:root{
  --bg:#f5f7fb; --card:#ffffff; --text:#172033; --muted:#667085;
  --line:#d9e0ec; --primary:#2563eb; --primary2:#1d4ed8;
  --ok:#0f9f6e; --bad:#d92d20; --warn:#f59e0b;
}
*{box-sizing:border-box}
body{margin:0;font-family:-apple-system,BlinkMacSystemFont,"Segoe UI","Microsoft YaHei",Arial,sans-serif;background:var(--bg);color:var(--text)}
.app{display:grid;grid-template-columns:330px 1fr;min-height:100vh}
.sidebar{background:#0f172a;color:#eef2ff;padding:22px;position:sticky;top:0;height:100vh;overflow:auto}
.sidebar-overlay{display:none}
.brand{display:flex;gap:12px;align-items:center;margin-bottom:18px}
.logo{width:46px;height:46px;border-radius:14px;background:linear-gradient(135deg,#60a5fa,#2563eb);display:flex;align-items:center;justify-content:center;font-weight:800}
.brand h1{font-size:18px;margin:0}
.brand p{margin:4px 0 0;color:#aab4cf;font-size:13px}
.stat-grid{display:grid;grid-template-columns:1fr 1fr;gap:10px;margin:18px 0}
.stat{background:#18223a;border:1px solid #26324f;border-radius:14px;padding:12px}
.stat span{display:block;font-size:23px;font-weight:800}
.stat label{color:#aab4cf;font-size:12px}
.panel{border-top:1px solid #25304c;padding-top:16px;margin-top:16px}
.panel h2{font-size:14px;margin:0 0 10px;color:#c7d2fe}
button,select,input{font:inherit}
button{border:1px solid var(--line);background:#fff;color:var(--text);border-radius:10px;padding:10px 12px;cursor:pointer}
button:hover{filter:brightness(.98)}
button.primary{background:var(--primary);border-color:var(--primary);color:#fff}
button.primary:hover{background:var(--primary2)}
button.danger{background:#fff1f0;color:#b42318;border-color:#fecdca}
.icon-btn{width:36px;height:36px;padding:0;display:flex;align-items:center;justify-content:center}
.close-sidebar,.mobile-menu-btn{display:none}
.mode{display:block;width:100%;margin:8px 0;background:#17213a;color:#e5e7eb;border-color:#33405f;text-align:left}
.mode.active{background:#2563eb;border-color:#2563eb;color:#fff}
.panel label{display:block;margin:12px 0 6px;color:#b9c2d8;font-size:13px}
.panel select,.panel input{width:100%;padding:10px;border-radius:10px;border:1px solid #33405f;background:#111a2e;color:#eef2ff}
#importFile{font-size:12px}
#exportWrong,#resetProgress{width:100%;margin-top:10px}
.cloud-status{border:1px solid #33405f;background:#111a2e;color:#cbd5e1;border-radius:10px;padding:10px;line-height:1.45;font-size:12px}
.cloud-status.ok{border-color:#166534;background:#0f2a24;color:#bbf7d0}
.cloud-status.new{border-color:#1d4ed8;background:#10264e;color:#bfdbfe}
.cloud-status.warn{border-color:#92400e;background:#2b2111;color:#fde68a}
.id-actions{display:grid;grid-template-columns:1fr;gap:8px;margin-top:12px}
.id-actions button{width:100%}
.linked-ids{margin-top:12px}
.linked-title{color:#c7d2fe;font-weight:800;font-size:12px;margin-bottom:8px}
.linked-item{display:flex;justify-content:space-between;gap:10px;align-items:center;border:1px solid #33405f;background:#111a2e;border-radius:10px;padding:9px 10px;margin-top:8px;font-size:12px}
.linked-item span{color:#b9c2d8}
.linked-item b{color:#eef2ff;text-align:right;word-break:break-all}
.linked-empty{border:1px dashed #33405f;border-radius:10px;color:#94a3b8;padding:10px;font-size:12px}
.main{padding:28px;min-width:0}
.topbar{display:flex;justify-content:space-between;align-items:center;gap:18px;margin-bottom:18px}
.mode-title{font-size:24px;font-weight:800}
.subtitle{color:var(--muted);margin-top:4px}
.actions{display:flex;gap:10px}
.progress-wrap{display:flex;align-items:center;gap:12px;margin-bottom:18px}
.progress-bar{height:10px;background:#e6ebf5;border-radius:99px;overflow:hidden;flex:1}
#progressInner{height:100%;width:0;background:linear-gradient(90deg,#60a5fa,#2563eb);transition:.2s}
.progress-text{color:var(--muted);font-weight:700;min-width:70px;text-align:right}
.card{background:var(--card);border:1px solid var(--line);border-radius:20px;padding:24px;box-shadow:0 12px 30px rgba(15,23,42,.06)}
.hidden{display:none!important}
.question-meta{display:flex;align-items:center;gap:8px;margin-bottom:12px;flex-wrap:wrap}
.badge{display:inline-flex;background:#e0ecff;color:#1d4ed8;border-radius:999px;padding:5px 10px;font-size:12px;font-weight:700}
.badge.muted{background:#f1f5f9;color:#475569}
.qid{color:var(--muted);font-size:13px;margin-left:auto}
#questionText{font-size:22px;line-height:1.55;margin:10px 0 22px}
.options{display:grid;gap:12px}
.option{border:1px solid var(--line);border-radius:14px;padding:14px;display:flex;gap:12px;align-items:flex-start;cursor:pointer;background:#fff}
.option:hover{border-color:#93b6ff;background:#f8fbff}
.option input{margin-top:4px}
.option-key{font-weight:800;min-width:24px;color:#1d4ed8}
.option span:last-child{min-width:0;word-break:break-word}
.answer-actions{display:flex;gap:10px;flex-wrap:wrap;margin-top:22px}
.result{margin-top:18px;border-radius:14px;padding:14px;border:1px solid var(--line);background:#f8fafc}
.result.correct{background:#ecfdf3;border-color:#abefc6}
.result.wrong{background:#fff1f0;border-color:#fecdca}
.result-title{font-weight:800;margin-bottom:8px}
.explanation{margin-top:10px;line-height:1.7;white-space:normal}
.exam-controls{display:flex;gap:10px;margin:16px 0}
#examSummary{line-height:1.8}
@media (max-width: 860px){
  .app{grid-template-columns:1fr}
  .sidebar{position:relative;height:auto}
  .topbar{align-items:flex-start;flex-direction:column}
}

@media (max-width: 768px){
  body.sidebar-open{overflow:hidden}
  .app{display:block;min-height:100vh}
  .sidebar{
    position:fixed;
    left:0;
    top:0;
    bottom:0;
    width:86vw;
    max-width:360px;
    height:100dvh;
    z-index:120;
    transform:translateX(-105%);
    transition:transform .22s ease;
    box-shadow:20px 0 40px rgba(15,23,42,.28);
    padding:18px;
  }
  body.sidebar-open .sidebar{transform:translateX(0)}
  .sidebar-overlay{
    display:block;
    position:fixed;
    inset:0;
    background:rgba(15,23,42,.45);
    opacity:0;
    pointer-events:none;
    transition:opacity .22s ease;
    z-index:110;
  }
  body.sidebar-open .sidebar-overlay{
    opacity:1;
    pointer-events:auto;
  }
  .close-sidebar{
    display:flex;
    margin-left:auto;
    background:#111a2e;
    color:#eef2ff;
    border-color:#33405f;
    font-size:22px;
    line-height:1;
  }
  .brand{align-items:flex-start}
  .logo{width:40px;height:40px;border-radius:10px;flex:0 0 auto}
  .brand h1{font-size:16px;line-height:1.25}
  .brand p{font-size:12px}
  .stat-grid{grid-template-columns:repeat(4,1fr);gap:6px}
  .stat{padding:8px;text-align:center}
  .stat span{font-size:18px}
  .stat label{font-size:11px}
  .mode{margin:6px 0;padding:9px 10px}
  .main{
    padding:12px;
    padding-bottom:96px;
  }
  .topbar{
    position:sticky;
    top:0;
    z-index:40;
    margin:-12px -12px 12px;
    padding:14px 12px 10px;
    background:rgba(245,247,251,.96);
    border-bottom:1px solid var(--line);
    backdrop-filter:blur(10px);
    gap:10px;
  }
  .mode-title{
    font-size:22px;
    line-height:1.25;
    min-height:28px;
  }
  .subtitle{display:none}
  .actions{
    display:grid;
    grid-template-columns:1fr 1fr 1fr;
    gap:8px;
    width:100%;
    position:static;
    padding:0;
    background:transparent;
    border-top:0;
    box-shadow:none;
  }
  .actions button{min-height:42px;padding:8px}
  .mobile-menu-btn{
    display:block;
    background:#17213a;
    color:#fff;
    border-color:#17213a;
  }
  .progress-wrap{gap:8px;margin-bottom:12px}
  .progress-text{min-width:56px;font-size:13px}
  .card{
    border-radius:12px;
    padding:16px;
    box-shadow:none;
  }
  .question-meta{align-items:flex-start}
  .qid{
    flex-basis:100%;
    margin-left:0;
    word-break:break-all;
  }
  #questionText{
    font-size:18px;
    line-height:1.6;
    margin:10px 0 16px;
    word-break:break-word;
  }
  .options{gap:10px}
  .option{
    min-height:50px;
    padding:13px;
    border-radius:10px;
  }
  .answer-actions{
    position:fixed;
    left:0;
    right:0;
    bottom:0;
    z-index:75;
    display:grid;
    grid-template-columns:1.15fr 1fr 1fr;
    gap:8px;
    margin:0;
    padding:10px 12px calc(10px + env(safe-area-inset-bottom));
    background:#fff;
    border-top:1px solid var(--line);
    box-shadow:0 -8px 24px rgba(15,23,42,.08);
  }
  .answer-actions button{
    min-height:44px;
    padding:9px 8px;
    font-size:14px;
  }
  .result{
    border-radius:10px;
    padding:12px;
    line-height:1.65;
  }
  .exam-controls{display:grid;grid-template-columns:1fr;gap:8px}
}

@media (min-width: 769px) and (max-width: 1100px){
  .app{grid-template-columns:280px 1fr}
  .sidebar{padding:18px}
  .main{padding:22px}
  .card{padding:20px}
  #questionText{font-size:20px}
}