* { box-sizing: border-box; }
  :root {
    --sidebar-width: 400px;
    --app-bg: #0b0d10;
    --preview-bg: #050607;
    --checker-bg: #07090c;
    --checker-tile: #171c24;
    color-scheme: dark;
  }
  html { background: var(--app-bg); color-scheme: dark; }
  body {
    margin: 0;
    overflow: hidden;
    font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
    background: var(--app-bg);
    color: #e0e0e0;
  }
  #app { display: flex; flex-direction: column; height: 100vh; }

  /* Tabs */
  #tabs {
    display: flex;
    background: #222;
    border-bottom: 1px solid #444;
    padding: 4px 8px 0;
    gap: 4px;
    align-items: center;
  }
  .tab {
    padding: 8px 16px;
    cursor: pointer;
    background: #333;
    border-radius: 4px 4px 0 0;
    font-size: 13px;
    user-select: none;
    display: flex;
    align-items: center;
    gap: 8px;
  }
  .tab.active { background: #444; font-weight: 600; border-bottom: 2px solid #4a9eff; }
  .tab:hover { background: #3f3f3f; }
  .tab-close {
    background: none; border: none; color: #aaa; cursor: pointer; font-size: 14px; padding: 0; margin: 0;
    width: 16px; height: 16px; display: flex; align-items: center; justify-content: center; border-radius: 2px;
  }
  .tab-close:hover { background: #555; color: #fff; }
  #tab-add { padding: 8px 12px; font-weight: bold; font-size: 16px; line-height: 1; }

  /* Main */
  #main {
    flex: 1;
    position: relative;
    overflow: hidden;
    display: flex;
    align-items: center;
    justify-content: center;
  }

  /* Canvas Area */
  #canvas-container {
    position: absolute;
    top: 0;
    right: var(--sidebar-width);
    bottom: 0;
    left: 0;
    display: flex;
    align-items: flex-start;
    justify-content: flex-start;
    overflow: auto;
    padding: 24px;
    background: var(--preview-bg);
    color-scheme: dark;
    forced-color-adjust: none;
    overscroll-behavior: contain;
    -webkit-overflow-scrolling: touch;
  }
  #canvas-container.checkerboard {
    background-color: var(--checker-bg);
    background-image:
      linear-gradient(45deg, var(--checker-tile) 25%, transparent 25%),
      linear-gradient(-45deg, var(--checker-tile) 25%, transparent 25%),
      linear-gradient(45deg, transparent 75%, var(--checker-tile) 75%),
      linear-gradient(-45deg, transparent 75%, var(--checker-tile) 75%);
    background-size: 20px 20px;
    background-position: 0 0, 0 10px, 10px -10px, -10px 0px;
  }
  canvas {
    display: block;
    width: 512px;
    height: 512px;
    max-width: calc(100vw - var(--sidebar-width) - 60px);
    max-height: calc(100vh - 60px);
    image-rendering: pixelated;
    flex: 0 0 auto;
    margin: auto;
  }

  /* Gizmo overlay canvas - covers full container */
  #gizmo-canvas {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
    pointer-events: auto;
    touch-action: none;
    user-select: none;
    z-index: 10;
  }

  /* Sidebar */
  #sidebar {
    position: absolute;
    right: 0;
    top: 0;
    bottom: 0;
    z-index: 20;
    width: var(--sidebar-width);
    background: #252525;
    border-left: 1px solid #444;
    display: flex;
    flex-direction: column;
    overflow: hidden;
  }
  #layers-header {
    padding: 12px;
    border-bottom: 1px solid #444;
    font-weight: 600;
    display: flex;
    justify-content: space-between;
    align-items: center;
    font-size: 14px;
  }
  #layer-controls { display: flex; gap: 6px; align-items: center; }
  #layers-list {
    flex: 1;
    overflow-y: auto;
    padding: 8px;
    display: flex;
    flex-direction: column;
    gap: 4px;
  }
  .layer-item {
    background: #333;
    padding: 10px;
    border-radius: 6px;
    cursor: pointer;
    display: flex;
    align-items: center;
    gap: 10px;
    border: 2px solid transparent;
    transition: background 0.1s;
    will-change: transform;
  }
  .layer-item:hover { background: #3a3a3a; }
  .layer-item.selected { border-color: #4a9eff; background: #3a3a3a; }
  .layer-ghost {
    position: fixed;
    z-index: 1000;
    pointer-events: none;
    opacity: 0.95;
    box-shadow: 0 8px 24px rgba(0,0,0,0.5);
    background: #3a3a3a;
    border: 2px solid #4a9eff;
    border-radius: 6px;
    padding: 10px;
    display: flex;
    align-items: center;
    gap: 10px;
  }
  .layer-placeholder {
    border: 2px dashed #555;
    border-radius: 6px;
    background: transparent;
    width: 100%;
    flex-shrink: 0;
  }
  .drag-handle {
    cursor: grab;
    color: #888;
    font-size: 14px;
    user-select: none;
  }
  .drag-handle:active { cursor: grabbing; }
  .layer-info {
    flex: 1;
    font-size: 13px;
    display: flex;
    flex-direction: column;
    gap: 2px;
  }
  .layer-type { font-weight: 500; color: #fff; }
  .layer-meta { font-size: 11px; color: #888; }
  .layer-blend {
    background: #444;
    color: #eee;
    border: 1px solid #555;
    padding: 2px 4px;
    border-radius: 4px;
    font-size: 11px;
    cursor: pointer;
  }
  .layer-visibility {
    background: none; border: none; color: #aab3bd; cursor: pointer; font-size: 14px;
    width: 24px; height: 24px; display: flex; align-items: center; justify-content: center; border-radius: 4px;
  }
  .layer-visibility:hover { background: #444; }
  .layer-visibility.hidden { color: #626b75; }
  .layer-visibility svg {
    display: block;
    fill: none;
    stroke: currentColor;
    stroke-width: 1.8;
    stroke-linecap: round;
    stroke-linejoin: round;
  }

  /* Params Panel */
  #params-panel {
    padding: 12px;
    border-top: 1px solid #444;
    max-height: 320px;
    overflow-y: auto;
    background: #2a2a2a;
  }
  #params-title { font-weight: 600; font-size: 13px; margin-bottom: 10px; color: #ccc; }
  .param-row { display: flex; align-items: center; margin-bottom: 10px; gap: 8px; }
  .param-row label { width: 70px; font-size: 12px; color: #aaa; flex-shrink: 0; }
  .param-row input[type="range"] { flex: 1; cursor: pointer; }
  .param-row input[type="number"] {
    width: 80px; background: #333; color: #eee; border: 1px solid #555;
    padding: 4px; border-radius: 4px; font-size: 12px;
  }
  .param-row input[type="number"]:focus { outline: 1px solid #4a9eff; border-color: #4a9eff; }

  /* Export Controls */
  #export-controls {
    padding: 12px;
    border-top: 1px solid #444;
    display: flex;
    flex-direction: column;
    gap: 10px;
    background: #252525;
  }
  .control-row { display: flex; gap: 8px; align-items: center; justify-content: space-between; }
  .control-row label,
  .control-label { font-size: 12px; color: #aaa; flex-shrink: 0; }
  input { color-scheme: dark; }
  select {
    background: #333; color: #eee; border: 1px solid #555;
    padding: 4px 6px; border-radius: 4px; font-size: 12px;
    color-scheme: dark;
  }
  .segmented-control {
    display: flex;
    justify-content: flex-end;
    gap: 2px;
    background: #1d1d1d;
    border: 1px solid #555;
    border-radius: 6px;
    padding: 2px;
    min-width: 0;
  }
  .segmented-control button {
    background: transparent;
    color: #bbb;
    border-radius: 4px;
    padding: 5px 8px;
    font-size: 12px;
    font-weight: 500;
    white-space: nowrap;
  }
  .segmented-control button:hover { background: #333; color: #fff; }
  .segmented-control button.active {
    background: #4a9eff;
    color: #fff;
  }
  .size-options button { min-width: 38px; }
  .zoom-options button { min-width: 34px; }
  button {
    background: #4a9eff; color: white; border: none;
    padding: 8px 12px; border-radius: 4px; cursor: pointer; font-size: 13px; font-weight: 500;
    transition: background 0.15s;
    color-scheme: dark;
  }
  button:hover { background: #3a8eef; }
  button.secondary { background: #444; }
  button.secondary:hover { background: #555; }
  button.danger { background: #e74c3c; }
  button.danger:hover { background: #c0392b; }
  .btn-row { display: flex; gap: 8px; }
  .btn-row button { flex: 1; }

  /* Scrollbar */
  ::-webkit-scrollbar { width: 6px; height: 6px; }
  ::-webkit-scrollbar-track { background: #222; }
  ::-webkit-scrollbar-thumb { background: #555; border-radius: 3px; }
  ::-webkit-scrollbar-thumb:hover { background: #666; }
  ::-webkit-scrollbar-corner { background: #222; }

  /* Empty state */
  .empty-state { color: #888; font-size: 12px; font-style: italic; text-align: center; padding: 16px; }
  .webgl-error {
    position: absolute;
    z-index: 20;
    max-width: 360px;
    background: rgba(20, 20, 20, 0.9);
    border: 1px solid #555;
    border-radius: 6px;
    color: #eee;
  }

  @media (max-width: 760px) {
    body { overflow: auto; }
    #app { height: auto; min-height: 100vh; }
    #tabs { overflow-x: auto; padding-bottom: 4px; }
    #main {
      display: flex;
      flex-direction: column;
      align-items: stretch;
      justify-content: flex-start;
      overflow: visible;
    }
    #canvas-container {
      position: sticky;
      top: 0;
      right: auto;
      bottom: auto;
      left: auto;
      z-index: 30;
      min-height: 260px;
      height: min(100vw, 60vh);
      flex-shrink: 0;
      padding: 12px;
      border-bottom: 1px solid #444;
      box-shadow: 0 8px 24px rgba(0,0,0,0.35);
    }
    canvas {
      width: min(calc(100vw - 24px), 512px);
      height: min(calc(100vw - 24px), 512px);
      max-width: 100%;
      max-height: 60vh;
    }
    #sidebar {
      position: relative;
      right: auto;
      top: auto;
      bottom: auto;
      width: 100%;
      max-height: none;
      border-left: none;
      border-top: 1px solid #444;
    }
    #params-panel { max-height: none; }
    button,
    select { min-height: 44px; }
    .segmented-control { flex-wrap: wrap; }
    .segmented-control button { min-height: 40px; }
    .layer-visibility { width: 44px; height: 44px; }
  }