/* ── Center Canvas ── */
    #center {
      flex: 1;
      display: flex;
      flex-direction: column;
      overflow: hidden;
      background: var(--surface);
    }

    #canvas-wrap {
      flex: 1;
      position: relative;
      overflow: hidden;
      background: var(--surface);
    }

    #canvas-wrap::before {
      content: '';
      position: absolute;
      inset: 0;
      background-image: radial-gradient(circle, var(--outline-variant) 1px, transparent 1px);
      background-size: 28px 28px;
      opacity: 0.35;
      pointer-events: none;
      z-index: 0;
    }

    #cy {
      position: absolute;
      inset: 0;
      z-index: 1;
      background: transparent;
    }

    /* Empty state */
    #empty-state {
      position: absolute;
      inset: 0;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      gap: 1rem;
      z-index: 2;
      text-align: center;
      padding: 2rem;
    }

    .es-icon {
      width: 72px;
      height: 72px;
      background: var(--surface-low);
      border-radius: var(--radius-2xl);
      display: flex;
      align-items: center;
      justify-content: center;
      font-size: 2rem;
      box-shadow: var(--ambient-shadow);
    }

    .es-title {
      font-family: 'Manrope', sans-serif;
      font-size: 1.1rem;
      font-weight: 700;
      color: var(--on-surface);
    }

    .es-desc {
      font-size: 0.8rem;
      color: var(--outline);
      max-width: 220px;
      line-height: 1.5;
    }

    /* Canvas floating controls */
    .canvas-float {
      position: absolute;
      top: 12px;
      left: 50%;
      transform: translateX(-50%);
      z-index: 10;
      display: none;
    }

    .canvas-float.visible {
      display: block;
    }

    /* Ensure float-pill is visible in fullscreen */
    #canvas-wrap:fullscreen .canvas-float.visible,
    #canvas-wrap:-webkit-full-screen .canvas-float.visible {
      display: block;
      z-index: 9999;
    }

    .float-pill {
      display: flex;
      align-items: center;
      gap: 0.2rem;
      background: var(--surface-lowest);
      backdrop-filter: blur(16px);
      border-radius: var(--radius-full);
      padding: 0.35rem 0.7rem;
      box-shadow: var(--float-shadow);
      border: 1px solid var(--outline-variant);
    }

    .float-btn {
      width: 30px;
      height: 30px;
      border-radius: 50%;
      border: none;
      background: none;
      color: var(--on-surface-variant);
      font-size: 0.9rem;
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: center;
      transition: all var(--dur-fast);
    }

    .float-btn:hover {
      background: var(--surface-highest);
      color: var(--primary);
    }

    .float-btn svg {
      width: 15px;
      height: 15px;
    }

    .float-sep {
      width: 1px;
      height: 16px;
      background: var(--outline-variant);
      margin: 0 0.2rem;
      opacity: 0.5;
    }

    /* Zoom controls */
    .zoom-ctrl {
      position: absolute;
      bottom: 16px;
      right: 16px;
      z-index: 10;
      display: flex;
      flex-direction: column;
      gap: 0.3rem;
    }

    .zoom-btn {
      width: 32px;
      height: 32px;
      background: var(--surface-lowest);
      backdrop-filter: blur(12px);
      border: 1px solid var(--outline-variant);
      border-radius: var(--radius-md);
      color: var(--on-surface-variant);
      font-size: 1rem;
      cursor: pointer;
      display: flex;
      align-items: center;
      justify-content: center;
      transition: all var(--dur-fast);
      box-shadow: var(--lift-shadow);
    }

    .zoom-btn:hover {
      background: var(--surface-high);
      color: var(--primary);
    }

    /* Canvas badge */
    .canvas-badge {
      position: absolute;
      top: 32px;
      right: 120px;
      z-index: 10;
      background: rgba(0, 91, 191, 0.1);
      color: var(--primary);
      font-size: 0.68rem;
      font-weight: 700;
      text-transform: uppercase;
      letter-spacing: 0.08em;
      padding: 0.3rem 0.7rem;
      border-radius: var(--radius-full);
      display: none;
    }

    .canvas-badge.visible {
      display: block;
    }

    /* ε-closure popup */
    .closure-popup {
      position: absolute;
      background: var(--surface-lowest);
      border-radius: var(--radius-lg);
      padding: 0.8rem 1rem;
      box-shadow: var(--float-shadow);
      z-index: 20;
      display: none;
      min-width: 180px;
    }

    .closure-popup.visible {
      display: block;
      animation: fadeScaleIn var(--dur-fast) var(--ease-socialite);
    }

    .closure-title {
      font-family: 'Manrope', sans-serif;
      font-size: 0.78rem;
      font-weight: 700;
      color: var(--on-surface);
      margin-bottom: 0.3rem;
    }

    .closure-states {
      font-family: 'JetBrains Mono', monospace;
      font-size: 0.78rem;
      color: var(--primary);
      font-weight: 600;
    }

    /* ── Floating Canvas Legend ── */
    .canvas-legend {
      position: absolute;
      bottom: 24px;
      left: 24px;
      padding: 0.65rem 0.8rem;
      background: var(--surface);
      border: 1px solid var(--outline-variant);
      border-radius: var(--radius-lg);
      box-shadow: var(--float-shadow);
      z-index: 100;
      display: flex;
      flex-direction: column;
      gap: 0.4rem;
      opacity: 0.95;
      animation: slideInRight 0.4s var(--ease-socialite);
    }

    .cl-row {
      display: flex;
      align-items: center;
      gap: 0.6rem;
      font-size: 0.68rem;
      font-weight: 600;
      color: var(--on-surface-variant);
      letter-spacing: 0.02em;
    }

    .canvas-reset-wrap {
      position: absolute;
      top: 24px;
      right: 24px;
      z-index: 100;
    }

    .btn-canvas-reset {
      display: flex;
      align-items: center;
      gap: 0.5rem;
      padding: 0.6rem 1rem;
      background: var(--surface);
      color: var(--tertiary);
      border: 1.5px solid var(--outline-variant);
      border-radius: var(--radius-full);
      font-family: 'Inter', sans-serif;
      font-size: 0.75rem;
      font-weight: 700;
      cursor: pointer;
      box-shadow: var(--float-shadow);
      transition: all 0.2s var(--ease-socialite);
    }

    .btn-canvas-reset:hover {
      background: var(--surface-high);
      border-color: var(--tertiary);
      transform: translateY(-1px);
    }

    .cl-symbol {
      width: 18px;
      height: 18px;
      border-radius: 50%;
      background: white;
      border: 1px solid var(--outline);
    }

    .cl-symbol.start {
      border: 2.5px solid #4caf50;
      outline: 1px solid var(--outline);
      outline-offset: -2.5px;
    }

    .cl-symbol.final {
      border: 2.5px solid #f44336;
      outline: 1px solid var(--outline);
      outline-offset: -2.5px;
    }

    .cl-symbol.dead {
      border-style: dashed;
      opacity: 0.6;
    }

    .cl-divider {
      height: 1px;
      background: var(--outline-variant);
      margin: 0.1rem 0;
    }

    .cl-line {
      width: 18px;
      height: 2px;
      background: var(--outline);
    }

    .cl-line.dashed {
      background: none;
      border-top: 2px dashed var(--primary-container);
    }

    @keyframes fadeScaleIn {
      from {
        opacity: 0;
        transform: scale(0.9) translateY(-4px);
      }

      to {
        opacity: 1;
        transform: scale(1) translateY(0);
      }
    }

    /* Regex canvas display (shown on regex stage, post-generate) */
    #regex-canvas-display {
      position: absolute;
      inset: 0;
      display: flex;
      flex-direction: column;
      align-items: center;
      justify-content: center;
      gap: 1.5rem;
      z-index: 2;
      padding: 2rem;
    }

    .rcd-badge {
      font-size: 0.65rem;
      font-weight: 700;
      letter-spacing: 0.14em;
      text-transform: uppercase;
      color: var(--primary);
      background: rgba(0, 91, 191, 0.08);
      padding: 0.3rem 0.9rem;
      border-radius: var(--radius-full);
    }

    .rcd-regex-wrap {
      background: var(--surface-lowest);
      border-radius: var(--radius-2xl);
      padding: 2rem 3rem;
      box-shadow: var(--float-shadow);
      text-align: center;
      max-width: 600px;
      width: 100%;
    }

    .rcd-label {
      font-size: 0.68rem;
      font-weight: 700;
      letter-spacing: 0.1em;
      text-transform: uppercase;
      color: var(--outline);
      margin-bottom: 0.7rem;
    }

    .rcd-regex-str {
      font-family: 'JetBrains Mono', monospace;
      font-size: 2.2rem;
      font-weight: 700;
      color: var(--primary);
      letter-spacing: 0.08em;
      word-break: break-all;
      line-height: 1.2;
    }

    .rcd-pills {
      display: flex;
      flex-wrap: wrap;
      gap: 0.5rem;
      justify-content: center;
      margin-top: 1.2rem;
    }

    .rcd-pill {
      padding: 0.35rem 0.85rem;
      border-radius: var(--radius-full);
      font-size: 0.72rem;
      font-weight: 600;
      font-family: 'JetBrains Mono', monospace;
    }

    .rcd-pill.syms {
      background: rgba(0, 91, 191, 0.1);
      color: var(--primary);
    }

    .rcd-pill.ops {
      background: rgba(124, 58, 237, 0.1);
      color: #7c3aed;
    }

    .rcd-pill.postfix {
      background: rgba(0, 110, 28, 0.1);
      color: var(--secondary);
    }

    .rcd-desc {
      font-size: 0.82rem;
      color: var(--on-surface-variant);
      line-height: 1.6;
      font-style: italic;
      max-width: 480px;
      text-align: center;
    }

    .rcd-arrow-row {
      display: flex;
      align-items: center;
      gap: 0.6rem;
      font-size: 0.8rem;
      color: var(--outline);
    }

    .rcd-step {
      background: var(--surface-lowest);
      border-radius: var(--radius-xl);
      padding: 0.55rem 1.1rem;
      font-family: 'Manrope', sans-serif;
      font-size: 0.78rem;
      font-weight: 700;
      color: var(--on-surface);
      box-shadow: var(--lift-shadow);
    }