:root {
    --primary: #1a6fb5;
    --primary-dark: #135191;
    --secondary: #f0f4fa;
    --success: #2a7d4f;
    --success-bg: #e8f5ee;
    --danger: #c0392b;
    --danger-bg: #fdf0ef;
    --warn: #b7791f;
    --warn-bg: #fef9ec;
    --text: #1a1f2e;
    --muted: #6b7280;
    --border: #d1d9e6;
    --white: #ffffff;
    --radius: 10px;
    --shadow: 0 2px 12px rgba(26,111,181,0.10);
  }
  * { box-sizing: border-box; margin: 0; padding: 0; }
  body {
    font-family: 'Segoe UI', Arial, sans-serif;
    background: #eef2f8;
    color: var(--text);
    min-height: 100vh;
    display: flex;
    flex-direction: column;
    align-items: center;
    padding: 20px 16px 40px;
  }
  header {
    width: 100%;
    max-width: 800px;
    display: flex;
    align-items: center;
    gap: 14px;
    margin-bottom: 28px;
  }
  header h1 { font-size: 1.3rem; font-weight: 700; color: var(--primary); }
  header p { font-size: 0.85rem; color: var(--muted); margin-top: 2px; }

  .card {
    background: var(--white);
    border-radius: var(--radius);
    box-shadow: var(--shadow);
    padding: 28px;
    width: 100%;
    max-width: 800px;
  }

  /* ---- SCREEN: START ---- */
  #screen-start .intro { color: var(--muted); margin-bottom: 24px; line-height: 1.6; }
  .mode-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; margin-bottom: 24px; }
  @media(max-width: 520px){ .mode-grid { grid-template-columns: 1fr; } }
  .mode-card {
    border: 2px solid var(--border);
    border-radius: var(--radius);
    padding: 18px;
    cursor: pointer;
    transition: all .18s;
    text-align: left;
  }
  .mode-card:hover { border-color: var(--primary); background: var(--secondary); }
  .mode-card.active { border-color: var(--primary); background: #e5eef8; }
  .mode-card h3 { font-size: 1rem; margin-bottom: 6px; }
  .mode-card p { font-size: 0.82rem; color: var(--muted); line-height: 1.5; }

  .category-select { margin-bottom: 20px; display: none; }
  .category-select label { font-weight: 600; display: block; margin-bottom: 8px; }
  .category-select select {
    width: 100%; padding: 10px 12px; border-radius: 8px;
    border: 1.5px solid var(--border); font-size: 0.95rem;
    background: var(--secondary); cursor: pointer;
  }

  .btn {
    display: inline-flex; align-items: center; justify-content: center; gap: 8px;
    padding: 12px 28px; border-radius: 8px; font-size: 1rem; font-weight: 600;
    cursor: pointer; border: none; transition: background .15s, transform .1s;
  }
  .btn:active { transform: scale(0.98); }
  .btn-primary { background: var(--primary); color: white; }
  .btn-primary:hover { background: var(--primary-dark); }
  .btn-secondary { background: var(--secondary); color: var(--primary); border: 2px solid var(--border); }
  .btn-secondary:hover { background: #dce5f0; }
  .btn-full { width: 100%; }

  /* ---- SCREEN: QUIZ ---- */
  #screen-quiz { display: none; }
  .quiz-header { margin-bottom: 20px; }
  .quiz-meta { display: flex; justify-content: space-between; align-items: center; margin-bottom: 12px; flex-wrap: wrap; gap: 8px; }
  .quiz-category { font-size: 0.8rem; font-weight: 600; color: var(--primary); background: var(--secondary); padding: 4px 10px; border-radius: 20px; }
  .quiz-counter { font-size: 0.85rem; color: var(--muted); }
  .progress-bar { width: 100%; height: 6px; background: var(--border); border-radius: 3px; overflow: hidden; }
  .progress-fill { height: 100%; background: var(--primary); border-radius: 3px; transition: width .3s; }

  .question-text { font-size: 1.05rem; font-weight: 600; line-height: 1.55; margin-bottom: 20px; }

  .options { display: flex; flex-direction: column; gap: 10px; }
  .option {
    padding: 13px 16px;
    border: 2px solid var(--border);
    border-radius: 8px;
    cursor: pointer;
    font-size: 0.95rem;
    line-height: 1.45;
    transition: all .15s;
    display: flex; align-items: flex-start; gap: 10px;
  }
  .option:hover:not(.disabled) { border-color: var(--primary); background: var(--secondary); }
  .option-letter {
    width: 24px; height: 24px; min-width: 24px;
    border-radius: 50%; background: var(--secondary); border: 2px solid var(--border);
    display: flex; align-items: center; justify-content: center;
    font-size: 0.8rem; font-weight: 700; color: var(--muted);
  }
  .option.selected .option-letter { background: var(--primary); border-color: var(--primary); color: white; }
  .option.selected { border-color: var(--primary); background: #e5eef8; }
  .option.correct { border-color: var(--success); background: var(--success-bg); }
  .option.correct .option-letter { background: var(--success); border-color: var(--success); color: white; }
  .option.wrong { border-color: var(--danger); background: var(--danger-bg); }
  .option.wrong .option-letter { background: var(--danger); border-color: var(--danger); color: white; }
  .option.disabled { cursor: default; }

  .explanation {
    margin-top: 16px; padding: 14px 16px;
    border-radius: 8px; font-size: 0.88rem; line-height: 1.5; display: none;
  }
  .explanation.correct-exp { background: var(--success-bg); border-left: 3px solid var(--success); color: #1a5e38; }
  .explanation.wrong-exp { background: var(--danger-bg); border-left: 3px solid var(--danger); color: #8b1a10; }

  .quiz-nav { display: flex; justify-content: space-between; align-items: center; margin-top: 22px; gap: 12px; }

  /* ---- SCREEN: RESULTS ---- */
  #screen-results { display: none; }
  .result-summary { text-align: center; padding: 28px 20px; }
  .result-score-circle {
    width: 110px; height: 110px; border-radius: 50%;
    display: flex; flex-direction: column; align-items: center; justify-content: center;
    margin: 0 auto 16px; font-weight: 700;
    border: 6px solid var(--border);
  }
  .result-score-circle.pass { border-color: var(--success); color: var(--success); }
  .result-score-circle.fail { border-color: var(--danger); color: var(--danger); }
  .result-score-circle .score-num { font-size: 2rem; line-height: 1; }
  .result-score-circle .score-pct { font-size: 0.85rem; }
  .result-verdict { font-size: 1.3rem; font-weight: 700; margin-bottom: 8px; }
  .result-verdict.pass { color: var(--success); }
  .result-verdict.fail { color: var(--danger); }
  .result-info { font-size: 0.88rem; color: var(--muted); margin-bottom: 24px; line-height: 1.5; }

  .category-breakdown { margin-top: 8px; }
  .category-breakdown h3 { font-size: 0.95rem; font-weight: 700; margin-bottom: 14px; color: var(--text); }
  .cat-row { display: flex; align-items: center; gap: 10px; margin-bottom: 10px; flex-wrap: wrap; }
  .cat-name { font-size: 0.82rem; width: 210px; min-width: 160px; color: var(--text); }
  .cat-bar-wrap { flex: 1; height: 10px; background: var(--border); border-radius: 5px; min-width: 80px; position: relative; }
  .cat-bar { height: 100%; border-radius: 5px; }
  .cat-bar.good { background: var(--success); }
  .cat-bar.mid { background: var(--warn); }
  .cat-bar.bad { background: var(--danger); }
  .cat-bar-threshold { position: absolute; top: -3px; bottom: -3px; width: 2px; background: var(--muted); border-radius: 1px; opacity: 0.5; }
  .cat-score { font-size: 0.78rem; color: var(--muted); white-space: nowrap; }
  .cat-status { font-size: 0.72rem; font-weight: 700; padding: 2px 7px; border-radius: 10px; white-space: nowrap; }
  .cat-status.ce-pass { background: var(--success-bg); color: var(--success); }
  .cat-status.ce-fail { background: #fde8e8; color: var(--danger); }
  .cat-row.not-tested .cat-name { color: var(--muted); }

  .result-actions { display: flex; gap: 12px; margin-top: 24px; flex-wrap: wrap; }
  .result-actions .btn { flex: 1; min-width: 140px; }

  /* ---- Misc ---- */
  .badge {
    display: inline-block; font-size: 0.7rem; font-weight: 700;
    padding: 2px 8px; border-radius: 20px;
    background: var(--secondary); color: var(--primary);
    border: 1px solid var(--border);
    vertical-align: middle; margin-left: 6px;
  }
  .hidden { display: none !important; }

  /* ---- TYPE & DIFFICULTY FILTER ---- */
  .type-filter-wrap { margin-bottom: 12px; }
  .diff-filter-wrap { margin-bottom: 16px; }
  .type-filter-wrap label.group-label { font-weight: 600; font-size: 0.88rem; display: block; margin-bottom: 8px; }
  .type-checks { display: flex; gap: 10px; flex-wrap: wrap; }
  .type-check {
    display: flex; align-items: center; gap: 7px; padding: 7px 14px;
    border: 1.5px solid var(--border); border-radius: 8px; cursor: pointer;
    font-size: 0.88rem; transition: all .15s; user-select: none;
  }
  .type-check:has(input:checked) { border-color: var(--primary); background: #e5eef8; color: var(--primary); font-weight: 600; }
  .type-check input { width: 15px; height: 15px; accent-color: var(--primary); cursor: pointer; }

  /* ---- DIFFICULTY BADGES ---- */
  .diff-badge { font-size: 0.68rem; font-weight: 700; padding: 2px 7px; border-radius: 10px;
    display: inline-block; margin-left: 4px; vertical-align: middle; }
  .diff-badge.easy   { background: #dcfce7; color: #166534; }
  .diff-badge.medium { background: #e0f2fe; color: #075985; }
  .diff-badge.hard   { background: #fee2e2; color: #991b1b; }
  .q-diff-hint { font-size: 0.75rem; font-weight: 600; padding: 3px 9px; border-radius: 12px;
    margin-left: 4px; display: none; border: 1px solid transparent; }
  .q-diff-hint.visible { display: inline; }
  .q-diff-hint.easy   { background: #dcfce7; color: #166534; border-color: #bbf7d0; }
  .q-diff-hint.medium { background: #e0f2fe; color: #075985; border-color: #bae6fd; }
  .q-diff-hint.hard   { background: #fee2e2; color: #991b1b; border-color: #fecaca; }

  /* ---- QUIZ: MULTI & OPEN ---- */
  .q-type-hint { font-size: 0.75rem; font-weight: 600; padding: 3px 9px; border-radius: 12px;
    background: #fff3cd; color: #856404; border: 1px solid #ffc107; margin-left: 6px; display: none; }
  .q-type-hint.visible { display: inline; }
  .option-checkbox { width: 17px; height: 17px; accent-color: var(--primary); cursor: pointer; flex-shrink: 0; margin-top: 2px; }
  .open-answer-wrap { display: flex; flex-direction: column; gap: 10px; }
  .open-answer-input {
    width: 100%; padding: 12px 16px; border-radius: 8px; border: 2px solid var(--border);
    font-size: 1rem; font-family: inherit; background: var(--secondary); transition: border-color .15s;
  }
  .open-answer-input:focus { outline: none; border-color: var(--primary); background: var(--white); }
  .open-answer-input.correct { border-color: var(--success); background: var(--success-bg); }
  .open-answer-input.wrong  { border-color: var(--danger);  background: var(--danger-bg); }
  .open-answer-hint { font-size: 0.85rem; color: var(--muted); padding: 8px 12px; background: var(--danger-bg);
    border-radius: 6px; border-left: 3px solid var(--danger); }
  .quiz-nav-right { display: flex; gap: 10px; }

  /* ---- EDITOR: TYPE BADGE ---- */
  .type-badge { font-size: 0.68rem; font-weight: 700; padding: 2px 7px; border-radius: 10px;
    display: inline-block; margin-left: 6px; vertical-align: middle; }
  .type-badge.single { background: #e0f2fe; color: #075985; }
  .type-badge.multi  { background: #fef9c3; color: #854d0e; }
  .type-badge.open   { background: #f0fdf4; color: #166534; }

  /* ---- SCREEN: EDITOR ---- */
  .editor-topbar { display: flex; justify-content: space-between; align-items: center; flex-wrap: wrap; gap: 12px; margin-bottom: 18px; }
  .editor-topbar h2 { font-size: 1.1rem; font-weight: 700; }
  .editor-toolbar { display: flex; gap: 10px; flex-wrap: wrap; align-items: center; }
  .editor-toolbar select {
    padding: 8px 12px; border-radius: 8px; border: 1.5px solid var(--border);
    font-size: 0.88rem; background: var(--secondary); cursor: pointer; min-width: 200px;
  }
  .btn-sm { padding: 7px 16px; font-size: 0.85rem; }
  .btn-danger { background: var(--danger-bg); color: var(--danger); border: 2px solid #f5c6c2; }
  .btn-danger:hover { background: #f9dfdc; }
  .editor-stats { font-size: 0.82rem; color: var(--muted); margin-bottom: 14px; }

  .q-list { display: flex; flex-direction: column; gap: 8px; margin-bottom: 24px; }
  .q-item {
    border: 1.5px solid var(--border); border-radius: 8px; padding: 12px 14px;
    display: flex; align-items: flex-start; gap: 12px; background: var(--white);
  }
  .q-item.is-custom { border-color: #93c5fd; background: #f0f7ff; }
  .q-item-body { flex: 1; min-width: 0; }
  .q-item-cat { font-size: 0.72rem; font-weight: 700; color: var(--primary); margin-bottom: 4px; }
  .q-item-text { font-size: 0.9rem; line-height: 1.4; color: var(--text); }
  .q-item-text.truncate { white-space: nowrap; overflow: hidden; text-overflow: ellipsis; }
  .q-item-actions { display: flex; gap: 6px; flex-shrink: 0; }
  .btn-icon {
    width: 32px; height: 32px; border-radius: 6px; border: 1.5px solid var(--border);
    background: var(--secondary); cursor: pointer; display: flex; align-items: center;
    justify-content: center; font-size: 0.9rem; transition: all .15s;
  }
  .btn-icon:hover { border-color: var(--primary); background: #e5eef8; }
  .btn-icon.del:hover { border-color: var(--danger); background: var(--danger-bg); }

  .editor-footer { display: flex; justify-content: space-between; gap: 12px; flex-wrap: wrap; border-top: 1px solid var(--border); padding-top: 20px; }

  .empty-state { text-align: center; padding: 32px; color: var(--muted); font-size: 0.9rem; }

  /* ---- MODAL ---- */
  .modal-overlay {
    display: none; position: fixed; inset: 0;
    background: rgba(0,0,0,0.45); z-index: 1000;
    align-items: center; justify-content: center; padding: 16px;
  }
  .modal-overlay.open { display: flex; }
  .modal-card {
    background: var(--white); border-radius: var(--radius);
    box-shadow: 0 8px 40px rgba(0,0,0,0.22); width: 100%; max-width: 580px;
    max-height: 90vh; display: flex; flex-direction: column;
  }
  .modal-header {
    padding: 20px 24px 16px; border-bottom: 1px solid var(--border);
    display: flex; align-items: center; justify-content: space-between; flex-shrink: 0;
  }
  .modal-header h3 { font-size: 1.05rem; font-weight: 700; }
  .modal-close {
    width: 30px; height: 30px; border-radius: 6px; border: none;
    background: var(--secondary); cursor: pointer; font-size: 1rem;
    display: flex; align-items: center; justify-content: center;
  }
  .modal-close:hover { background: var(--border); }
  .modal-body { padding: 20px 24px; overflow-y: auto; flex: 1; }
  .modal-footer { padding: 16px 24px; border-top: 1px solid var(--border); display: flex; gap: 10px; justify-content: flex-end; flex-shrink: 0; }

  .form-group { margin-bottom: 16px; }
  .form-group label { display: block; font-size: 0.85rem; font-weight: 600; margin-bottom: 6px; color: var(--text); }
  .form-group select,
  .form-group textarea,
  .form-group input[type="text"] {
    width: 100%; padding: 9px 12px; border-radius: 7px;
    border: 1.5px solid var(--border); font-size: 0.9rem; font-family: inherit;
    background: var(--secondary); color: var(--text); resize: vertical;
  }
  .form-group select:focus,
  .form-group textarea:focus,
  .form-group input[type="text"]:focus {
    outline: none; border-color: var(--primary); background: var(--white);
  }
  .options-edit { display: flex; flex-direction: column; gap: 8px; }
  .option-edit-row {
    display: flex; align-items: center; gap: 8px;
    padding: 8px 10px; border-radius: 7px; border: 1.5px solid var(--border); background: var(--white);
    transition: border-color .15s;
  }
  .option-edit-row:has(input[type="radio"]:checked) { border-color: var(--success); background: var(--success-bg); }
  .option-edit-row input[type="radio"] { width: 16px; height: 16px; accent-color: var(--success); flex-shrink: 0; cursor: pointer; }
  .option-edit-row:has(.edit-correct-multi:checked) { border-color: var(--success); background: var(--success-bg); }
  .option-edit-row .opt-letter { font-size: 0.78rem; font-weight: 700; color: var(--muted); width: 16px; flex-shrink: 0; }
  .option-edit-row input[type="text"] { border: none; background: transparent; padding: 0; flex: 1; }
  .option-edit-row input[type="text"]:focus { outline: none; }
  .form-hint { font-size: 0.75rem; color: var(--muted); margin-top: 5px; }