@import url('https://fonts.googleapis.com/css2?family=Bebas+Neue&family=DM+Sans:ital,wght@0,300;0,400;0,500;0,600;1,400&family=DM+Mono:wght@400;500&display=swap');

  :root {
    --bg: #0a0a0f;
    --surface: #13131a;
    --surface2: #1c1c28;
    --border: #2a2a3d;
    --accent: #f5a623;
    --accent2: #e74c3c;
    --accent3: #2ecc71;
    --accent4: #3498db;
    --text: #e8e8f0;
    --muted: #6b6b85;
    --correct: #27ae60;
    --wrong: #c0392b;
  }

  * { margin: 0; padding: 0; box-sizing: border-box; }

  body {
    background: var(--bg);
    color: var(--text);
    font-family: 'DM Sans', sans-serif;
    min-height: 100vh;
    overflow-x: hidden;
  }

  header {
    background: var(--surface);
    border-bottom: 1px solid var(--border);
    padding: 0 2rem;
    display: flex;
    align-items: center;
    justify-content: space-between;
    height: 64px;
    position: sticky;
    top: 0;
    z-index: 100;
  }

  .logo { font-family: 'Bebas Neue', sans-serif; font-size: 1.6rem; letter-spacing: 2px; color: var(--accent); }
  .logo span { color: var(--text); }

  .version-badge {
    background: var(--accent3);
    color: #000;
    padding: 4px 12px;
    border-radius: 4px;
    font-family: 'DM Mono', monospace;
    font-size: 0.75rem;
    font-weight: 500;
  }

  .app { display: flex; height: calc(100vh - 64px); }

  .sidebar {
    width: 270px;
    min-width: 270px;
    background: var(--surface);
    border-right: 1px solid var(--border);
    overflow-y: auto;
    padding: 1rem 0;
  }

  .sidebar-section {
    padding: 0.5rem 1rem 0.25rem;
    font-family: 'DM Mono', monospace;
    font-size: 0.62rem;
    letter-spacing: 2px;
    color: var(--muted);
    text-transform: uppercase;
    margin-top: 0.75rem;
  }

  .nav-item {
    display: flex;
    align-items: center;
    gap: 10px;
    padding: 9px 1.25rem;
    cursor: pointer;
    border-left: 3px solid transparent;
    font-size: 0.825rem;
    font-weight: 500;
    color: var(--muted);
    transition: all 0.15s;
  }

  .nav-item:hover { color: var(--text); background: var(--surface2); }
  .nav-item.active { color: var(--accent); border-left-color: var(--accent); background: var(--surface2); }

  .nav-badge {
    margin-left: auto;
    background: var(--border);
    color: var(--muted);
    font-size: 0.65rem;
    padding: 2px 6px;
    border-radius: 10px;
    font-family: 'DM Mono', monospace;
  }

  .nav-item.active .nav-badge { background: var(--accent); color: #000; }
  .nav-badge.new { background: var(--accent3); color: #000; }

  .main { flex: 1; overflow-y: auto; padding: 2rem; }

  .view { display: none; }
  .view.active { display: block; }

  /* DASHBOARD */
  .dash-grid {
    display: grid;
    grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
    gap: 1rem;
    margin-bottom: 2rem;
  }

  .stat-card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 1.25rem;
  }

  .stat-label { font-size: 0.68rem; letter-spacing: 1.5px; text-transform: uppercase; color: var(--muted); font-family: 'DM Mono', monospace; margin-bottom: 0.5rem; }
  .stat-value { font-family: 'Bebas Neue', sans-serif; font-size: 2.5rem; color: var(--accent); line-height: 1; }
  .stat-sub { font-size: 0.72rem; color: var(--muted); margin-top: 4px; }

  .section-title { font-family: 'Bebas Neue', sans-serif; font-size: 1.5rem; letter-spacing: 1px; margin-bottom: 1rem; color: var(--text); }

  .topic-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(260px, 1fr)); gap: 1rem; margin-bottom: 2rem; }

  .topic-card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 1.25rem;
    cursor: pointer;
    transition: all 0.2s;
    position: relative;
    overflow: hidden;
  }

  .topic-card::before {
    content: '';
    position: absolute;
    top: 0; left: 0;
    width: 3px; height: 100%;
    background: var(--accent);
    opacity: 0;
    transition: opacity 0.2s;
  }

  .topic-card:hover { border-color: var(--accent); transform: translateY(-2px); }
  .topic-card:hover::before { opacity: 1; }

  .topic-name { font-weight: 600; font-size: 0.9rem; margin-bottom: 0.4rem; }
  .topic-desc { font-size: 0.78rem; color: var(--muted); line-height: 1.5; }

  .topic-meta { display: flex; gap: 0.5rem; margin-top: 0.75rem; flex-wrap: wrap; }

  .tag {
    background: var(--surface2);
    border: 1px solid var(--border);
    border-radius: 4px;
    padding: 2px 7px;
    font-size: 0.65rem;
    color: var(--muted);
    font-family: 'DM Mono', monospace;
  }

  .tag.hot { border-color: var(--accent2); color: var(--accent2); }
  .tag.ny { border-color: var(--accent); color: var(--accent); }
  .tag.new { border-color: var(--accent3); color: var(--accent3); }
  .tag.blue { border-color: var(--accent4); color: var(--accent4); }

  /* STUDY VIEWS */
  .study-header {
    display: flex;
    align-items: center;
    gap: 1rem;
    margin-bottom: 2rem;
  }

  .back-btn {
    background: var(--surface);
    border: 1px solid var(--border);
    color: var(--text);
    padding: 8px 16px;
    border-radius: 6px;
    cursor: pointer;
    font-family: 'DM Sans', sans-serif;
    font-size: 0.875rem;
    transition: all 0.15s;
  }

  .back-btn:hover { border-color: var(--accent); color: var(--accent); }

  .content-block {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 1.5rem;
    margin-bottom: 1rem;
  }

  .content-block h3 {
    font-family: 'Bebas Neue', sans-serif;
    font-size: 1.15rem;
    letter-spacing: 1px;
    color: var(--accent);
    margin-bottom: 1rem;
  }

  .content-block p { font-size: 0.88rem; line-height: 1.7; color: var(--text); margin-bottom: 0.75rem; }

  .key-point {
    background: var(--surface2);
    border-left: 3px solid var(--accent);
    padding: 0.75rem 1rem;
    border-radius: 0 6px 6px 0;
    margin: 0.5rem 0;
    font-size: 0.85rem;
    line-height: 1.6;
  }

  .key-point strong { color: var(--accent); }

  .rule-box {
    background: rgba(245,166,35,0.07);
    border: 1px solid rgba(245,166,35,0.3);
    border-radius: 6px;
    padding: 1rem;
    margin: 0.75rem 0;
    font-size: 0.85rem;
    line-height: 1.7;
  }

  .rule-box .rule-title { font-family: 'DM Mono', monospace; font-size: 0.65rem; letter-spacing: 1.5px; color: var(--accent); margin-bottom: 0.5rem; text-transform: uppercase; }

  .warning-box {
    background: rgba(231,76,60,0.07);
    border: 1px solid rgba(231,76,60,0.3);
    border-radius: 6px;
    padding: 1rem;
    margin: 0.75rem 0;
    font-size: 0.85rem;
    line-height: 1.7;
  }

  .warning-box .rule-title { font-family: 'DM Mono', monospace; font-size: 0.65rem; letter-spacing: 1.5px; color: var(--accent2); margin-bottom: 0.5rem; text-transform: uppercase; }

  .tip-box {
    background: rgba(46,204,113,0.07);
    border: 1px solid rgba(46,204,113,0.3);
    border-radius: 6px;
    padding: 1rem;
    margin: 0.75rem 0;
    font-size: 0.85rem;
    line-height: 1.7;
  }

  .tip-box .rule-title { font-family: 'DM Mono', monospace; font-size: 0.65rem; letter-spacing: 1.5px; color: var(--accent3); margin-bottom: 0.5rem; text-transform: uppercase; }

  .info-box {
    background: rgba(52,152,219,0.07);
    border: 1px solid rgba(52,152,219,0.3);
    border-radius: 6px;
    padding: 1rem;
    margin: 0.75rem 0;
    font-size: 0.85rem;
    line-height: 1.7;
  }

  .info-box .rule-title { font-family: 'DM Mono', monospace; font-size: 0.65rem; letter-spacing: 1.5px; color: var(--accent4); margin-bottom: 0.5rem; text-transform: uppercase; }

  table { width: 100%; border-collapse: collapse; margin: 0.75rem 0; font-size: 0.82rem; }
  th { background: var(--surface2); color: var(--accent); font-family: 'DM Mono', monospace; font-size: 0.68rem; letter-spacing: 1px; text-transform: uppercase; padding: 8px 12px; text-align: left; border: 1px solid var(--border); }
  td { padding: 8px 12px; border: 1px solid var(--border); line-height: 1.5; vertical-align: top; }
  tr:nth-child(even) td { background: rgba(255,255,255,0.02); }

  /* FLASHCARDS */
  .flashcard-area { max-width: 680px; margin: 0 auto; }
  .card-counter { text-align: center; font-family: 'DM Mono', monospace; font-size: 0.75rem; color: var(--muted); margin-bottom: 0.5rem; }

  .flashcard {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 12px;
    padding: 2.5rem;
    min-height: 200px;
    display: flex;
    flex-direction: column;
    justify-content: center;
    cursor: pointer;
    transition: all 0.2s;
    margin: 1rem 0;
  }

  .flashcard:hover { border-color: var(--accent); }

  .card-label { font-family: 'DM Mono', monospace; font-size: 0.65rem; letter-spacing: 1.5px; color: var(--muted); text-transform: uppercase; margin-bottom: 1rem; }
  .card-question { font-size: 1.2rem; font-weight: 600; line-height: 1.5; }
  .card-answer { font-size: 1rem; line-height: 1.7; color: var(--accent); font-weight: 500; }
  .card-hint { font-size: 0.8rem; color: var(--muted); margin-top: 1rem; line-height: 1.5; }
  .card-topic { font-family: 'DM Mono', monospace; font-size: 0.6rem; color: var(--accent4); text-transform: uppercase; letter-spacing: 1px; margin-bottom: 0.5rem; }
  .flip-hint { text-align: center; font-size: 0.78rem; color: var(--muted); margin-bottom: 1rem; }

  .card-actions { display: flex; gap: 0.75rem; justify-content: center; margin-top: 0.5rem; }

  /* QUIZ */
  .quiz-area { max-width: 720px; margin: 0 auto; }
  .quiz-meta { display: flex; gap: 1rem; margin-bottom: 1rem; align-items: center; flex-wrap: wrap; }
  .quiz-topic-badge { background: var(--surface2); border: 1px solid var(--border); border-radius: 4px; padding: 3px 10px; font-family: 'DM Mono', monospace; font-size: 0.65rem; color: var(--accent4); }
  .quiz-question { font-size: 1.05rem; font-weight: 600; line-height: 1.6; margin-bottom: 1.5rem; background: var(--surface); border: 1px solid var(--border); border-radius: 8px; padding: 1.5rem; }
  .quiz-options { display: flex; flex-direction: column; gap: 0.75rem; margin-bottom: 1rem; }
  .quiz-option { background: var(--surface); border: 1px solid var(--border); color: var(--text); padding: 1rem 1.25rem; border-radius: 8px; cursor: pointer; text-align: left; font-family: 'DM Sans', sans-serif; font-size: 0.9rem; line-height: 1.5; transition: all 0.15s; }
  .quiz-option:hover:not(:disabled) { border-color: var(--accent); color: var(--accent); }
  .quiz-option.correct { border-color: var(--correct); background: rgba(39,174,96,0.12); color: var(--accent3); }
  .quiz-option.wrong { border-color: var(--wrong); background: rgba(192,57,43,0.12); color: var(--accent2); }
  .quiz-explanation { background: var(--surface2); border: 1px solid var(--border); border-radius: 8px; padding: 1.25rem; font-size: 0.875rem; line-height: 1.7; display: none; margin-bottom: 1rem; }
  .quiz-explanation.show { display: block; }
  .quiz-nav { display: flex; align-items: center; justify-content: space-between; margin-top: 1rem; }
  .quiz-score { font-family: 'DM Mono', monospace; font-size: 0.8rem; color: var(--muted); }
  .score-display { text-align: center; padding: 3rem; background: var(--surface); border: 1px solid var(--border); border-radius: 12px; }
  .score-big { font-family: 'Bebas Neue', sans-serif; font-size: 6rem; color: var(--accent); line-height: 1; }
  .score-label { font-size: 1rem; color: var(--muted); margin-top: 0.5rem; }

  /* DRILL MODE */
  .drill-grid { display: grid; grid-template-columns: repeat(auto-fill, minmax(240px, 1fr)); gap: 1rem; margin-bottom: 2rem; }
  .drill-card {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 1.25rem;
    cursor: pointer;
    transition: all 0.2s;
  }
  .drill-card:hover { border-color: var(--accent4); transform: translateY(-2px); }
  .drill-card h4 { font-size: 0.9rem; font-weight: 600; margin-bottom: 0.4rem; }
  .drill-card p { font-size: 0.75rem; color: var(--muted); }
  .drill-count { font-family: 'DM Mono', monospace; font-size: 0.65rem; color: var(--accent4); margin-top: 0.5rem; }

  /* MATH */
  .math-problem { background: var(--surface); border: 1px solid var(--border); border-radius: 8px; padding: 1.5rem; margin-bottom: 1rem; }
  .math-problem h4 { font-weight: 600; margin-bottom: 0.75rem; font-size: 0.95rem; }
  .math-problem p { font-size: 0.875rem; color: var(--muted); margin-bottom: 1rem; line-height: 1.6; }
  .math-input { display: flex; gap: 0.75rem; align-items: center; flex-wrap: wrap; }
  .math-input input { background: var(--surface2); border: 1px solid var(--border); color: var(--text); padding: 8px 14px; border-radius: 6px; font-family: 'DM Mono', monospace; font-size: 0.875rem; width: 160px; }
  .math-input input:focus { outline: none; border-color: var(--accent); }
  .math-result { font-family: 'DM Mono', monospace; font-size: 0.85rem; margin-top: 0.5rem; }
  .math-result.correct { color: var(--accent3); }
  .math-result.wrong { color: var(--accent2); }
  .math-exp { font-size: 0.82rem; color: var(--muted); margin-top: 0.5rem; line-height: 1.6; display: none; }

  /* BUTTONS */
  .btn { padding: 10px 20px; border-radius: 6px; cursor: pointer; font-family: 'DM Sans', sans-serif; font-size: 0.875rem; font-weight: 500; border: none; transition: all 0.15s; }
  .btn-primary { background: var(--accent); color: #000; }
  .btn-primary:hover { background: #e09020; }
  .btn-outline { background: transparent; border: 1px solid var(--border); color: var(--text); }
  .btn-outline:hover { border-color: var(--accent); color: var(--accent); }
  .btn-got-it { background: rgba(39,174,96,0.15); border: 1px solid var(--correct); color: var(--accent3); }
  .btn-missed { background: rgba(192,57,43,0.15); border: 1px solid var(--wrong); color: var(--accent2); }
  .btn-blue { background: var(--accent4); color: #fff; }
  .btn-blue:hover { background: #2980b9; }

  .hidden { display: none !important; }

  .progress-bar-wrap { background: var(--border); border-radius: 4px; height: 4px; margin-bottom: 1rem; }
  .progress-bar-fill { background: var(--accent); height: 100%; border-radius: 4px; transition: width 0.3s; }

  .two-col { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem; }
  @media (max-width: 640px) { .two-col { grid-template-columns: 1fr; } }

  /* FORMULA CARD */
  .formula-card {
    background: linear-gradient(135deg, rgba(245,166,35,0.08) 0%, rgba(52,152,219,0.05) 100%);
    border: 1px solid rgba(245,166,35,0.3);
    border-radius: 8px;
    padding: 1.25rem;
    margin: 0.75rem 0;
    font-family: 'DM Mono', monospace;
    font-size: 0.9rem;
    text-align: center;
  }

  .formula-card .formula { font-size: 1.1rem; color: var(--accent); font-weight: 500; margin: 0.5rem 0; }
  .formula-card .formula-label { font-size: 0.65rem; color: var(--muted); letter-spacing: 1.5px; text-transform: uppercase; }

  .code-inline {
    font-family: 'DM Mono', monospace;
    font-size: 0.78rem;
    background: var(--surface2);
    padding: 2px 6px;
    border-radius: 4px;
    border: 1px solid var(--border);
  }

  .link-accent { color: var(--accent4); }
  .link-accent:hover { color: var(--accent); }

  .syllabus-root { max-width: 900px; }
  .syllabus-section {
    background: var(--surface);
    border: 1px solid var(--border);
    border-radius: 8px;
    padding: 1.25rem 1.5rem;
    margin-bottom: 1rem;
  }
  .syllabus-section-head {
    display: flex;
    flex-wrap: wrap;
    align-items: baseline;
    justify-content: space-between;
    gap: 0.5rem;
    margin-bottom: 1rem;
    padding-bottom: 0.75rem;
    border-bottom: 1px solid var(--border);
  }
  .syllabus-section-title {
    font-family: 'Bebas Neue', sans-serif;
    font-size: 1.25rem;
    letter-spacing: 1px;
    color: var(--accent);
  }
  .syllabus-hours {
    font-family: 'DM Mono', monospace;
    font-size: 0.7rem;
    color: var(--muted);
    letter-spacing: 1px;
  }
  .syllabus-item {
    margin-bottom: 1rem;
    font-size: 0.86rem;
    line-height: 1.55;
    color: var(--text);
  }
  .syllabus-item:last-child { margin-bottom: 0; }
  .syllabus-bullets { color: var(--muted); font-size: 0.82rem; margin: 0.35rem 0 0.5rem; }
  .syllabus-links { display: flex; flex-wrap: wrap; gap: 0.5rem; margin-top: 0.35rem; }
  .syllabus-link {
    font-family: 'DM Mono', monospace;
    font-size: 0.68rem;
    padding: 4px 10px;
    border-radius: 4px;
    border: 1px solid var(--border);
    background: var(--surface2);
    color: var(--accent4);
    cursor: pointer;
    transition: all 0.15s;
  }
  .syllabus-link:hover {
    border-color: var(--accent);
    color: var(--accent);
  }