:root{
  --primary:#2563eb; --primary-dark:#1d4ed8; --primary-soft:#eff4ff;
  --ink:#0f172a; --ink-2:#334155; --ink-3:#64748b; --line:#e5e9f2;
  --bg:#f4f6fb; --card:#ffffff; --sidebar:#0f172a; --sidebar-2:#1e293b;
  --emerald:#059669; --amber:#d97706; --rose:#e11d48; --violet:#7c3aed;
  --code-bg:#0f1b33; --radius:14px; --shadow:0 1px 2px rgba(15,23,42,.05),0 8px 24px -12px rgba(15,23,42,.12);
}
*{box-sizing:border-box;margin:0;padding:0}
html{scroll-behavior:smooth}
body{font-family:"PingFang SC","Microsoft YaHei","Segoe UI",system-ui,-apple-system,sans-serif;
     background:var(--bg);color:var(--ink);font-size:15px;line-height:1.7;-webkit-font-smoothing:antialiased}
code,pre{font-family:"JetBrains Mono","Cascadia Code",Consolas,"Courier New",monospace}
a{text-decoration:none;color:inherit}

/* ---------- Header ---------- */
.topbar{position:sticky;top:0;z-index:50;background:rgba(255,255,255,.88);backdrop-filter:blur(12px);
  border-bottom:1px solid var(--line);display:flex;align-items:center;gap:16px;padding:0 24px;height:64px}
.brand{display:flex;align-items:center;gap:11px}
.brand-logo{width:36px;height:36px;border-radius:10px;background:linear-gradient(135deg,#2563eb,#7c3aed);
  display:grid;place-items:center;color:#fff;font-weight:800;font-size:15px;letter-spacing:-.5px;box-shadow:0 4px 10px -2px rgba(37,99,235,.5)}
.brand h1{font-size:16.5px;font-weight:700;line-height:1.2;white-space:nowrap}
.brand small{display:block;font-size:11.5px;color:var(--ink-3);font-weight:500;letter-spacing:.3px}
.search-wrap{flex:1;max-width:520px;position:relative}
.search-wrap svg{position:absolute;left:13px;top:50%;transform:translateY(-50%);color:var(--ink-3);width:17px;height:17px}
#search{width:100%;height:40px;border:1px solid var(--line);border-radius:10px;background:#f8fafc;
  padding:0 14px 0 40px;font-size:14px;color:var(--ink);outline:none;transition:.2s}
#search:focus{border-color:var(--primary);background:#fff;box-shadow:0 0 0 3px rgba(37,99,235,.12)}
.top-actions{display:flex;align-items:center;gap:8px;margin-left:auto}
.btn{display:inline-flex;align-items:center;gap:6px;height:38px;padding:0 14px;border:1px solid var(--line);
  background:#fff;border-radius:10px;color:var(--ink-2);font-size:13.5px;font-weight:600;cursor:pointer;transition:.18s;white-space:nowrap}
.btn:hover{border-color:var(--primary);color:var(--primary);background:var(--primary-soft)}
.btn svg{width:16px;height:16px}
#menuBtn{display:none}

/* ---------- Layout ---------- */
.layout{display:flex;align-items:flex-start;max-width:1380px;margin:0 auto}
.sidebar{width:248px;flex:none;position:sticky;top:64px;height:calc(100vh - 64px);overflow-y:auto;
  padding:22px 14px;background:var(--sidebar);color:#cbd5e1}
.side-title{font-size:11px;letter-spacing:1.5px;color:#64748b;font-weight:700;padding:0 12px 10px}
.nav-item{display:flex;align-items:center;gap:10px;width:100%;padding:9px 12px;border-radius:9px;border:none;
  background:transparent;color:#cbd5e1;font-size:13.5px;font-weight:600;cursor:pointer;text-align:left;transition:.15s;margin-bottom:2px}
.nav-item:hover{background:var(--sidebar-2);color:#fff}
.nav-item.active{background:linear-gradient(90deg,rgba(37,99,235,.9),rgba(37,99,235,.55));color:#fff;box-shadow:0 4px 12px -4px rgba(37,99,235,.7)}
.nav-item .nav-ico{font-size:15px;width:18px;text-align:center}
.nav-name{flex:1;overflow:hidden;text-overflow:ellipsis;white-space:nowrap}
.nav-count{font-size:11px;background:rgba(148,163,184,.18);padding:1px 8px;border-radius:20px;color:#94a3b8;font-weight:700}
.nav-item.active .nav-count{background:rgba(255,255,255,.22);color:#fff}
.side-progress{margin:16px 12px 0;padding-top:14px;border-top:1px solid #1e293b}
.side-progress .bar{height:6px;border-radius:6px;background:#1e293b;overflow:hidden}
.side-progress .bar i{display:block;height:100%;width:0;background:linear-gradient(90deg,#3b82f6,#22d3ee);transition:width .3s}
.side-progress p{font-size:12px;color:#94a3b8;margin-top:8px;text-align:center}

/* ---------- Main ---------- */
.main{flex:1;min-width:0;padding:28px 32px 80px}
.hero{background:linear-gradient(120deg,#1e3a8a 0%,#2563eb 55%,#4f46e5 100%);border-radius:18px;padding:28px 30px;color:#fff;
  margin-bottom:26px;position:relative;overflow:hidden;box-shadow:0 16px 40px -18px rgba(37,99,235,.55)}
.hero::after{content:"";position:absolute;right:-60px;top:-60px;width:240px;height:240px;border-radius:50%;
  background:radial-gradient(circle,rgba(255,255,255,.16),transparent 70%)}
.hero h2{font-size:23px;font-weight:800;margin-bottom:7px;letter-spacing:.3px}
.hero p{opacity:.88;font-size:14px;max-width:680px}
.hero .tags{display:flex;gap:8px;margin-top:15px;flex-wrap:wrap}
.hero .tags span{font-size:12px;background:rgba(255,255,255,.16);border:1px solid rgba(255,255,255,.25);
  padding:3px 12px;border-radius:20px;font-weight:600}
.crumb{font-size:13px;color:var(--ink-3);margin-bottom:14px;display:flex;align-items:center;gap:7px;flex-wrap:wrap}
.crumb a{color:var(--primary);font-weight:600}
.crumb a:hover{text-decoration:underline}
.result-tip{display:none;font-size:13px;color:var(--ink-3);margin-bottom:14px;padding:10px 14px;background:#fff;
  border:1px dashed var(--line);border-radius:10px}
.result-tip b{color:var(--primary)}

/* ---------- 首页分类卡片 ---------- */
.cat-grid{display:grid;grid-template-columns:repeat(auto-fill,minmax(268px,1fr));gap:16px}
.cat-card{display:block;background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:20px;
  box-shadow:var(--shadow);transition:.2s;cursor:pointer}
.cat-card:hover{border-color:var(--primary);transform:translateY(-3px);box-shadow:0 18px 34px -18px rgba(37,99,235,.45)}
.cat-card-top{display:flex;align-items:center;gap:12px;margin-bottom:14px}
.cat-card-ico{width:44px;height:44px;border-radius:12px;display:grid;place-items:center;font-size:22px;flex:none}
.cat-card-top h3{font-size:16.5px;font-weight:800;flex:1}
.cat-card-cnt{font-size:12px;color:var(--ink-3);font-weight:700;background:#f1f5fb;padding:2px 10px;border-radius:20px}
.cat-card .bar{height:7px;border-radius:7px;background:#eef2f8;overflow:hidden;margin:4px 0 10px}
.cat-card .bar i{display:block;height:100%;width:0;background:linear-gradient(90deg,#2563eb,#22d3ee);transition:width .4s}
.cat-card-meta{display:flex;justify-content:space-between;font-size:12.5px;color:var(--ink-3);font-weight:600}
.cat-card-meta b{color:var(--ink-2)}
.cat-dist{display:flex;gap:6px;margin-top:12px;flex-wrap:wrap}
.cat-dist span{font-size:11.5px;font-weight:700;padding:2px 9px;border-radius:20px;background:#f1f5fb;color:var(--ink-3)}
.cat-dist span.on{color:#fff}
.d0{background:#f1f5fb}.d0.on{background:#e11d48}
.d1.on{background:#d97706}.d2.on{background:#2563eb}.d3.on{background:#059669}

/* ---------- 题目卡片 ---------- */
.cat-section{margin-bottom:38px;scroll-margin-top:84px}
.cat-head{display:flex;align-items:center;gap:12px;margin:6px 0 16px}
.cat-icon{width:38px;height:38px;border-radius:11px;display:grid;place-items:center;font-size:19px;flex:none}
.cat-head h3{font-size:19px;font-weight:800}
.cat-head .cnt{font-size:12.5px;color:var(--ink-3);font-weight:600;background:#fff;border:1px solid var(--line);
  padding:2px 11px;border-radius:20px}
.q-card{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:18px 20px;
  margin-bottom:13px;box-shadow:var(--shadow);transition:border-color .2s,box-shadow .2s}
.q-card:hover{border-color:#c7d5ef}
.q-card.open{border-color:#bcd0f2}
.q-top{display:flex;gap:13px;align-items:flex-start}
.q-no{flex:none;min-width:34px;height:24px;padding:0 7px;border-radius:7px;background:var(--primary-soft);color:var(--primary-dark);
  font-size:12px;font-weight:800;display:grid;place-items:center;margin-top:2px}
.q-title{flex:1;font-size:15.5px;font-weight:700;color:var(--ink);line-height:1.55}
.badge{display:inline-block;font-size:11px;font-weight:700;padding:1px 9px;border-radius:20px;margin-left:8px;vertical-align:1px}
.badge.l1{background:#ecfdf5;color:var(--emerald)}
.badge.l2{background:#fffbeb;color:var(--amber)}
.badge.l3{background:#fff1f4;color:var(--rose)}
.eye-btn{flex:none;width:38px;height:38px;border-radius:10px;border:1px solid var(--line);background:#fff;cursor:pointer;
  display:grid;place-items:center;color:var(--ink-3);transition:.18s;margin-left:6px}
.eye-btn:hover{color:var(--primary);border-color:var(--primary);background:var(--primary-soft);transform:translateY(-1px)}
.eye-btn .icon-eye-off{display:none}
.q-card.open .eye-btn{color:#fff;background:var(--primary);border-color:var(--primary)}
.q-card.open .eye-btn .icon-eye{display:none}
.q-card.open .eye-btn .icon-eye-off{display:block}
.eye-btn svg{width:19px;height:19px}

/* ---------- 熟知度标签 ---------- */
.q-fam{display:flex;align-items:center;gap:7px;flex-wrap:wrap;margin:11px 0 0 47px}
.q-fam .fam-label{font-size:12px;color:var(--ink-3);font-weight:700;margin-right:1px}
.fam-btn{height:26px;padding:0 12px;border-radius:20px;border:1px solid var(--line);background:#fff;color:var(--ink-3);
  font-size:12px;font-weight:700;cursor:pointer;transition:.16s}
.fam-btn:hover{border-color:#94a3b8;color:var(--ink-2)}
.fam-btn[data-v="0"].on{background:#e11d48;border-color:#e11d48;color:#fff}
.fam-btn[data-v="1"].on{background:#d97706;border-color:#d97706;color:#fff}
.fam-btn[data-v="2"].on{background:#2563eb;border-color:#2563eb;color:#fff}
.fam-btn[data-v="3"].on{background:#059669;border-color:#059669;color:#fff}
.q-fam .fam-clear{font-size:11.5px;color:#94a3b8;background:none;border:none;cursor:pointer;font-weight:600;display:none}
.q-fam.marked .fam-clear{display:inline-block}
.q-fam .fam-clear:hover{color:var(--rose)}

.answer-wrap{display:grid;grid-template-rows:0fr;transition:grid-template-rows .32s cubic-bezier(.4,0,.2,1)}
.q-card.open .answer-wrap{grid-template-rows:1fr}
.answer-inner{overflow:hidden;min-height:0}
.answer{border-top:1px dashed var(--line);margin-top:15px;padding-top:16px;color:var(--ink-2);font-size:14.2px}
.answer h4{font-size:14.5px;color:var(--primary-dark);margin:16px 0 7px;font-weight:800;display:flex;align-items:center;gap:7px}
.answer h4::before{content:"";width:4px;height:15px;border-radius:2px;background:var(--primary);display:inline-block}
.answer h4:first-child{margin-top:4px}
.answer p{margin:8px 0}
.answer ul,.answer ol{margin:8px 0 8px 4px;padding-left:22px}
.answer li{margin:4px 0}
.answer strong{color:var(--ink);font-weight:700}
.answer code.inline{background:#eef2f8;color:#be185d;border-radius:5px;padding:1px 6px;font-size:12.8px}
.answer blockquote{margin:10px 0;padding:10px 14px;background:#fffbeb;border-left:3px solid var(--amber);
  border-radius:0 8px 8px 0;color:#92400e;font-size:13.5px}
.answer table{width:100%;border-collapse:collapse;margin:12px 0;font-size:13.3px;display:block;overflow-x:auto}
.answer th,.answer td{border:1px solid var(--line);padding:8px 12px;text-align:left;vertical-align:top}
.answer th{background:#f1f5fb;color:var(--ink);font-weight:700;white-space:nowrap}
.answer tr:nth-child(even) td{background:#fafbfe}
.code-block{margin:12px 0;border-radius:10px;overflow:hidden;background:var(--code-bg)}
.code-bar{display:flex;align-items:center;justify-content:space-between;padding:6px 14px;background:rgba(255,255,255,.06);
  border-bottom:1px solid rgba(255,255,255,.08)}
.code-lang{font-size:11.5px;color:#93c5fd;font-weight:700;letter-spacing:.6px;text-transform:uppercase}
.copy-btn{font-size:11.5px;color:#94a3b8;background:transparent;border:none;cursor:pointer;font-weight:600;
  display:flex;align-items:center;gap:4px;border-radius:6px;padding:3px 8px;transition:.15s}
.copy-btn:hover{color:#fff;background:rgba(255,255,255,.1)}
.copy-btn svg{width:13px;height:13px}
.code-block pre{padding:14px 16px;overflow-x:auto;color:#dbe7ff;font-size:13px;line-height:1.65}
mark{background:#fef08a;color:inherit;border-radius:3px;padding:0 2px}
.no-result{display:none;text-align:center;padding:70px 20px;color:var(--ink-3)}
.no-result svg{width:54px;height:54px;margin-bottom:14px;opacity:.5}

/* ---------- 初始空态 ---------- */
.empty-state{background:var(--card);border:1px solid var(--line);border-radius:var(--radius);padding:46px 30px;
  text-align:center;box-shadow:var(--shadow)}
.empty-ico{font-size:46px;line-height:1;margin-bottom:16px}
.empty-state h3{font-size:19px;font-weight:800;margin-bottom:9px}
.empty-state p{font-size:14px;color:var(--ink-3);max-width:560px;margin:0 auto 22px}
.empty-chips{display:flex;flex-wrap:wrap;gap:10px;justify-content:center}
.empty-chip{display:inline-flex;align-items:center;gap:9px;background:#f6f8fc;border:1px solid var(--line);
  border-radius:20px;padding:6px 14px}
.empty-chip b{font-size:13px;font-weight:700;color:var(--ink-2)}
.empty-chip i{font-size:12px;font-style:normal;font-weight:700;color:var(--primary);background:var(--primary-soft);
  padding:1px 9px;border-radius:20px}

#backTop{position:fixed;right:26px;bottom:28px;width:44px;height:44px;border-radius:50%;border:none;cursor:pointer;
  background:var(--primary);color:#fff;display:grid;place-items:center;box-shadow:0 8px 20px -6px rgba(37,99,235,.6);
  opacity:0;pointer-events:none;transform:translateY(10px);transition:.25s;z-index:60}
#backTop.show{opacity:1;pointer-events:auto;transform:translateY(0)}
#backTop svg{width:20px;height:20px}
.mask{display:none;position:fixed;inset:0;background:rgba(15,23,42,.45);z-index:40}

@media (max-width: 960px){
  .brand h1{font-size:15px} .brand small{display:none}
  #menuBtn{display:inline-flex}
  .sidebar{position:fixed;left:0;top:64px;z-index:45;transform:translateX(-100%);transition:transform .25s;height:calc(100vh - 64px)}
  .sidebar.open{transform:translateX(0)}
  .mask.show{display:block}
  .main{padding:20px 14px 70px}
  .topbar{padding:0 14px;gap:10px}
  .btn .btn-text{display:none} .btn{padding:0 10px}
  .hero{padding:22px 20px} .hero h2{font-size:19px}
  .q-fam{margin-left:0}
}