* { box-sizing: border-box; margin: 0; padding: 0; }
  body {
    font-family: 'Plus Jakarta Sans', -apple-system, BlinkMacSystemFont, sans-serif;
    background-color: var(--bg-canvas);
    color: var(--text-primary);
    line-height: 1.5;
    padding: 32px 20px 80px 20px;
    transition: background-color 0.2s ease, color 0.2s ease;
    -webkit-font-smoothing: antialiased;
  }

  .container {
    max-width: 1240px;
    margin: 0 auto;
  }

  /* Header Bar */
  .spec-header {
    display: flex;
    flex-direction: column;
    gap: 12px;
    margin-bottom: 32px;
    padding-bottom: 24px;
    border-bottom: 1px solid var(--border-subtle);
  }
  @media (min-width: 768px) {
    .spec-header {
      flex-direction: row;
      justify-content: space-between;
      align-items: flex-start;
    }
  }
  .tagline {
    font-family: 'JetBrains Mono', monospace;
    font-size: 11px;
    font-weight: 600;
    letter-spacing: 0.08em;
    text-transform: uppercase;
    color: var(--text-muted);
  }
  .spec-title {
    font-size: 26px;
    font-weight: 700;
    color: var(--text-primary);
    letter-spacing: -0.02em;
    margin-top: 4px;
  }
  .spec-desc {
    font-size: 14px;
    color: var(--text-secondary);
    max-width: 720px;
    margin-top: 6px;
  }
  .theme-toggle-btn {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    height: 40px;
    padding: 0 16px;
    border-radius: 8px;
    border: 1px solid var(--border-strong);
    background: var(--bg-surface);
    color: var(--text-primary);
    font-size: 13px;
    font-weight: 600;
    cursor: pointer;
    box-shadow: var(--shadow-sm);
    transition: all 0.15s ease;
  }
  .theme-toggle-btn:focus-visible {
    outline: 2px solid var(--focus-ring);
    outline-offset: 2px;
  }

  /* Section Styles */
  .spec-section {
    background: var(--bg-surface);
    border: 1px solid var(--border-subtle);
    border-radius: 12px;
    padding: 24px;
    margin-bottom: 32px;
    box-shadow: var(--shadow-sm);
  }
  .section-title {
    font-size: 18px;
    font-weight: 700;
    color: var(--text-primary);
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    margin-bottom: 8px;
  }
  .section-badge {
    font-family: 'JetBrains Mono', monospace;
    font-size: 11px;
    background: var(--bg-surface-subtle);
    padding: 3px 8px;
    border-radius: 4px;
    color: var(--text-secondary);
    font-weight: 500;
  }
  .section-desc {
    font-size: 13px;
    color: var(--text-secondary);
    margin-bottom: 20px;
  }

  /* Grid of Variants */
  .grid-states {
    display: grid;
    grid-template-columns: 1fr;
    gap: 16px;
  }
  @media (min-width: 640px) {
    .grid-states {
      grid-template-columns: repeat(2, 1fr);
    }
  }
  @media (min-width: 1024px) {
    .grid-states {
      grid-template-columns: repeat(3, 1fr);
    }
  }

  .state-card {
    border: 1px solid var(--border-subtle);
    border-radius: 8px;
    padding: 16px;
    background: var(--bg-canvas);
    display: flex;
    flex-direction: column;
    gap: 12px;
  }
  .state-header {
    display: flex;
    align-items: baseline;
    justify-content: space-between;
  }
  .state-title {
    font-size: 12px;
    font-weight: 700;
    text-transform: uppercase;
    letter-spacing: 0.04em;
    color: var(--text-secondary);
  }
  .state-tier-tag {
    font-family: 'JetBrains Mono', monospace;
    font-size: 10px;
    padding: 2px 6px;
    border-radius: 4px;
  }
  .state-explanation {
    font-size: 12px;
    color: var(--text-secondary);
    line-height: 1.4;
  }

  /* ----------------------------------------------------
     COMPONENTS UNDER SPECIFICATION
     ---------------------------------------------------- */
  
  /* Variant A: Session Timer (In Exam Mode & Practice Mode) */
  .session-timer {
    display: inline-flex;
    align-items: center;
    gap: 8px;
    padding: 6px 12px;
    border-radius: 8px;
    font-variant-numeric: tabular-nums;
    transition: background-color 0.15s ease, border-color 0.15s ease, color 0.15s ease;
    user-select: none;
    min-height: 38px;
    position: relative;
  }

  /* Numeric Display */
  .timer-digits {
    font-family: 'JetBrains Mono', monospace;
    font-size: 14px;
    font-weight: 600;
    letter-spacing: 0.04em;
  }
  .timer-meta {
    display: flex;
    flex-direction: column;
    align-items: flex-start;
    line-height: 1.1;
  }
  .timer-label {
    font-size: 10px;
    font-weight: 600;
    text-transform: uppercase;
    letter-spacing: 0.05em;
  }
  .timer-mode-chip {
    font-size: 9px;
    font-weight: 600;
    letter-spacing: 0.02em;
    opacity: 0.85;
  }

  /* Phase 1: Normal (Running) */
  .session-timer.phase-normal {
    background: var(--bg-surface);
    border: 1px solid var(--border-strong);
    color: var(--text-primary);
  }
  .session-timer.phase-normal .timer-icon {
    color: var(--text-secondary);
  }

  /* Phase 2: Warning (Last Quarter) -> Amber, Bold weight, Distinct Hourglass/Alert */
  .session-timer.phase-warning {
    background: var(--warning-bg);
    border: 1.5px solid var(--warning-border);
    color: var(--warning-amber);
  }
  .session-timer.phase-warning .timer-digits {
    font-weight: 700;
  }

  /* Phase 3: Critical (Last 5 minutes) -> Crimson, Thicker border, Distinct Flag/Alert, Calm non-flashing */
  .session-timer.phase-critical {
    background: var(--critical-bg);
    border: 2px solid var(--critical-border);
    color: var(--critical-crimson);
  }
  .session-timer.phase-critical .timer-digits {
    font-weight: 700;
  }

  /* Paused State (Only allowed in Practice Mode) */
  .session-timer.state-paused {
    background: var(--neutral-bg);
    border: 1px dashed var(--neutral-border);
    color: var(--neutral-gray);
  }

  /* Finished / Time Up State */
  .session-timer.state-finished {
    background: var(--bg-surface-subtle);
    border: 1px solid var(--border-subtle);
    color: var(--text-muted);
  }

  /* Interactive Pause Button (Practice mode only) */
  .timer-action-btn {
    appearance: none;
    border: none;
    background: transparent;
    cursor: pointer;
    display: inline-flex;
    align-items: center;
    justify-content: center;
    width: 28px;
    height: 28px;
    border-radius: 6px;
    color: inherit;
    transition: background 0.15s ease;
    margin-left: -2px;
  }
  .timer-action-btn:hover {
    background: rgba(0, 0, 0, 0.06);
  }


  .timer-action-btn:focus-visible {
    outline: 2px solid var(--focus-ring);
    outline-offset: 1px;
  }

  /* Exam Mode Badge (Disables Pause) */
  .exam-locked-pill {
    display: inline-flex;
    align-items: center;
    gap: 4px;
    font-size: 9px;
    font-weight: 700;
    text-transform: uppercase;
    background: rgba(0, 0, 0, 0.05);
    padding: 2px 5px;
    border-radius: 3px;
    color: inherit;
  }



  /* ----------------------------------------------------
     Variant B: User's Exam Date Countdown (Separate Case)
     ---------------------------------------------------- */
  .exam-date-countdown {
    background: var(--bg-surface);
    border: 1px solid var(--border-subtle);
    border-radius: 10px;
    padding: 14px 18px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 16px;
    box-shadow: var(--shadow-sm);
  }
  .countdown-info {
    display: flex;
    flex-direction: column;
    gap: 3px;
  }
  .countdown-meta-tag {
    font-family: 'JetBrains Mono', monospace;
    font-size: 10px;
    font-weight: 600;
    text-transform: uppercase;
    color: var(--text-muted);
    letter-spacing: 0.05em;
  }
  .countdown-title {
    font-size: 14px;
    font-weight: 600;
    color: var(--text-primary);
  }
  .countdown-user-date {
    font-size: 12px;
    color: var(--text-secondary);
  }
  .countdown-value-badge {
    text-align: right;
    display: flex;
    flex-direction: column;
    align-items: flex-end;
  }
  .countdown-days {
    font-family: 'JetBrains Mono', monospace;
    font-size: 22px;
    font-weight: 700;
    color: var(--brand-primary);
    line-height: 1;
    letter-spacing: -0.02em;
  }
  .countdown-days-sub {
    font-size: 11px;
    font-weight: 500;
    color: var(--text-secondary);
    margin-top: 3px;
  }

  /* Empty state: No Date Set */
  .exam-date-empty {
    border: 1px dashed var(--border-strong);
    background: var(--bg-canvas);
    border-radius: 10px;
    padding: 16px 18px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 16px;
  }
  .set-date-btn {
    height: 36px;
    padding: 0 14px;
    border-radius: 6px;
    background: var(--bg-surface);
    border: 1px solid var(--border-strong);
    color: var(--text-primary);
    font-size: 12px;
    font-weight: 600;
    display: inline-flex;
    align-items: center;
    gap: 6px;
    cursor: pointer;
    transition: all 0.15s ease;
    white-space: nowrap;
  }
  .set-date-btn:hover {
    background: var(--bg-surface-subtle);
  }
  .set-date-btn:focus-visible {
    outline: 2px solid var(--focus-ring);
    outline-offset: 2px;
  }

  /* Mockup Framing for 390px Mobile Top Bars */
  .mobile-mockup-wrapper {
    width: 390px;
    max-width: 100%;
    border: 1px solid var(--border-strong);
    border-radius: 16px;
    background: var(--bg-canvas);
    overflow: hidden;
    box-shadow: var(--shadow-md);
  }
  .mobile-status-bar {
    height: 38px;
    background: var(--bg-surface);
    border-bottom: 1px solid var(--border-subtle);
    padding: 0 16px;
    display: flex;
    align-items: center;
    justify-content: space-between;
    font-family: 'JetBrains Mono', monospace;
    font-size: 11px;
    font-weight: 600;
    color: var(--text-secondary);
  }
  .mobile-top-bar {
    background: var(--bg-surface);
    padding: 10px 14px;
    border-bottom: 1px solid var(--border-subtle);
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
  }
  .mobile-app-brand {
    display: flex;
    align-items: center;
    gap: 8px;
  }
  .mobile-app-icon {
    width: 26px;
    height: 26px;
    border-radius: 6px;
    background: var(--brand-primary);
    color: #FFFFFF;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: 700;
    font-size: 11px;
  }
  .mobile-exam-meta {
    display: flex;
    flex-direction: column;
  }
  .mobile-exam-meta span:first-child {
    font-size: 12px;
    font-weight: 700;
    color: var(--text-primary);
  }
  .mobile-exam-meta span:last-child {
    font-size: 10px;
    color: var(--text-muted);
  }

  .mobile-card-content {
    padding: 16px;
    font-family: 'Newsreader', serif;
    font-size: 14px;
    line-height: 1.5;
    color: var(--text-primary);
  }
  .mobile-card-content .clinical-tag {
    font-family: 'Plus Jakarta Sans', sans-serif;
    font-size: 11px;
    font-weight: 600;
    color: var(--brand-primary);
    margin-bottom: 6px;
    display: block;
  }

  /* Mockup Framing for Wide (1280px Desktop Header) */
  .desktop-mockup-wrapper {
    width: 100%;
    border: 1px solid var(--border-strong);
    border-radius: 12px;
    background: var(--bg-canvas);
    overflow: hidden;
    box-shadow: var(--shadow-md);
  }
  .desktop-top-bar {
    background: var(--bg-surface);
    padding: 12px 24px;
    border-bottom: 1px solid var(--border-subtle);
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 20px;
  }
  .desktop-meta-group {
    display: flex;
    align-items: center;
    gap: 16px;
  }
  .desktop-exam-title {
    font-size: 14px;
    font-weight: 700;
    color: var(--text-primary);
  }
  .desktop-progress-chip {
    font-family: 'JetBrains Mono', monospace;
    font-size: 12px;
    background: var(--bg-surface-subtle);
    padding: 4px 10px;
    border-radius: 6px;
    color: var(--text-secondary);
  }
  .desktop-right-group {
    display: flex;
    align-items: center;
    gap: 16px;
  }

  /* Comparison Matrix Table */
  .spec-table {
    width: 100%;
    border-collapse: collapse;
    font-size: 13px;
    margin-top: 12px;
  }
  .spec-table th, .spec-table td {
    padding: 10px 14px;
    text-align: left;
    border-bottom: 1px solid var(--border-subtle);
  }
  .spec-table th {
    font-weight: 600;
    color: var(--text-secondary);
    background: var(--bg-surface-subtle);
    font-size: 11px;
    text-transform: uppercase;
    letter-spacing: 0.04em;
  }
  .spec-table td:first-child {
    font-weight: 600;
    color: var(--text-primary);
  }

  /* Icon helper */
  .svg-icon {
    width: 16px;
    height: 16px;
    fill: none;
    stroke: currentColor;
    stroke-width: 2;
    stroke-linecap: round;
    stroke-linejoin: round;
    flex-shrink: 0;
  }

  /* Respect prefers-reduced-motion: zero flashing or pulsing */
  @media (prefers-reduced-motion: reduce) {
    *, ::before, ::after {
      animation-duration: 0.01ms !important;
      animation-iteration-count: 1 !important;
      transition-duration: 0.01ms !important;
    }
  }