:root{font-family:system-ui,-apple-system,"PingFang SC",sans-serif;color:#0f172a;background:#f6f7f9}
*{box-sizing:border-box}
html{scroll-behavior:smooth}
body{margin:0;padding-top:64px}
a{color:#1d4ed8}
code{background:#f1f5f9;padding:2px 6px;border-radius:6px;font-size:13px;overflow-wrap:anywhere}

/* 顶栏：左品牌，右上角两个按钮（下载电脑端 / 手机看答案） */
.topbar{position:fixed;top:0;left:0;right:0;height:64px;display:flex;align-items:center;justify-content:space-between;gap:12px;padding:0 20px;background:#0f172a;color:#fff;z-index:10}
.brand{display:flex;align-items:center;gap:10px;color:#fff;text-decoration:none;font-weight:700;letter-spacing:.12em;font-size:14px}
.brand .dot{width:9px;height:9px;border-radius:50%;background:#38bdf8;display:inline-block}
.brand-sub{font-weight:500;letter-spacing:0;color:#94a3b8;font-size:13px}
.topbar-actions{display:flex;gap:10px}
.btn{display:inline-block;padding:10px 16px;border-radius:10px;background:#1d4ed8;color:#fff;text-decoration:none;font-weight:600;font-size:14px;white-space:nowrap}
.btn:hover{background:#1e40af}
.btn.ghost{background:#1e293b;color:#cbd5e1}
.btn.ghost:hover{background:#334155}

main{max-width:1100px;margin:0 auto;padding:24px 20px 64px;display:grid;grid-template-columns:200px minmax(0,1fr);gap:32px;align-items:start}

/* 左侧标签目录：桌面粘住，窄屏变横向可滑的 chips */
.toc{position:sticky;top:88px;display:grid;gap:8px}
.toc-title{margin:0 0 4px;font-size:12px;letter-spacing:.18em;color:#94a3b8}
.tag{display:block;padding:8px 12px;border-radius:8px;color:#475569;text-decoration:none;font-size:14px;border:1px solid transparent}
.tag:hover{background:#eef2f7;color:#0f172a}
.tag.active{background:#e8efff;border-color:#c7d7fb;color:#1d4ed8;font-weight:600}

.content{display:grid;gap:16px;min-width:0}
section{background:#fff;border:1px solid #e2e8f0;border-radius:16px;padding:24px}
section:target{border-color:#bfdbfe;box-shadow:0 0 0 3px #eff6ff}
h1{font-size:26px;margin:6px 0 10px;line-height:1.35}
h2{margin:0 0 12px;font-size:19px}
h3{margin:18px 0 6px;font-size:15px;color:#334155}
p{line-height:1.75;font-size:15px;margin:10px 0}
.eyebrow{margin:0;font-size:11px;letter-spacing:.2em;color:#94a3b8}
.lead{color:#475569;font-size:16px;margin-top:0}
.hint{color:#64748b;font-size:13px;line-height:1.7}
.placeholder{color:#94a3b8}
ul,ol{padding-left:20px;line-height:1.8;font-size:15px}
li{margin-bottom:6px}
.feature-grid{list-style:none;padding:0;margin:18px 0 0;display:grid;grid-template-columns:repeat(auto-fit,minmax(200px,1fr));gap:12px}
.feature-grid li{display:grid;gap:4px;padding:14px;border-radius:12px;background:#f8fafc;border:1px solid #eef2f7;margin:0}
.feature-grid strong{font-size:14px}
.feature-grid span{color:#64748b;font-size:13px;line-height:1.6}
.steps li{margin-bottom:12px}
.steps span{display:block;color:#475569;font-size:14px;line-height:1.7}
table{width:100%;border-collapse:collapse;font-size:14px;margin-top:8px}
th,td{padding:10px 8px;border-bottom:1px solid #eef2f7;text-align:left;vertical-align:top}
th{color:#64748b;font-weight:600;font-size:13px}
details{padding:12px 0;border-bottom:1px solid #eef2f7}
details:last-of-type{border-bottom:0}
summary{cursor:pointer;font-weight:600;font-size:15px}
details p{color:#475569;font-size:14px;margin:8px 0 0}
.page-foot{display:flex;flex-wrap:wrap;justify-content:center;text-align:center;gap:8px;color:#94a3b8;font-size:13px;padding:8px 4px}
.page-foot a{color:#64748b}

@media (max-width:860px){
  main{grid-template-columns:1fr;gap:16px;padding-top:12px}
  /* 窄屏时目录变成横向标签条，横向滚动，不占垂直空间 */
  .toc{position:sticky;top:64px;display:flex;gap:8px;overflow-x:auto;padding:10px 2px;background:#f6f7f9;z-index:5}
  .toc-title{display:none}
  .tag{white-space:nowrap;background:#fff;border-color:#e2e8f0}
  .topbar{padding:0 12px}
  .brand-sub{display:none}
  .btn{padding:9px 12px;font-size:13px}
}