:root {
  --primary: #3b5bdb;
  --primary-dk: #2f4ac5;
  --success: #2f9e44;
  --danger: #c92a2a;
  --bg: #f8f9fc;
  --white: #fff;
  --text: #212529;
  --muted: #868e96;
  --border: #dee2e6;
}
*{margin:0;padding:0;box-sizing:border-box}
body{font-family:'Noto Sans KR',-apple-system,sans-serif;background:var(--bg);color:var(--text);font-size:15px;line-height:1.65}
header{background:var(--primary);color:#fff;padding:0 24px;height:54px;display:flex;align-items:center;justify-content:space-between;box-shadow:0 2px 6px rgba(0,0,0,.15)}
header a.logo{color:#fff;text-decoration:none;font-weight:800;font-size:17px}
nav{display:flex;gap:6px}
nav a{color:rgba(255,255,255,.8);text-decoration:none;padding:5px 12px;border-radius:6px;font-size:14px;transition:background .15s}
nav a:hover,nav a.on{background:rgba(255,255,255,.18);color:#fff}
.wrap{max-width:1000px;margin:0 auto;padding:24px 16px}
.card{background:var(--white);border:1px solid var(--border);border-radius:12px;padding:20px;box-shadow:0 1px 4px rgba(0,0,0,.06);margin-bottom:14px}
.q-meta{display:flex;align-items:center;gap:8px;margin-bottom:8px;flex-wrap:wrap}
.q-badge{font-size:11px;font-weight:700;padding:2px 9px;border-radius:99px}
.badge-prog{background:#dbe4ff;color:#2f4ac5}
.badge-db{background:#d3f9d8;color:#2f9e44}
.badge-net{background:#fff3bf;color:#e67700}
.badge-sec{background:#ffe3e3;color:#c92a2a}
.badge-sw{background:#e9ecef;color:#495057}
.badge-os{background:#f3d9fa;color:#862e9c}
.badge-new{background:#fff0f6;color:#a61e4d}
.q-num{font-size:12px;color:var(--muted);font-weight:700}
.q-text{font-size:15px;line-height:1.7;margin-bottom:8px;white-space:pre-wrap}
.q-code{background:#1e1e2e;color:#cdd6f4;border-radius:8px;padding:12px 14px;font-family:'D2Coding','Fira Code',monospace;font-size:13px;line-height:1.55;overflow-x:auto;margin:8px 0;white-space:pre}
.q-answer{background:#f0fdf4;border:1.5px solid #86efac;border-radius:8px;padding:10px 14px;margin-top:8px;font-weight:700;color:#166534}
.q-answer::before{content:'✅ 정답: ';color:#15803d}
.q-explanation{background:#fffbf0;border:1.5px solid #ffd43b;border-radius:8px;padding:10px 14px;margin-top:6px;font-size:14px;color:#5c4a00;line-height:1.7;white-space:pre-wrap}
.q-explanation::before{content:'💡 해설: ';font-weight:700;color:#e67700}
.btn{display:inline-flex;align-items:center;gap:5px;padding:8px 16px;border:none;border-radius:8px;font-size:14px;font-weight:600;cursor:pointer;transition:all .15s;font-family:inherit}
.btn-primary{background:var(--primary);color:#fff}
.btn-primary:hover{background:var(--primary-dk)}
.btn-outline{background:#fff;border:1.5px solid var(--primary);color:var(--primary)}
.btn-outline:hover{background:var(--primary);color:#fff}
.btn-sm{padding:5px 10px;font-size:13px}
.btn-success{background:var(--success);color:#fff}
.btn-danger{background:var(--danger);color:#fff}
select{padding:7px 12px;border:1.5px solid var(--border);border-radius:8px;font-size:14px;background:#fff;color:var(--text)}
select:focus{outline:none;border-color:var(--primary)}
.filters{display:flex;gap:10px;flex-wrap:wrap;margin-bottom:18px;align-items:center}
.stat-grid{display:grid;grid-template-columns:repeat(4,1fr);gap:12px;margin-bottom:20px}
.stat-card{background:#fff;border-radius:10px;padding:16px;text-align:center;border:1px solid var(--border)}
.stat-val{font-size:26px;font-weight:800;color:var(--primary)}
.stat-lbl{font-size:12px;color:var(--muted);margin-top:2px}
.timer{font-size:24px;font-weight:800;color:var(--primary);font-variant-numeric:tabular-nums}
.prog-bar{background:var(--border);border-radius:99px;height:6px;overflow:hidden;margin:8px 0}
.prog-bar>div{background:var(--primary);height:100%;border-radius:99px;transition:width .3s}
.score-big{font-size:64px;font-weight:900;color:var(--primary);text-align:center;line-height:1}
.hidden{display:none!important}
.text-center{text-align:center}
.mt-8{margin-top:8px}
.mt-16{margin-top:16px}
.mt-24{margin-top:24px}
.flex{display:flex}
.items-center{align-items:center}
.justify-between{justify-content:space-between}
.gap-8{gap:8px}
.hero{text-align:center;padding:56px 16px 40px}
.hero h1{font-size:34px;font-weight:900;color:var(--primary);margin-bottom:10px}
.hero p{font-size:16px;color:var(--muted);max-width:500px;margin:0 auto 28px}
.hero-grid{display:grid;grid-template-columns:1fr 1fr;gap:16px;max-width:640px;margin:0 auto}
.hero-grid-3{grid-template-columns:repeat(3,1fr);max-width:960px}
.hero-grid-4{grid-template-columns:repeat(4,1fr);max-width:1180px}
.hero-card{background:#fff;border:2px solid var(--border);border-radius:14px;padding:24px;cursor:pointer;transition:all .2s;text-decoration:none;color:var(--text);display:block}
.hero-card:hover{border-color:var(--primary);box-shadow:0 4px 16px rgba(59,91,219,.15);transform:translateY(-2px)}
.hero-card h2{font-size:20px;font-weight:800;color:var(--primary);margin-bottom:6px}
.hero-card p{font-size:14px;color:var(--muted)}
.answer-input{width:100%;padding:10px 14px;border:1.5px solid var(--border);border-radius:8px;font-size:15px;font-family:inherit}
.answer-input:focus{outline:none;border-color:var(--primary)}
.correct-mark{color:var(--success);font-weight:800}
.wrong-mark{color:var(--danger);font-weight:800}
.tag-year{background:#e7f5ff;color:#1864ab;font-size:11px;font-weight:700;padding:2px 8px;border-radius:99px}
.filter-search{flex:1;min-width:160px;padding:7px 12px;border:1.5px solid var(--border);border-radius:8px;font-size:14px;font-family:inherit}
.filter-search:focus{outline:none;border-color:var(--primary)}
@media(max-width:640px){
  header{padding:0 12px}
  header a.logo{font-size:15px}
  nav a{padding:3px 8px;font-size:12px}
  .wrap{padding:16px 10px}
  .card{padding:14px}
  .filters{gap:6px}
  .filters select{width:100%;box-sizing:border-box}
  .filter-search{width:100%;min-width:0;flex:none}
  .quiz-hint{display:none}
  .stat-grid{grid-template-columns:repeat(2,1fr)}
  .hero{padding:32px 10px 24px}
  .hero h1{font-size:22px}
  .hero-grid,.hero-grid-3,.hero-grid-4{grid-template-columns:1fr}
  .hero-card{padding:16px}
  .hero-card h2{font-size:17px}
  .timer{font-size:18px}
  .q-code{font-size:12px}
  .q-text{font-size:14px}
  select{max-width:100%}
}

@media(max-width:430px){
  body{overflow-x:hidden}
  header{padding:0 10px;gap:6px}
  header a.logo{font-size:13px;white-space:nowrap}
  nav{display:flex;gap:1px}
  nav a{padding:4px 6px;font-size:11px;white-space:nowrap}
}

.tag-book{background:#e7f5ff;color:#1864ab;font-weight:700}
.f-src-book select#f-year[disabled],select[disabled]{opacity:.5}

.q-tip{margin-top:10px;background:#f3f0ff;border:1px solid #d0bfff;border-left:4px solid #7048e8;border-radius:8px;padding:12px 14px;font-size:13.5px;line-height:1.65;color:#343a40}
.q-tip-h{font-weight:800;color:#5f3dc4;margin-bottom:6px;font-size:13px}
.q-tip p{margin:.4em 0}
.q-tip strong{color:#5f3dc4}
.q-tip code{background:#e9ecef;padding:1px 5px;border-radius:4px;font-size:12.5px}