:root{
    --bg:#f5f6f8;--card:#fff;--line:#e4e7eb;--ink:#1b1f24;--muted:#6b7280;
    --blue:#2563eb;--blue-soft:#eef4ff;--green:#0f7b53;--green-soft:#eaf7f1;
    --red:#c0392b;--red-soft:#fdecea;--amber:#b45309;--amber-soft:#fdf6e8;
  }
  *{box-sizing:border-box;-webkit-tap-highlight-color:transparent}
  body{margin:0;background:var(--bg);color:var(--ink);font-size:15px;line-height:1.65;
    font-family:-apple-system,BlinkMacSystemFont,"PingFang SC","Hiragino Sans GB","Microsoft YaHei",system-ui,sans-serif;}
  .wrap{max-width:880px;margin:0 auto;padding:26px 18px 70px}
  h1{font-size:21px;font-weight:600;margin:0 0 6px;letter-spacing:.2px}
  h2{font-size:16px;font-weight:600;margin:0 0 10px}
  h3{font-size:14px;font-weight:600;margin:0 0 8px;color:var(--ink)}
  .sub{color:var(--muted);font-size:13px;margin:0 0 20px}
  .card{background:var(--card);border:1px solid var(--line);border-radius:14px;padding:18px 20px;margin-bottom:13px}
  .grid2{display:grid;grid-template-columns:1fr 1fr;gap:13px}
  @media(max-width:640px){.grid2{grid-template-columns:1fr}}
  .mod{cursor:pointer;transition:border-color .15s,box-shadow .15s}
  .mod:hover{border-color:#b9c6dd;box-shadow:0 2px 10px rgba(20,40,80,.06)}
  .mod .tag{display:inline-block;font-size:11px;padding:2px 8px;border-radius:20px;background:var(--blue-soft);color:var(--blue);margin-right:6px}
  .mod p{font-size:12.5px;color:var(--muted);margin:8px 0 0;line-height:1.6}
  .modlink{margin:12px 0 0;font-size:12.5px;line-height:1.4}
  .modlink span{color:var(--blue);cursor:pointer;border-bottom:1px dashed rgba(37,99,235,.45);padding-bottom:1px}
  .modlink span:hover{color:#1d4fd8}
  .simcard{border-left:3px solid var(--blue)}
  .btn{display:inline-block;border:1px solid var(--line);background:#fff;color:var(--ink);
    padding:9px 18px;border-radius:9px;font-size:14px;cursor:pointer;font-family:inherit}
  .btn:hover{background:#f8f9fb}
  .btn.primary{background:var(--blue);border-color:var(--blue);color:#fff}
  .btn.primary:hover{background:#1d4fd8}
  .bar{display:flex;align-items:center;justify-content:space-between;margin-bottom:16px;gap:12px;flex-wrap:wrap}
  .clock{font-variant-numeric:tabular-nums;font-size:15px;font-weight:600;color:var(--ink)}
  .clock.warn{color:var(--red)}
  .prog{font-size:13px;color:var(--muted)}
  .matrix{display:grid;grid-template-columns:repeat(3,72px);gap:7px;justify-content:center;margin:18px 0}
  .mcell{width:72px;height:72px;display:flex;align-items:center;justify-content:center;
    border:1px solid var(--line);border-radius:9px;background:#fff}
  .mcell.mq{background:#f2f4f7;color:#9aa3af;font-size:24px;font-weight:600}
  .opts{display:grid;gap:9px;justify-content:center;margin:0}
  .opts.g3{grid-template-columns:repeat(3,88px)}
  .opts.g2{grid-template-columns:repeat(2,minmax(140px,1fr))}
  .opts.g4{grid-template-columns:repeat(2,132px)}
  .answer-zone{border-top:1px dashed #cfd6e0;margin-top:22px;padding-top:14px}
  .zone-label{font-size:12px;color:var(--muted);text-align:center;margin-bottom:11px;letter-spacing:1px}
  .opt{display:flex;align-items:center;justify-content:center;border:1.5px solid var(--line);
    background:#fff;border-radius:11px;padding:8px;cursor:pointer;font-family:inherit;font-size:14px;
    color:var(--ink);min-height:56px;transition:border-color .12s,background .12s}
  .opt:hover{border-color:#9fb3d4;background:#fafbfd}
  .opt.ok{border-color:var(--green);background:var(--green-soft)}
  .opt.no{border-color:var(--red);background:var(--red-soft)}
  .opt[disabled]{cursor:default}
  .qtxt{font-size:15.5px;line-height:1.75;margin:6px 0 4px}
  .hint{font-size:12.5px;color:var(--muted);margin-top:10px}
  .foldrow{display:flex;gap:26px;align-items:center;justify-content:center;margin:16px 0;flex-wrap:wrap}
  .grid5{margin:16px auto;display:block}
  .stat{display:flex;gap:28px;flex-wrap:wrap;margin:6px 0 4px}
  .stat div{font-size:13px;color:var(--muted)}
  .stat b{display:block;font-size:26px;font-weight:600;color:var(--ink);line-height:1.2;font-variant-numeric:tabular-nums}
  .note{background:var(--amber-soft);border:1px solid #f0e0bd;border-radius:11px;padding:13px 15px;font-size:13px;color:#6b4a0f}
  .note b{color:var(--amber)}
  .kv{font-size:13.5px;margin:0}
  .kv li{margin-bottom:7px}
  code{background:#eef1f5;padding:1px 5px;border-radius:4px;font-size:12.5px;
    font-family:ui-monospace,SFMono-Regular,Menlo,monospace}
  .footer{text-align:center;color:#9aa3af;font-size:12px;margin-top:26px}
  .prep-head{display:flex;justify-content:space-between;align-items:baseline;gap:12px;flex-wrap:wrap}
  .prep-list{display:grid;gap:9px;margin:14px 0}
  .prep-item{display:flex;align-items:flex-start;gap:10px;padding:10px 12px;border:1px solid var(--line);border-radius:9px;cursor:pointer}
  .prep-item input{width:18px;height:18px;margin:3px 0 0;accent-color:var(--blue);flex:none}
  .sources a{color:var(--blue);overflow-wrap:anywhere}
  details summary{cursor:pointer;font-weight:600}
  .site-header{display:flex;align-items:center;justify-content:space-between;gap:16px;flex-wrap:wrap;margin-bottom:26px}
  .brand{font-weight:700;color:var(--ink);text-decoration:none;font-size:16px}
  .nav{display:flex;gap:6px;flex-wrap:wrap}.nav a{color:var(--muted);text-decoration:none;padding:8px 12px;border-radius:9px;font-size:14px}.nav a.active{background:var(--blue-soft);color:var(--blue);font-weight:600}
  .hero{padding:25px;background:#eaf1ff;border:1px solid #dae6ff;border-radius:16px;margin-bottom:18px}.hero h1{font-size:26px;margin-bottom:7px}.hero p{margin:0;color:#516582}
  .section-title{margin:26px 0 11px}.mod{cursor:default}.mod h2{font-size:17px}.mod .actions{display:flex;gap:8px;flex-wrap:wrap;margin-top:14px}.mod .btn{font-size:13px;padding:8px 12px}.tip{margin:12px 0 0;padding:10px 12px;background:#f5f8fe;border-radius:8px;font-size:13px;color:#3d557b}.steps{display:grid;grid-template-columns:repeat(3,1fr);gap:10px}.step{background:#f7f9fc;border-radius:10px;padding:12px;font-size:13px}.step b{display:block;color:var(--blue);margin-bottom:4px}.review{padding-top:12px;text-align:center;border-top:1px dashed var(--line);margin-top:15px}.review p{margin:4px 0;color:var(--muted);font-size:13px}
  @media(max-width:600px){.steps{grid-template-columns:1fr}.hero h1{font-size:22px}.site-header{margin-bottom:16px}.wrap{padding-top:18px}}
  .backlink{font-size:13px;color:var(--blue);cursor:pointer;text-decoration:none}

/* 页面组件和答题布局 */
.tag-success { background: var(--green-soft); color: var(--green); }
.method-link { margin: 14px 0 0; }
.return-actions { margin-top: 18px; }
.question-progress { margin-top: 4px; }
.fold-hint { margin: 0; max-width: 190px; }
.opts-fold-count { grid-template-columns: repeat(4,1fr); max-width: 430px; margin-left: auto; margin-right: auto; }
.memory-prompt { text-align: center; font-size: 16px; }
.muted-small { color: var(--muted); font-size: 13px; }
.centered { text-align: center; }
.opts-memory-count { grid-template-columns: repeat(4,1fr); max-width: 400px; margin-left: auto; margin-right: auto; }
.opts-memory-sym { grid-template-columns: repeat(2,150px); }
.opts-memory-cell { grid-template-columns: repeat(2,140px); }
.opts-verbal { grid-template-columns: 1fr; }
.no-margin { margin: 0; }
.result-actions { margin-top: 20px; display: flex; gap: 10px; flex-wrap: wrap; }