* { box-sizing: border-box; }
  html, body { margin: 0; height: 100%; background: var(--bg); color: var(--text);
    font: 13px/1.4 "Segoe UI", system-ui, sans-serif; }
  button, input, select, textarea { font: inherit; color: var(--text);
    background: var(--panel2); border: 1px solid var(--border); border-radius: 4px; }
  button { cursor: pointer; padding: 5px 10px; }
  button:hover { border-color: var(--accent); }
  button:disabled { opacity: 0.4; cursor: default; border-color: var(--border); }
  button.primary { background: #2a3d5c; border-color: var(--accent); }
  button.danger { border-color: var(--danger); color: #ffc0cb; }
  button.is-busy,
  button.is-busy:disabled {
    opacity: 1;
    cursor: wait;
    pointer-events: none;
    min-width: var(--busy-min-w, 7.5rem);
    display: inline-flex;
    align-items: center;
    justify-content: center;
  }
  .btn-spinner {
    width: 14px;
    height: 14px;
    border: 2px solid rgba(232, 196, 138, 0.35);
    border-top-color: var(--mist-gold, #e8c48a);
    border-radius: 50%;
    animation: btn-spin 0.65s linear infinite;
  }
  @keyframes btn-spin {
    to { transform: rotate(360deg); }
  }
  input[type="number"], input[type="text"] { padding: 4px 6px; width: 72px; }
  input[type="text"].wide { width: 160px; }
  label { color: var(--muted); display: inline-flex; align-items: center; gap: 4px; }
  .row { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; }
  .gap { gap: 12px; }

  .app { display: grid; grid-template-rows: auto auto 1fr auto; height: 100%; min-height: 0; }
  header { padding: 10px 14px; border-bottom: 1px solid var(--border); background: var(--panel);
    display: flex; flex-wrap: wrap; gap: 12px; align-items: center; justify-content: space-between; }
  .brand { display: flex; align-items: center; gap: 12px; min-width: 0; }
  .brand-mark {
    flex: 0 0 auto; width: 48px; height: 48px; border-radius: 12px;
    background: #0a0a0a;
    border: 1px solid rgba(232, 196, 138, 0.35);
    box-shadow: 0 0 0 1px rgba(126, 184, 255, 0.08), 0 4px 14px rgba(0, 0, 0, 0.25);
    display: grid; place-items: center; overflow: hidden;
    user-select: none;
  }
  .brand-mark img {
    display: block; width: 100%; height: 100%;
    object-fit: cover; object-position: center;
    image-rendering: pixelated; image-rendering: crisp-edges;
  }
  header h1 { margin: 0; font-size: 17px; font-weight: 650; letter-spacing: 0.03em;
    font-family: "Segoe UI Semibold", "Segoe UI", system-ui, sans-serif; }
  header h1 .brand-sub {
    font-weight: 500; color: var(--mist-gold); letter-spacing: 0.08em;
    text-transform: uppercase; font-size: 12px; margin-left: 2px; vertical-align: 1px;
  }
  header .meta { color: var(--muted); font-size: 12px; margin-top: 2px; }
  .tabs { display: flex; gap: 2px; padding: 8px 12px 0; border-bottom: 1px solid var(--border);
    background: var(--panel); overflow-x: auto; align-items: flex-end; }
  .tab-wrap {
    display: inline-flex; align-items: stretch; position: relative; flex: 0 0 auto;
  }
  .tab-wrap.active { z-index: 1; }
  .tab { padding: 8px 14px; border: 1px solid transparent; border-bottom: none;
    border-radius: 6px 6px 0 0; background: transparent; color: var(--muted);
    display: inline-flex; align-items: center; gap: 2px; }
  .tab-wrap.active .tab,
  .tab.active { background: var(--bg); color: var(--text); border-color: var(--border);
    position: relative; top: 1px; }
  .tab .badge { font-size: 10px; color: var(--accent2); margin-left: 4px; }
  .tab-label { max-width: 120px; overflow: hidden; text-overflow: ellipsis; white-space: nowrap; }
  .tab-rename {
    width: 96px; padding: 2px 4px; margin: -2px 0; font: inherit; color: var(--text);
    background: var(--panel2); border: 1px solid var(--accent); border-radius: 3px;
  }
  .tab-close {
    position: absolute; top: 2px; right: 2px; z-index: 2;
    width: 16px; height: 16px; padding: 0; line-height: 14px; font-size: 12px;
    border: none; border-radius: 3px; background: transparent; color: var(--muted);
    opacity: 0; transition: opacity 0.12s ease;
  }
  .tab-wrap:hover .tab-close,
  .tab-wrap.active .tab-close { opacity: 0.85; }
  .tab-close:hover { color: var(--danger); background: rgba(255, 80, 100, 0.12); opacity: 1; }
  .tab-wrap.has-close .tab { padding-right: 22px; }
  .tab-add {
    align-self: center; margin: 0 4px 4px; width: 28px; height: 28px; padding: 0;
    border-radius: 50%; border: 1px dashed var(--border); background: transparent;
    color: var(--accent2); display: inline-flex; align-items: center; justify-content: center;
    flex: 0 0 auto;
  }
  .tab-add:hover {
    border-style: solid; border-color: var(--accent); color: var(--accent);
    background: rgba(80, 140, 220, 0.12); box-shadow: 0 0 0 1px rgba(80, 140, 220, 0.2);
  }

  .main { display: grid; grid-template-columns: 1fr 320px; min-height: 0; min-width: 0; }
  @media (max-width: 980px) { .main { grid-template-columns: 1fr; } }

  .workspace { display: grid; grid-template-rows: auto 1fr auto; min-height: 0; min-width: 0; padding: 10px; gap: 10px; }
  .sheet-bar { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; }
  .zoom-controls { display: inline-flex; align-items: center; gap: 2px; margin-left: 4px; }
  .zoom-controls button { min-width: 32px; padding: 4px 8px; }
  #btnZoomLabel { min-width: 52px; font-variant-numeric: tabular-nums; }
  .sheet-row {
    --preview-pane-w: 340px;
    display: flex;
    flex-direction: row;
    align-items: stretch;
    gap: 0;
    min-height: 0;
    min-width: 0;
  }
  .sheet-stage {
    position: relative;
    flex: 1 1 auto;
    min-width: 160px;
    min-height: 0;
    overflow: auto;
    background: #0c0e12;
    border: 1px solid var(--border);
    border-radius: 6px;
  }
  .sheet-split {
    flex: 0 0 7px;
    margin: 0 3px;
    border-radius: 4px;
    background: transparent;
    cursor: col-resize;
    position: relative;
    touch-action: none;
  }
  .sheet-split::after {
    content: "";
    position: absolute;
    top: 12%;
    bottom: 12%;
    left: 2px;
    width: 3px;
    border-radius: 2px;
    background: var(--border);
    transition: background 0.12s ease, box-shadow 0.12s ease;
  }
  .sheet-split:hover::after,
  .sheet-split:focus-visible::after,
  body.resizing-panes .sheet-split::after {
    background: var(--mist-gold);
    box-shadow: 0 0 0 1px rgba(232, 196, 138, 0.25);
  }
  body.resizing-panes { cursor: col-resize !important; user-select: none !important; }
  .preview-dock {
    flex: 0 0 var(--preview-pane-w);
    width: var(--preview-pane-w);
    max-width: calc(100% - 180px);
    min-width: 240px;
    min-height: 0;
    display: flex;
    flex-direction: column;
    gap: 8px;
    align-self: stretch;
  }
  .preview-dock h2 { margin: 0; font-size: 12px; color: var(--muted); font-weight: 600;
    text-transform: uppercase; letter-spacing: 0.06em; flex-shrink: 0; }
  .preview-body {
    flex: 1 1 auto;
    min-height: 0;
    min-width: 0;
    display: flex;
    flex-direction: column;
    gap: 8px;
  }
  .preview-side {
    flex: 0 0 auto;
    display: flex;
    flex-direction: column;
    gap: 8px;
    min-width: 0;
  }
  /* Wide preview: canvas left, controls as a vertical rail on the right */
  .preview-dock-wide .preview-body {
    flex-direction: row;
    align-items: stretch;
  }
  .preview-dock-wide .preview-stage {
    flex: 1 1 auto;
    min-width: 0;
  }
  .preview-dock-wide .preview-side {
    flex: 0 0 148px;
    width: 148px;
    overflow-x: hidden;
    overflow-y: auto;
    padding-left: 2px;
    border-left: 1px solid var(--border);
    padding-left: 8px;
  }
  .preview-dock-wide .preview-dock-controls {
    flex-direction: column;
    align-items: stretch;
    flex-wrap: nowrap;
    gap: 6px;
  }
  .preview-dock-wide .preview-dock-controls > button,
  .preview-dock-wide .preview-dock-controls > label {
    width: 100%;
    justify-content: flex-start;
  }
  .preview-dock-wide .preview-dock-controls .zoom-controls {
    display: flex;
    width: 100%;
    justify-content: space-between;
  }
  .preview-dock-wide .preview-dock-controls .zoom-controls button {
    flex: 1 1 0;
  }
  .preview-dock-wide .preview-dock-status {
    flex-direction: column;
    align-items: stretch;
  }
  .preview-dock-wide #previewBg { width: 100%; }
  @media (max-width: 820px) {
    .sheet-row { flex-direction: column; }
    .sheet-split { display: none; }
    .sheet-stage { min-height: 220px; }
    .preview-dock {
      width: 100% !important;
      flex: 1 1 auto;
      max-width: none;
      min-height: 280px;
    }
    .preview-dock-wide .preview-body { flex-direction: column; }
    .preview-dock-wide .preview-side {
      flex: 0 0 auto;
      width: auto;
      border-left: none;
      padding-left: 0;
    }
    .preview-dock-wide .preview-dock-controls {
      flex-direction: row;
      flex-wrap: wrap;
      align-items: center;
    }
  }
  /* Checkerboard for chroma-keyed / native-alpha transparency */
  .sheet-stage.keyed {
    background-color: #c8c8d0;
    background-image:
      linear-gradient(45deg, #9a9aa8 25%, transparent 25%),
      linear-gradient(-45deg, #9a9aa8 25%, transparent 25%),
      linear-gradient(45deg, transparent 75%, #9a9aa8 75%),
      linear-gradient(-45deg, transparent 75%, #9a9aa8 75%);
    background-size: 16px 16px;
    background-position: 0 0, 0 8px, 8px -8px, -8px 0;
  }
  #sheetCanvas { display: block; cursor: crosshair; max-width: none; image-rendering: pixelated; }
  .sheet-stage.pick-chroma #sheetCanvas { cursor: crosshair; }
  .sheet-stage.add-point #sheetCanvas { cursor: cell; }
  .sheet-stage.panning #sheetCanvas { cursor: grab; }
  .sheet-stage.panning-drag #sheetCanvas { cursor: grabbing; }
  .sheet-stage.panning { user-select: none; }
  .chroma-row { display: flex; flex-wrap: wrap; align-items: center; gap: 8px; margin: 6px 0; }
  .chroma-row input[type="color"] {
    width: 42px; height: 28px; padding: 2px; cursor: pointer;
    border: 1px solid var(--border); border-radius: 4px; background: var(--panel2);
  }
  .chroma-row input[type="color"]::-webkit-color-swatch-wrapper { padding: 0; }
  .chroma-row input[type="color"]::-webkit-color-swatch { border: 1px solid var(--border); border-radius: 3px; }
  .chroma-row input:disabled,
  .nudge input:disabled {
    opacity: 0.45;
    cursor: default;
  }
  button.pick-active { border-color: var(--accent2); background: #2a4038; color: var(--accent2); }
  .hint { color: var(--muted); font-size: 12px; }
  .warn { color: var(--warn); }

  .timeline-wrap {
    border: 1px solid var(--border); border-radius: 6px; background: var(--panel);
    padding: 8px; min-width: 0; max-width: 100%; overflow: hidden;
  }
  .timeline-wrap h2 { margin: 0 0 6px; font-size: 12px; color: var(--muted); font-weight: 600;
    text-transform: uppercase; letter-spacing: 0.06em; }
  .timeline {
    display: flex; flex-wrap: nowrap; gap: 6px;
    overflow-x: auto; overflow-y: hidden;
    min-height: 92px; min-width: 0; max-width: 100%;
    padding-bottom: 6px;
    -webkit-overflow-scrolling: touch;
  }
  .tl-empty { color: var(--muted); align-self: center; padding: 12px; }
  .tl-cell { flex: 0 0 auto; width: 72px; border: 2px solid var(--border); border-radius: 4px;
    background: var(--panel2); cursor: grab; user-select: none; position: relative; }
  .tl-cell.selected { border-color: var(--sel); }
  .tl-cell.drag-over { border-color: var(--accent); }
  .tl-cell canvas { display: block; width: 68px; height: 68px; image-rendering: pixelated;
    background: #0a0c10; }
  .tl-cell .idx { position: absolute; top: 2px; left: 3px; font-size: 10px; background: #000a;
    padding: 0 3px; border-radius: 2px; }
  .tl-cell .src-id {
    position: absolute; bottom: 2px; right: 3px; font-size: 9px;
    background: #000a; padding: 0 3px; border-radius: 2px; color: #9cdcfe;
  }

  .side { border-left: 1px solid var(--border); background: var(--panel); padding: 10px;
    display: flex; flex-direction: column; gap: 12px; overflow: auto; min-height: 0; }
  .side h2 { margin: 0; font-size: 12px; color: var(--muted); font-weight: 600;
    text-transform: uppercase; letter-spacing: 0.06em; }
  .card { background: var(--panel2); border: 1px solid var(--border); border-radius: 6px;
    padding: 8px; display: flex; flex-direction: column; gap: 8px; }
  .preview-stage {
    flex: 1 1 0;
    min-height: 220px;
    overflow: auto;
    background: #0a0c10;
    border-radius: 4px;
    border: 1px solid var(--border);
    -webkit-overflow-scrolling: touch;
  }
  .preview-stage.panning { cursor: grab; user-select: none; }
  .preview-stage.panning-drag { cursor: grabbing; }
  .preview-stage.keyed,
  #previewCanvas.keyed {
    background-color: #c8c8d0;
    background-image:
      linear-gradient(45deg, #9a9aa8 25%, transparent 25%),
      linear-gradient(-45deg, #9a9aa8 25%, transparent 25%),
      linear-gradient(45deg, transparent 75%, #9a9aa8 75%),
      linear-gradient(-45deg, transparent 75%, #9a9aa8 75%);
    background-size: 12px 12px;
    background-position: 0 0, 0 6px, 6px -6px, -6px 0;
  }
  #previewCanvas {
    display: block;
    width: auto;
    height: auto;
    min-width: 100%;
    min-height: 100%;
    background: transparent;
    border: none;
    border-radius: 0;
    image-rendering: pixelated;
  }
  .preview-dock-controls {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    align-items: center;
  }
  .preview-dock-status {
    flex-shrink: 0;
    min-height: 1.2em;
    line-height: 1.2;
    display: flex; flex-wrap: wrap; gap: 10px; align-items: center;
  }
  .tl-dur-label { color: var(--muted); font-size: 12px; }
  .preview-frame {
    display: inline-block;
    font-variant-numeric: tabular-nums;
    font-family: ui-monospace, Consolas, "Courier New", monospace;
    white-space: nowrap;
    min-width: 11ch;
  }
  .preview-popout {
    position: fixed; inset: 0; z-index: 80;
    background: rgba(6, 8, 14, 0.72);
    display: flex; align-items: center; justify-content: center;
    padding: 24px;
  }
  .preview-popout[hidden] { display: none !important; }
  .preview-popout-panel {
    background: var(--panel);
    border: 1px solid var(--border);
    border-radius: 8px;
    box-shadow: 0 16px 48px rgba(0, 0, 0, 0.45);
    max-width: calc(100vw - 48px);
    max-height: calc(100vh - 48px);
    display: flex; flex-direction: column; min-width: 0; min-height: 0;
  }
  .preview-popout-bar input[type="number"] { width: 52px; }
  .preview-popout-stage {
    overflow: auto; padding: 16px;
    display: flex; align-items: center; justify-content: center;
    background: #0c0e12; min-height: 0;
  }
  #previewPopoutCanvas {
    display: block;
    image-rendering: pixelated;
    border: 1px solid var(--border);
    border-radius: 4px;
    background: #0a0c10;
    flex: 0 0 auto;
  }
  #previewPopoutCanvas.keyed {
    background-color: #c8c8d0;
    background-image:
      linear-gradient(45deg, #9a9aa8 25%, transparent 25%),
      linear-gradient(-45deg, #9a9aa8 25%, transparent 25%),
      linear-gradient(45deg, transparent 75%, #9a9aa8 75%),
      linear-gradient(-45deg, transparent 75%, #9a9aa8 75%);
    background-size: 12px 12px;
    background-position: 0 0, 0 6px, 6px -6px, -6px 0;
  }
  .nudge grid, .nudge { display: grid; grid-template-columns: repeat(2, 1fr); gap: 6px; }
  .nudge label { display: flex; justify-content: space-between; gap: 6px; }
  .nudge input { width: 64px; }
  textarea#exportBox { width: 100%; height: 160px; resize: vertical; font-family: ui-monospace, Consolas, monospace;
    font-size: 11px; line-height: 1.35; }
  footer { padding: 6px 12px; border-top: 1px solid var(--border); background: var(--panel);
    color: var(--muted); font-size: 11px; display: flex; gap: 10px 16px;
    flex-wrap: wrap; align-items: center; }
  .footer-help { flex: 1 1 12rem; min-width: 0; }
  .footer-status { flex: 1 1 8rem; min-width: 0; color: var(--text); }
  .footer-brand {
    margin-left: auto; flex: 0 0 auto; order: 99;
    color: var(--mist-gold); letter-spacing: 0.04em; opacity: 0.95;
    white-space: nowrap; padding-left: 8px;
  }
  .drop-zone { border: 1px dashed var(--border); border-radius: 6px; padding: 10px; text-align: center;
    color: var(--muted); cursor: pointer; }
  .drop-zone.drag { border-color: var(--accent); color: var(--accent); }
  input[type="file"] { display: none; }
  .status-ok { color: var(--accent2); }
  .status-bad { color: var(--danger); }