ease,color .2s ease,opacity .2s ease;
}
.btn:hover{text-decoration:none}
.btn-primary{background:var(--accent);color:#fff}
.btn-primary:hover{background:#e65c00;color:#fff}
.btn-secondary{background:var(--primary);color:#fff}
.btn-secondary:hover{background:var(--primary-light);color:#fff}
.btn-ghost{background:#fff;color:var(--primary);border:1px solid rgba(5,41,83,.25)}
.btn-ghost:hover{background:var(--primary);color:#fff}
.btn-row{display:flex;flex-wrap:wrap;gap:12px}

/* ============================================================
   2.1 顶部导航栏（Sticky Header）
   参考：.nav-container max-width:800px; margin:0 auto;
        列表项 display:inline-block; margin:0 10px;
        链接默认色 #000，悬停色 #052953
   ============================================================ */
.site-header{
    position:sticky;
    top:0;
    z-index:50;
    background:rgba(255,255,255,.96);
    border-bottom:1px solid rgba(5,41,83,.08);
}
.site-header.is-scrolled{box-shadow:0 2px 12px rgba(5,41,83,.12)}
.nav-container{
    max-width:var(--nav-max);
    margin:0 auto;
    padding:0 16px;
    min-height:56px;
    display:flex;
    align-items:center;
    justify-content:space-between;
    gap:12px;
}
.brand{display:flex;align-items:center;gap:8px;color:var(--text-black);font-weight:700;font-size:17px}
.brand:hover{color:var(--primary);text-decoration:none}
.brand img{width:28px;height:28px;border-radius:50%}
.nav-toggle{
    display:inline-flex;
    align-items:center;
    justify-content:center;
    width:40px;height:40px;
    padding:0;
    background:transparent;
    border:1px solid rgba(5,41,83,.15);
    border-radius:var(--radius-btn);
    cursor:pointer;
    color:var(--text-black);
}
.nav-toggle svg{width:20px;height:20px}
.nav-menu{list-style:none;margin:0;padding:0}
.nav-menu li{display:inline-block;margin:0 10px}
.nav-menu a{
    display:inline-block;
    font-size:15.5px;           /* 4.2 导航字号 */
    font-weight:bold;
    color:var(--text-black);
    padding:6px 2px;
}
.nav-menu a:hover,.nav-menu a[aria-current="page"]{color:var(--primary);text-decoration:none}
.nav-cta{padding:8px 20px;font-size:15px}

/* 移动端：全屏抽屉式菜单（无 JS 时默认展开可见） */
.nav-panel{
    display:block;
    position:absolute;
    left:0;right:0;
    top:100%;
    background:#fff;
    border-bottom:1px solid rgba(5,41,83,.1);
    box-shadow:var(--shadow-md);
    padding:8px 16px 16px;
}
.nav-panel .nav-menu li{display:block;margin:0}
.nav-panel .nav-menu a{display:block;padding:12px 4px;border-bottom:1px solid var(--bg-alt)}
.nav-panel .nav-cta-wrap{margin-top:12px}
html.js .nav-panel{display:none}
html.js .nav-panel.is-open{display:block}
.nav-panel .nav-cta{display:block;width:100%}

/* ============================================================
   2.2 Hero 首屏区
   ============================================================ */
.hero{
    background:linear-gradient(160deg,#052953 0%,#0a3f74 55%,#007cc2 140%);
    color:#fff;
    padding:48px 0;             /* 移动端垂直内边距 */
}
.hero h1{color:#fff;margin-bottom:12px}
.hero h1 .hero-accent{display:block;font-size:20px;font-weight:600;color:#a8d8f5;margin-top:8px}
.hero-sub{color:rgba(255,255,255,.82);max-width:56ch}
.hero-stats{display:flex;flex-wrap:wrap;gap:16px;margin:20px 0 24px;padding:0}
.hero-stats li{min-width:44%}
.hero-stats strong{display:block;font-size:22px;font-weight:700;color:#fff}
.hero-stats span{font-size:13px;color:rgba(255,255,255,.75)}
.hero-cta{margin-bottom:28px}

/* 播放器模拟 UI（纯 CSS 构建） */
.player-card{
    background:rgba(255,255,255,.10);
    border:1px solid rgba(255,255,255,.18);
    border-radius:var(--radius-card);
    padding:20px;
    backdrop-filter:blur(6px);
    max-width:420px;
    margin:0 auto;
}
.player-head{display:flex;align-items:center;gap:12px}
.player-cover{
    width:52px;height:52px;
    flex:0 0 auto;
    border-radius:var(--radius-btn);
    background:linear-gradient(135deg,#007cc2,#052953);
    color:#fff;
    display:flex;align-items:center;justify-content:center;
    font-size:22px;
}
.player-meta{flex:1 1 auto;min-width:0}
.player-title{margin:0;font-size:15px;font-weight:600;color:#fff;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.player-artist{margin:0;font-size:12.5px;color:rgba(255,255,255,.7);white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.icon-btn{
    flex:0 0 auto;
    display:inline-flex;align-items:center;justify-content:center;
    width:36px;height:36px;padding:0;
    background:transparent;
    border:0;border-radius:50%;
    color:rgba(255,255,255,.85);
    cursor:pointer;
}
.icon-btn svg{width:19px;height:19px}
.icon-btn:hover,.icon-btn:focus-visible{background:rgba(255,255,255,.14);color:#fff}
.icon-btn.is-active{color:var(--accent)}
.player-progress{margin:16px 0 10px}
.player-bar{height:4px;border-radius:var(--radius-pill);background:rgba(255,255,255,.22);overflow:hidden}
.player-fill{display:block;height:100%;width:38%;border-radius:var(--radius-pill);background:var(--accent);transition:width .5s linear}
.player-time{display:flex;justify-content:space-between;font-size:12px;color:rgba(255,255,255,.7);margin-top:6px}
.player-controls{display:flex;align-items:center;gap:10px}
.player-controls .play-btn{
    width:44px;height:44px;
    background:#fff;color:var(--primary);
}
.player-controls .play-btn:hover{background:var(--accent);color:#fff}
.play-btn .icon-pause{display:none}
.play-btn.is-active .icon-play{display:none}
.play-btn.is-active .icon-pause{display:inline-block}
.volume{display:flex;align-items:center;gap:8px;margin-left:auto;color:rgba(255,255,255,.85)}
.volume svg{width:18px;height:18px}
.volume input[type=range]{width:72px;accent-color:var(--accent)}

/* 3 组歌单卡片切换标签 */
.playlist{max-width:420px;margin:16px auto 0}
.tab-btns{display:flex;flex-wrap:wrap;gap:8px;margin-bottom:10px}
.tab-btn{
    padding:6px 14px;
    font-family:inherit;font-size:13.5px;font-weight:600;
    color:rgba(255,255,255,.85);
    background:rgba(255,255,255,.10);
    border:1px solid rgba(255,255,255,.18);
    border-radius:var(--radius-pill);
    cursor:pointer;
}
.tab-btn.is-active,.tab-btn:hover{background:#fff;color:var(--primary);border-color:#fff}
.playlist-panel{border-radius:var(--radius-card);overflow:hidden}
.playlist-row{
    display:flex;align-items:center;gap:10px;
    padding:9px 12px;
    font-size:13.5px;
    color:rgba(255,255,255,.9);
    background:rgba(255,255,255,.06);
    border-bottom:1px solid rgba(255,255,255,.08);
}
.playlist-row:last-child{border-bottom:0}
.playlist-row .rank{width:18px;color:var(--accent);font-weight:700}
.playlist-row .name{flex:1 1 auto;min-width:0;white-space:nowrap;overflow:hidden;text-overflow:ellipsis}
.playlist-row .dur{color:rgba(255,255,255,.6);font-size:12.5px}
html.js .playlist-panel{display:none}
html.js .playlist-panel.is-active{display:block}

/* ============================================================
   2.3 公告栏 / 更新提示条
   ============================================================ */
.notice{
    background:rgba(5,41,83,.10);      /* 主色 10% 透明度 */
    border-left:4px solid var(--accent);
}
.notice .container{
    display:flex;flex-wrap:wrap;align-items:center;gap:8px 12px;
    padding-top:14px;padding-bottom:14px;
}
.notice h2{font-size:16px;font-weight:600;margin:0;flex:1 1 260px}
.notice .notice-link{font-size:14px;font-weight:600;color:var(--primary);white-space:nowrap}
.notice .notice-link:hover{color:var(--primary-light)}

/* ============================================================
   2.4 核心功能展示区
   ============================================================ */
.card-grid{display:grid;gap:16px}
.feature-card{
    background:var(--bg-alt);
    border-radius:var(--radius-card);
    padding:20px;               /* 移动端卡片内边距 */
    box-shadow:var(--shadow-sm);
}
.feature-card .icon{font-size:24px;line-height:1;display:block;margin-bottom:10px}
.feature-card h3{margin-bottom:8px}
.feature-card p{color:var(--text-sub);margin-bottom:10px}
.card-link{font-size:14px;font-weight:600;color:var(--primary-light)}
.card-link:hover{color:var(--primary)}

/* ============================================================
   2.5 同类产品对比表（移动端横向滚动）
   ============================================================ */
.table-scroll{overflow-x:auto;-webkit-overflow-scrolling:touch;border-radius:var(--radius-card);background:#fff}
.compare-table{min-width:600px;font-size:14px;background:#fff}
.compare-table th,.compare-table td{padding:12px 14px;text-align:left;border-bottom:1px solid #e6ebf2}
.compare-table thead th{background:var(--primary);color:#fff;font-weight:600;white-space:nowrap}
.compare-table tbody th{background:var(--bg-alt);color:var(--text);font-weight:600;white-space:nowrap;position:sticky;left:0}
.compare-table tbody tr:nth-child(even) td{background:#fafbfd}
.compare-table td{color:var(--text-sub)}
.compare-table td.is-self{color:var(--primary);font-weight:600}
.table-hint{font-size:13px;color:var(--text-muted);margin-top:8px}

/* ============================================================
   2.6 最新资讯区
   ============================================================ */
.news-card{
    background:#fff;
    border:1px solid #e9eef5;
    border-radius:var(--radius-card);
    overflow:hidden;
    display:flex;flex-direction:column;
    height:100%;
}
.news-card .thumb{aspect-ratio:16 / 9;width:100%;height:auto;object-fit:cover;border-radius:0;background:var(--bg-alt)}
.news-card .body{padding:18px;display:flex;flex-direction:column;flex:1 1 auto}
.news-card h3{margin-bottom:8px}
.news-card p{color:var(--text-sub);flex:1 1 auto;margin-bottom:10px}
.news-card .meta{font-size:13px;color:var(--text-muted);margin-bottom:8px}

/* ============================================================
   2.7 用户评价区
   ============================================================ */
.review-card{
    background:var(--bg-alt);
    border-radius:var(--radius-card);
    padding:20px;
    box-shadow:var(--shadow-sm);
    display:flex;flex-direction:column;height:100%;
}
.stars{color:var(--accent);font-size:15px;letter-spacing:2px;margin-bottom:10px}
.review-card blockquote{margin:0 0 14px;color:var(--text-sub);flex:1 1 auto}
.review-user{display:flex;align-items:center;gap:10px}
.avatar{width:40px;height:40px;border-radius:50%;flex:0 0 auto;background:linear-gradient(135deg,#007cc2,#052953)}
.review-user .name{font-size:14px;font-weight:600;margin:0}
.review-user .tag{font-size:12.5px;color:var(--text-muted);margin:0}

/* ============================================================
   2.8 FAQ 常见问题区（手风琴）
   无 JS 时默认展开
   ============================================================ */
.faq{max-width:100%;margin:0 auto}
.faq-item{
    background:#fff;
    border:1px solid #e9eef5;
    border-radius:var(--radius-card);
    margin-bottom:12px;
    overflow:hidden;
}
.faq-item summary{
    cursor:pointer;
    padding:16px 44px 16px 18px;
    font-size:16px;font-weight:600;
    position:relative;
    list-style:none;
}
.faq-item summary::-webkit-details-marker{display:none}
.faq-item summary::after{
    content:"+";
    position:absolute;right:18px;top:50%;transform:translateY(-50%);
    font-size:20px;font-weight:400;color:var(--primary-light);
}
.faq-item[open] summary::after{content:"–"}
.faq-item[open] summary{color:var(--primary)}
.faq-item summary h3{display:inline;font-size:inherit;font-weight:inherit;margin:0;color:inherit}
.faq-answer{padding:0 18px 16px;color:var(--text-sub)}
.faq-answer p{margin:0}

/* ============================================================
   2.9 底部下载 / 转化区
   ============================================================ */
.cta-banner{background:linear-gradient(135deg,#052953,#007cc2);color:#fff;padding:48px 0}
.cta-banner h2{color:#fff}
.cta-banner p{color:rgba(255,255,255,.82);margin-bottom:0}
.cta-banner .cta-inner{display:flex;flex-direction:column;gap:20px}
.cta-fallback{font-size:13px;color:rgba(255,255,255,.8);margin-top:10px}

/* ============================================================
   2.10 Footer
   ============================================================ */
.site-footer{background:var(--primary);color:rgba(255,255,255,.75);padding:40px 0 20px;font-size:14px}
.footer-grid{display:grid;gap:24px;grid-template-columns:1fr}
.site-footer h2,.site-footer h3{color:#fff;font-size:15px;font-weight:600;margin-bottom:10px}
.site-footer a{color:rgba(255,255,255,.75)}
.site-footer a:hover{color:#fff}
.footer-brand{display:flex;align-items:center;gap:8px;color:#fff;font-weight:700;font-size:17px;margin-bottom:8px}
.footer-brand img{width:26px;height:26px;border-radius:50%}
.footer-links li{margin-bottom:6px}
.social{display:flex;flex-wrap:wrap;gap:10px}
.social li{display:inline-block}
.social a{
    display:inline-block;
    padding:4px 12px;
    border:1px solid rgba(255,255,255,.25);
    border-radius:var(--radius-pill);
    font-size:13px;
}
.social a:hover{background:rgba(255,255,255,.12);text-decoration:none}
.footer-bottom{
    border-top:1px solid rgba(255,255,255,.15);
    margin-top:24px;padding-top:16px;
    display:flex;flex-wrap:wrap;gap:8px;justify-content:space-between;
    font-size:13px;color:rgba(255,255,255,.6);
}

/* ============================================================
   子页面通用样式
   ============================================================ */
.page-head{background:var(--bg-alt);padding:32px 0;border-bottom:1px solid #e9eef5}
.page-head h1{margin-bottom:8px}
.page-head p{color:var(--text-sub);margin:0;max-width:70ch}
.breadcrumb{font-size:13px;color:var(--text-muted);margin-bottom:10px}
.breadcrumb a{color:var(--text-sub)}
.article{max-width:840px}
.article h2{margin-top:28px}
.article ul{list-style:disc;padding-left:22px;color:var(--text-sub);margin-bottom:12px}
.article ul li{margin-bottom:6px}
.article-meta{font-size:13px;color:var(--text-muted);margin-bottom:16px}
.list-stack{display:grid;gap:16px}
.list-title{margin-top:32px}

/* ============================================================
   5.2 响应式断点
   ============================================================ */
/* 平板 / 小桌面 */
@media (min-width:768px){
    body{font-size:16px}
    :root{--section-py:64px}
    .nav-toggle{display:none}
    .nav-container{min-height:64px}
    .nav-panel{
        position:static;
        display:block;
        padding:0;
        border:0;box-shadow:none;
        background:transparent;
        max-width:none;
    }
    html.js .nav-panel{display:block}
    .nav-panel .nav-menu li{display:inline-block;margin:0 10px}
    .nav-panel .nav-menu a{display:inline-block;padding:6px 2px;border-bottom:0}
    .nav-panel .nav-cta-wrap{margin-top:0}
    .nav-panel .nav-cta{display:inline-block;width:auto}
    .nav-inner{display:flex;align-items:center;gap:12px}
    .card-grid{grid-template-columns:repeat(2,1fr);gap:20px}
    .news-grid,.review-grid{display:grid;grid-template-columns:repeat(2,1fr);gap:20px}
    .feature-card,.review-card{padding:24px}
    .footer-grid{grid-template-columns:repeat(2,1fr)}
    .hero{padding:64px 0}
    .hero-stats li{min-width:auto;flex:1 1 0}
    .faq{max-width:760px}
}
/* 桌面端 */
@media (min-width:1024px){
    body{font-size:16px}
    :root{--section-py:88px}
    h1{font-size:40px}
    h2{font-size:28px}
    h3{font-size:20px}
    .hero{padding:100px 0}
    .hero-inner{display:grid;grid-template-columns:57% 43%;align-items:center;gap:40px}
    .hero-stats{display:flex}
    .hero-stats strong{font-size:26px}
    .player-card{margin:0 0 0 auto}
    .playlist{margin:16px 0 0 auto}
    .card-grid{grid-template-columns:repeat(3,1fr);gap:24px}
    .news-grid,.review-grid{grid-template-columns:repeat(3,1fr);gap:24px}
    .feature-card,.review-card,.news-card .body{padding:28px}
    .footer-grid{grid-template-columns:1.4fr 1fr 1fr 1fr;gap:32px}
    .cta-banner{padding:80px 0}
    .cta-banner .cta-inner{flex-direction:row;align-items:center;justify-content:space-between;gap:40px}
    .cta-banner .cta-text{flex:1 1 60%}
    .notice h2{font-size:18px}
    .section-head{margin-bottom:32px}
    .faq{max-width:840px}
}