:root {
      --bg: #121212;
      --card-bg: #1e1e1e;
      --accent: #4ea3ff;
      --accent-soft: #20476d;
      --text-main: #f5f5f5;
      --text-muted: #bbbbbb;
      --danger: #ff5c5c;
      --success: #48c774;
    }

    * {
      box-sizing: border-box;
    }

    body {
      margin: 0;
      font-family: system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
      background-color: var(--bg);
      color: var(--text-main);
      display: flex;
      justify-content: center;
      align-items: flex-start;
      min-height: 100vh;
      padding: 12px;
    }

    .app, .start-screen {
      width: 100%;
      max-width: 900px;
      margin: 0 auto;
      background-color: var(--card-bg);
      border-radius: 12px;
      padding: 16px 16px 12px;
      box-shadow: 0 10px 30px rgba(0, 0, 0, 0.5);
    }

    @media (min-width: 768px) {
      .app, .start-screen {
        padding: 20px 24px 16px;
        border-radius: 16px;
      }
    }

    .header {
      text-align: center;
      margin-bottom: 4px;
    }

    .question-number {
      font-size: 1.6rem;
      font-weight: 700;
    }

    .score-line {
      font-size: 0.85rem;
      color: var(--text-muted);
      margin-top: 2px;
    }

    .question-text {
      margin-top: 10px;
      font-size: 1.1rem;
      font-weight: 600;
      line-height: 1.5;
    }

    .answer-area {
      margin-top: 8px;
    }

    .instruction {
      font-weight: 700;
      text-decoration: underline;
      margin-bottom: 6px;
      font-size: 0.95rem;
    }

    textarea {
      width: 100%;
      min-height: 120px;
      border-radius: 8px;
      border: 1px solid #333;
      background-color: #181818;
      color: var(--text-main);
      padding: 10px;
      font-size: 1rem;
      resize: vertical;
    }

    textarea:focus {
      outline: none;
      border-color: var(--accent);
      box-shadow: 0 0 0 2px rgba(78, 163, 255, 0.3);
    }

    .options {
      display: flex;
      flex-direction: column;
      gap: 4px;
      margin-bottom: 6px;
    }

    .option {
      display: flex;
      align-items: center;
      gap: 8px;
      padding: 6px 8px;
      border-radius: 8px;
      background-color: #181818;
    }

    .option input[type="checkbox"] {
      width: 20px;
      height: 20px;
    }

    .option-label {
      flex: 1;
    }

    .btn-row {
      margin-top: 10px;
      display: flex;
      gap: 8px;
      justify-content: center;
      flex-wrap: wrap;
    }

    button {
      border: none;
      border-radius: 999px;
      padding: 10px 18px;
      font-size: 0.95rem;
      font-weight: 600;
      cursor: pointer;
      transition: background-color 0.15s ease, transform 0.05s ease;
    }

    button:active {
      transform: translateY(1px);
    }

    .btn-primary {
      background: linear-gradient(135deg, var(--accent), var(--accent-soft));
      color: #fff;
    }

    .btn-secondary {
      background-color: #333;
      color: #eee;
    }

    .btn-primary:disabled {
      opacity: 0.5;
      cursor: default;
    }
    .btn-primary:hover {
      filter: brightness(1.05);
    }

    .btn-primary:active {
      transform: translateY(1px);
      filter: brightness(0.95);
    }

    .feedback {
      margin-top: 8px;
      padding: 8px 10px;
      border-radius: 8px;
      font-size: 0.95rem;
    }

    .feedback.correct {
      background-color: rgba(72, 199, 116, 0.12);
      border: 1px solid var(--success);
      color: var(--success);
    }

    .feedback.incorrect {
      background-color: rgba(255, 92, 92, 0.12);
      border: 1px solid var(--danger);
      color: var(--danger);
    }

    .feedback pre {
      margin: 6px 0 0;
      font-family: "SF Mono", ui-monospace, Menlo, Consolas, monospace;
      color: var(--text-main);
      white-space: pre-wrap;
      word-break: break-word;
      font-size: 0.85rem;
    }

    .summary {
      margin-top: 16px;
      padding-top: 10px;
      border-top: 1px solid #333;
      font-size: 0.95rem;
    }

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

    .hidden {
      display: none !important;
    }

    .dialog-backdrop {
      position: fixed;
      inset: 0;
      background: rgba(0, 0, 0, 0.7);
      display: flex;
      align-items: center;
      justify-content: center;
      z-index: 999;
    }

    .dialog {
      background: #1c1c1c;
      border-radius: 12px;
      max-width: 900px;
      width: 95%;
      max-height: 90vh;
      display: flex;
      flex-direction: column;
      padding: 12px;
      box-shadow: 0 12px 40px rgba(0, 0, 0, 0.8);
    }

    .dialog-header {
      font-weight: 700;
      font-size: 1.1rem;
      margin-bottom: 6px;
    }

    .dialog-body {
      flex: 1;
      overflow-y: auto;
      margin-bottom: 8px;
      padding-right: 4px;
    }

    .dialog-body pre {
      font-family: "SF Mono", ui-monospace, Menlo, Consolas, monospace;
      font-size: 0.85rem;
      white-space: pre-wrap;
      word-break: break-word;
    }

    .dialog-footer {
      display: flex;
      justify-content: flex-end;
      gap: 8px;
    }

    .start-screen-title {
      font-size: 1.4rem;
      font-weight: 700;
      text-align: center;
      margin-bottom: 8px;
    }

    .start-screen-desc {
      font-size: 0.95rem;
      color: var(--text-muted);
      margin-bottom: 12px;
      text-align: center;
    }

    .set-list {
      margin-bottom: 16px;
    }

    .set-item {
      margin-bottom: 6px;
    }

    .set-item label {
      cursor: pointer;
    }

    .current-set {
      font-size: 0.85rem;
      color: var(--text-muted);
      text-align: center;
      margin-top: 4px;
    }

    .question-jump {
      display: flex;
      flex-direction: column;
      gap: 0.5rem;
      margin-top: 1rem;
    }

    .question-jump-row {
      display: flex;
      align-items: center;
      gap: 0.5rem;
    }

    .question-jump input {
      width: 5rem;
    }
    .question-image {
      max-width: 100%;
      height: auto;
      display: block;
      margin: 0 0 1rem 0;
      border-radius: 4px;
    }
    .question-nav {
      display: flex;
      flex-wrap: wrap;
      align-items: center;
      gap: 1rem;
      margin-top: 1rem;
    }

    #btnBackToSets {
      padding: 0.4rem 0.8rem;
      border-radius: 4px;
      border: none;
      cursor: pointer;
    }
    #btnBackToSets {
      background: #222;
      border: none;
      padding: 6px 14px;
      border-radius: 50px;
      font-size: 0.9rem;
      color: #eee;
      cursor: pointer;
      box-shadow: 0 0 3px rgba(0,0,0,0.4);
      transition: all 0.2s ease;
    }

    #btnBackToSets:hover {
      background: #333;
    }

    #btnBackToSets:active {
      background: #444;
    }
    .question-nav {
      display: flex;
      align-items: flex-start;  /* or center */
      gap: 1rem;
      margin-bottom: 1rem;
    }
    #btnBackToSets {
      font-size: 0.8rem;
    }
    .quiz-btn {
      background: #2a2a2a;
      border: none;
      padding: 6px 16px;
      border-radius: 20px;
      font-size: 0.9rem;
      color: #eee;
      cursor: pointer;
      transition: all 0.2s ease;
    }

    .quiz-btn:hover {
      background: #3a3a3a;
    }

    .quiz-btn:active {
      background: #4a4a4a;
    }
    /* Notes & Tips UI — matches your dark card/option style */
    .notes-screen {
      max-width: 980px;
      margin: 0 auto;
      padding: 18px 16px 28px;
      color: rgba(255, 255, 255, 0.92);
    }

    .notes-topbar {
      display: grid;
      grid-template-columns: auto 1fr auto;
      gap: 12px;
      align-items: center;
      margin-bottom: 14px;
    }

    .notes-topbar-title {
      min-width: 0;
      text-align: center;
    }

    .notes-kicker {
      font-size: 12px;
      opacity: 0.7;
      margin-bottom: 2px;
    }

    .notes-title {
      font-size: clamp(18px, 2.2vw, 26px);
      margin: 0;
      letter-spacing: 0.2px;
    }

    .notes-toolbar {
      display: grid;
      grid-template-columns: 1fr auto;
      gap: 12px;
      align-items: center;
      margin: 12px 0 18px;
    }

    .notes-search {
      display: flex;
      gap: 10px;
      align-items: center;
    }

    .notes-search-input {
      width: 100%;
      padding: 12px 14px;
      border-radius: 14px;
      border: 1px solid rgba(255, 255, 255, 0.08);
      background: rgba(0, 0, 0, 0.25);
      color: rgba(255, 255, 255, 0.92);
      outline: none;
    }

    .notes-search-input::placeholder {
      color: rgba(255, 255, 255, 0.45);
    }

    .notes-search-input:focus {
      border-color: rgba(82, 148, 255, 0.55);
      box-shadow: 0 0 0 3px rgba(82, 148, 255, 0.18);
    }

    .notes-actions {
      display: flex;
      gap: 10px;
      justify-content: flex-end;
      flex-wrap: wrap;
    }

    .notes-sections {
      display: grid;
      gap: 12px;
    }

    .notes-section {
      border-radius: 16px;
      border: 1px solid rgba(255, 255, 255, 0.08);
      background: rgba(0, 0, 0, 0.22);
      overflow: hidden;
    }

    .notes-summary {
      list-style: none;
      cursor: pointer;
      padding: 14px 16px;
      display: flex;
      align-items: center;
      justify-content: space-between;
      gap: 12px;
      user-select: none;
    }

    .notes-section > summary::-webkit-details-marker {
      display: none;
    }

    .notes-summary-title {
      font-size: 16px;
      font-weight: 700;
    }

    .notes-summary-meta {
      font-size: 12px;
      opacity: 0.65;
      white-space: nowrap;
    }

    .notes-items {
      padding: 10px 12px 14px;
      display: grid;
      gap: 10px;
    }

    .notes-item {
      display: grid;
      grid-template-columns: auto 1fr;
      gap: 12px;
      align-items: start;
      padding: 12px 12px;
      border-radius: 14px;
      background: rgba(0, 0, 0, 0.26);
      border: 1px solid rgba(255, 255, 255, 0.06);
    }

    .notes-item-text {
      line-height: 1.35;
      font-size: 14.5px;
    }

    .notes-badge {
      display: inline-flex;
      align-items: center;
      justify-content: center;
      padding: 6px 10px;
      border-radius: 999px;
      font-size: 12px;
      font-weight: 700;
      letter-spacing: 0.2px;
      border: 1px solid rgba(255, 255, 255, 0.10);
      background: rgba(255, 255, 255, 0.06);
      white-space: nowrap;
    }

    .notes-badge-rule {
      border-color: rgba(82, 148, 255, 0.35);
      background: rgba(82, 148, 255, 0.14);
    }

    .notes-badge-trap {
      border-color: rgba(255, 170, 70, 0.35);
      background: rgba(255, 170, 70, 0.14);
    }

    .notes-badge-formula {
      border-color: rgba(120, 240, 180, 0.30);
      background: rgba(120, 240, 180, 0.12);
    }

    .notes-footer {
      margin-top: 16px;
      padding-top: 12px;
      opacity: 0.8;
    }

    .notes-footer code {
      font-family: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, "Liberation Mono", "Courier New", monospace;
      font-size: 12.5px;
      padding: 2px 6px;
      border-radius: 8px;
      background: rgba(0, 0, 0, 0.28);
      border: 1px solid rgba(255, 255, 255, 0.08);
    }

    /* Buttons — re-use your existing .btn if you have it; these are safe fallbacks */
    .btn {
      padding: 10px 14px;
      border-radius: 999px;
      border: 1px solid rgba(255, 255, 255, 0.10);
      background: rgba(255, 255, 255, 0.06);
      color: rgba(255, 255, 255, 0.92);
      cursor: pointer;
    }

    .btn:hover {
      background: rgba(255, 255, 255, 0.09);
    }

    .btn:active {
      transform: translateY(1px);
    }

    .btn-secondary {
      background: rgba(0, 0, 0, 0.18);
    }

    .hidden {
      display: none !important;
    }

    /* Mobile tweaks */
    @media (max-width: 720px) {
      .notes-toolbar {
        grid-template-columns: 1fr;
      }

      .notes-topbar {
        grid-template-columns: auto 1fr auto;
      }

      .notes-title {
        font-size: 18px;
      }
    }
    .notes-summary-title {
      color: var(--accent-soft);
    }

    .question-text {
      font-size: clamp(16px, 2vw, 20px);
      font-weight: 700;
      line-height: 1.35;
      margin-bottom: 16px;
      color: var(--accent-soft);
      letter-spacing: 0.2px;
    }

    /* Optional: add a subtle left accent bar */
    .question-text::before {
      content: "";
      display: inline-block;
      width: 4px;
      height: 1.2em;
      margin-right: 10px;
      border-radius: 4px;
      background: linear-gradient(
        to bottom,
        var(--accent),
        var(--accent-soft)
      );
      vertical-align: middle;
    }
    /* Tag pills (question metadata) */
    .tag-row {
      margin-top: 10px;
      display: flex;
      flex-wrap: wrap;
      gap: 8px;
      align-items: center;
      justify-content: flex-start;
    }

    .tag-pill {
      display: inline-flex;
      align-items: center;
      gap: 6px;
      padding: 6px 10px;
      border-radius: 999px;
      font-size: 0.82rem;
      line-height: 1;
      user-select: none;
      border: 1px solid rgba(255,255,255,0.10);
      background: rgba(255,255,255,0.06);
      color: rgba(255,255,255,0.86);
    }

    .tag-pill::before {
      content: "";
      width: 7px;
      height: 7px;
      border-radius: 999px;
      background: var(--accent);
      box-shadow: 0 0 0 3px rgba(255,255,255,0.02);
      opacity: 0.9;
    }

    /* Optional: smaller on mobile */
    @media (max-width: 520px) {
      .tag-pill {
        font-size: 0.78rem;
        padding: 6px 9px;
      }
    }
    .question-text { line-height: 1.35; }

    .qtag{
      display: inline-block;
      padding: 0.15rem 0.45rem;
      border-radius: 999px;
      font-size: 0.8rem;
      font-weight: 600;
      letter-spacing: 0.03em;
      margin-right: 0.25rem;
    }

    .qtag-flag{
      color: #f0c674;                 /* amber */
      background: rgba(240,198,116,.12);
      border: 1px solid rgba(240,198,116,.25);
    }

    .qtag-set{
      color: #6fa8dc;                 /* blue */
      background: rgba(111,168,220,.12);
      border: 1px solid rgba(111,168,220,.25);
    }

    .qtext{
      color: #fff;                    /* keep question dominant */
      font-size: 1.05rem;
      font-weight: 600;
    }
    .qtext{
      color:#849db6;
      text-shadow: 0 0 0.01px rgba(255, 255, 255, 0.244);
    }
    .notes-toolbar { display:flex; align-items:center; gap:.5rem; margin: .75rem 0; }
    .notes-label { opacity: .85; font-size: .9rem; }
    #categoryFilter { padding: .35rem .5rem; border-radius: .5rem; }
    .notes-chips {
      display: flex;
      flex-wrap: wrap;
      gap: 0.5rem;
      margin: 0.75rem 0 1rem;
    }

    .notes-chip {
      padding: 0.35rem 0.75rem;
      border-radius: 999px;
      font-size: 0.8rem;
      font-weight: 600;
      cursor: pointer;
      user-select: none;
      border: 1px solid rgba(255,255,255,0.15);
      color: #cfd6dd;
      background: rgba(255,255,255,0.04);
    }

    .notes-chip:hover {
      background: rgba(255,255,255,0.08);
    }

    .notes-chip.active {
      color: #fff;
      border-color: #6fa8dc;
      background: rgba(111,168,220,0.18);
    }
/* Default (inactive) */
.notes-chip {
  border: 1px solid rgba(255,255,255,0.15);
  color: #cfd6dd;
  background: rgba(255,255,255,0.04);
}

/* Active category colours */
.notes-chip.active[data-cat="Static Field"] {
  border-color: #6fa8dc;
  background: rgba(111,168,220,0.25);
  color: #ffffff;
}

.notes-chip.active[data-cat="RF & SAR"] {
  border-color: #f4a261;
  background: rgba(244,162,97,0.25);
  color: #ffffff;
}

.notes-chip.active[data-cat="RF Heating & Burns"] {
  border-color: #e76f51;
  background: rgba(231,111,81,0.25);
  color: #ffffff;
}

.notes-chip.active[data-cat="Gradients & PNS"] {
  border-color: #9b5de5;
  background: rgba(155,93,229,0.25);
  color: #ffffff;
}

.notes-chip.active[data-cat="Implants"] {
  border-color: #2a9d8f;
  background: rgba(42,157,143,0.25);
  color: #ffffff;
}

.notes-chip.active[data-cat="Guidelines"] {
  border-color: #adb5bd;
  background: rgba(173,181,189,0.25);
  color: #ffffff;
}

.notes-chip.active[data-cat="Exam Traps"] {
  border-color: #f1c453;
  background: rgba(241,196,83,0.25);
  color: #ffffff;
}
.free-controls { display: flex; gap: 10px; margin-top: 10px; flex-wrap: wrap; }
.free-correct { padding: 10px; border-radius: 10px; background: rgba(255,255,255,0.06); }
.hidden { display: none; }