/* App shell */
  .app { display: grid; grid-template-rows: auto 1fr auto; min-height: 100vh; }

  /* ───── Header ───── */
  header.bar {
    display: flex; align-items: center; gap: 24px;
    padding: 14px 24px;
    background: var(--panel);
    border-bottom: 1px solid var(--line);
  }
  .brand { display: flex; align-items: center; gap: 10px; }
  .brand-mark {
    width: 28px; height: 28px; border-radius: 7px;
    display: grid; place-items: center;
    background: #111827;
    overflow: hidden;
  }
  .brand-mark svg {
    width: 100%;
    height: 100%;
    display: block;
  }
  .brand-title { font-weight: 600; font-size: 15px; letter-spacing: -0.01em; }
  .brand-sub { color: var(--muted); font-size: 13px; margin-left: 2px; }

  .controls { flex: 1; display: flex; align-items: center; gap: 10px; flex-wrap: wrap; }
  .ctrl { display: flex; align-items: center; gap: 8px; }
  .ctrl-label { font-size: 12px; color: var(--muted); font-weight: 500; text-transform: uppercase; letter-spacing: 0.06em; }
  .language-control {
    position: relative;
    margin-left: auto;
  }
  .language-button {
    display: inline-flex;
    align-items: center;
    gap: 7px;
    background: var(--panel);
    border: 1px solid var(--line);
    border-radius: 8px;
    color: var(--ink-2);
    cursor: pointer;
    font: 600 13px 'JetBrains Mono', monospace;
    min-width: 58px;
    padding: 7px 10px;
    transition: background .12s, border-color .12s, color .12s;
  }
  .language-button:hover,
  .language-button.open {
    background: var(--bg-2);
    border-color: var(--line-2);
    color: var(--ink);
  }
  .language-button:focus-visible {
    outline: 2px solid var(--accent);
    outline-offset: 2px;
  }
  .language-flag {
    width: 20px;
    height: 12px;
    border-radius: 2px;
    box-shadow: 0 0 0 1px rgb(15 23 42 / 0.12), 0 1px 2px rgb(15 23 42 / 0.14);
    flex: 0 0 auto;
  }
  .language-chevron {
    width: 16px;
    height: 16px;
    color: var(--muted);
    margin-left: auto;
    transition: transform .16s ease;
  }
  .language-button.open .language-chevron {
    transform: rotate(180deg);
  }
  .language-menu {
    position: absolute;
    right: 0;
    top: calc(100% + 8px);
    z-index: 50;
    display: none;
    min-width: 150px;
    padding: 8px;
    background: var(--panel);
    border: 1px solid var(--line);
    border-radius: 12px;
    box-shadow: var(--shadow);
  }
  .language-menu.open {
    display: grid;
    gap: 4px;
  }
  .language-option {
    display: flex;
    align-items: center;
    gap: 9px;
    width: 100%;
    border: 0;
    border-radius: 8px;
    background: transparent;
    color: var(--ink);
    cursor: pointer;
    font: 700 13px 'JetBrains Mono', monospace;
    padding: 8px 9px;
    text-align: left;
  }
  .language-option:hover,
  .language-option.on {
    background: var(--accent-soft);
    color: var(--accent);
  }

  .seg {
    display: inline-flex; padding: 3px; gap: 2px;
    background: var(--bg-2); border: 1px solid var(--line); border-radius: 8px;
  }
  .seg button {
    background: transparent; border: 0; padding: 6px 12px; border-radius: 6px;
    font-weight: 600; font-size: 13px; color: var(--ink-2);
    transition: background .12s, color .12s;
    font-family: 'JetBrains Mono', monospace;
  }
  .seg button:hover { color: var(--ink); }
  .seg button.on {
    background: var(--ink); color: white;
  }

  .stepper { display: inline-flex; align-items: center; border: 1px solid var(--line); border-radius: 8px; overflow: hidden; background: var(--panel); }
  .stepper button {
    background: transparent; border: 0; padding: 6px 10px; font-weight: 600; color: var(--ink-2);
  }
  .stepper button:hover:not(:disabled) { background: var(--bg-2); color: var(--ink); }
  .stepper button:disabled { opacity: 0.35; cursor: not-allowed; }
  .stepper .val {
    min-width: 28px; text-align: center; font-family: 'JetBrains Mono', monospace; font-weight: 700;
    border-left: 1px solid var(--line); border-right: 1px solid var(--line);
    padding: 4px 8px; font-size: 13px;
  }

  .btn {
    background: var(--panel); border: 1px solid var(--line); border-radius: 8px;
    padding: 7px 14px; font-weight: 600; font-size: 13px; color: var(--ink);
    transition: all .12s;
  }
  .btn:hover:not(:disabled) { border-color: var(--line-2); background: var(--bg-2); }
  .btn:disabled {
    opacity: 0.38;
    cursor: not-allowed;
    box-shadow: none;
  }
  .btn-primary {
    background: var(--ink); color: white; border-color: var(--ink);
  }
  .btn-active {
    background: var(--good-soft); border-color: var(--good); color: var(--good);
  }
  .btn-check-ready {
    box-shadow: 0 0 0 3px var(--accent-soft);
  }
  .btn-primary:hover:not(:disabled) { background: oklch(0.30 0.025 260); }
  .btn-primary:disabled {
    background: var(--bg-2);
    border-color: var(--line);
    color: var(--muted);
  }
  .btn-ghost { background: transparent; border-color: transparent; color: var(--ink-2); }
  .btn-ghost:hover:not(:disabled) { background: var(--bg-2); color: var(--ink); }
  .btn-icon { margin-right: 4px; vertical-align: -2px; }

  /* ───── Main layout ───── */
  main {
    display: grid;
    grid-template-columns: minmax(0, 1fr) 10px var(--side-width, clamp(320px, 20vw, 420px));
    gap: 0;
    min-height: 0;
  }
  .stage {
    padding: 28px 28px 8px;
    overflow: auto;
    position: relative;
  }
  .side {
    border-left: 0;
    background: var(--panel);
    padding: 20px 14px;
    overflow: auto;
    display: flex; flex-direction: column; gap: 18px;
  }
  .side-resizer {
    position: relative;
    background: var(--panel);
    border-left: 1px solid var(--line);
    cursor: col-resize;
    touch-action: none;
  }
  .side-resizer::before {
    content: "";
    position: absolute;
    inset: 0 3px;
    border-radius: 999px;
    background: transparent;
    transition: background .12s;
  }
  .side-resizer:hover::before,
  .side-resizer:focus-visible::before,
  body.resizing-side .side-resizer::before {
    background: var(--line-2);
  }
  body.resizing-side {
    cursor: col-resize;
    user-select: none;
  }

  footer {
    display: flex;
    align-items: center;
    justify-content: space-between;
    gap: 18px;
  }
  .footer-links {
    display: inline-flex;
    align-items: center;
    gap: 6px;
    white-space: nowrap;
  }
  .footer-link {
    border: 0;
    background: transparent;
    padding: 0;
    color: var(--muted);
    font: inherit;
    text-decoration: none;
  }
  .footer-link:hover,
  .footer-link:focus-visible {
    color: var(--ink);
    text-decoration: underline;
    text-underline-offset: 2px;
  }