:root {
  color-scheme: light;
  --ink: #513c2e;
  --muted: #806e5e;
  --accent: #a64d18;
  --control-bg: #fae8d2;
  --control-soft: #faf0e4;
  --control-border: #edd7bf;
  --cell-size: 52px;
  font-family: "PingFang SC", "Microsoft YaHei", system-ui, sans-serif;
  color: var(--ink);
  background: #fbf7f0;
}
* { box-sizing: border-box; }
[hidden] { display: none !important; }
body {
  margin: 0;
  height: 100vh;
  height: 100dvh;
  display: flex;
  flex-direction: column;
  font-size: 15px;
  padding: env(safe-area-inset-top) env(safe-area-inset-right) env(safe-area-inset-bottom) env(safe-area-inset-left);
}
button, summary { -webkit-tap-highlight-color: transparent; touch-action: manipulation; }
button {
  min-width: 44px; min-height: 44px; padding: 8px 12px;
  border: 1px solid var(--control-border); border-radius: 10px;
  font: inherit; font-weight: 600; color: var(--ink); background: var(--control-bg); cursor: pointer;
}
button:disabled { opacity: .45; cursor: default; }
button:focus-visible, summary:focus-visible, canvas:focus-visible, textarea:focus-visible {
  outline: 3px solid #9d570a; outline-offset: 3px;
}
button.accent, button.active { background: var(--accent); border-color: var(--accent); color: #fff; }
button.quiet:not(.active) { background: var(--control-soft); }
@media (hover: hover) {
  button:not(:disabled):hover { filter: brightness(.94); }
  .cell:not(.fill):hover { background: #efd3ac; }
}
.app-header { flex: 0 0 auto; display: flex; align-items: center; justify-content: space-between; gap: 8px; padding: 8px 16px; }
h1, h2, h3, p { margin: 0; }
h1 { font-size: 20px; line-height: 1.3; }
h2 { font-size: 18px; }
h3 { font-size: 14px; }
.header-actions { display: flex; gap: 6px; flex: 0 0 auto; }
.build-toggle { display: flex; align-items: center; justify-content: center; gap: 4px; }
.toggle-indicator::after { content: "↓"; }
.build-toggle[aria-expanded="true"] .toggle-indicator::after { content: "↑"; }
.workspace {
  flex: 1 1 0; min-height: 0; display: grid;
  grid-template-areas: "build" "observation";
  grid-template-rows: auto minmax(232px, 1fr); gap: 12px; padding: 0 16px 16px;
}
.workspace.editor-collapsed { grid-template-areas: "observation"; grid-template-rows: minmax(232px, 1fr); }
.observation, .build-area {
  min-width: 0; background: #fff; border: 1px solid #e8e0d5; border-radius: 18px;
  padding: 10px; box-shadow: 0 6px 24px rgba(81, 60, 46, .04);
}
.observation { grid-area: observation; display: flex; flex-direction: column; gap: 6px; min-height: 232px; }
.observation-head { display: flex; align-items: center; justify-content: space-between; gap: 8px; flex: 0 0 auto; min-height: 32px; }
.status-line { display: flex; flex-wrap: wrap; align-items: baseline; gap: 4px 12px; font-size: 14px; }
.status-line > span { color: var(--muted); white-space: nowrap; }
.status-line b { color: var(--accent); font-size: 18px; }
.canvas-wrap { position: relative; flex: 1 1 auto; min-height: 112px; }
#canvas { position: absolute; inset: 0; }
#canvas canvas { width: 100%; height: 100%; display: block; touch-action: none; border-radius: 8px; }
.count-labels { position: absolute; inset: 0; pointer-events: none; overflow: hidden; }
.stack-count { position: absolute; display: flex; align-items: center; justify-content: center; transform: translate(-50%, -50%); border: 2px solid #246954; border-radius: 50%; background: rgba(255, 255, 255, .94); color: #18513e; font-weight: 700; line-height: 1; }
.observation-actions { display: flex; gap: 8px; flex: 0 0 auto; }
.view-buttons { flex: 1; display: grid; grid-template-columns: repeat(4, minmax(44px, 1fr)); gap: 4px; }
.view-btn { padding: 8px 4px; }
.gesture-hint { font-size: 12px; color: var(--muted); text-align: center; flex: 0 0 auto; line-height: 18px; }
.build-area { grid-area: build; align-self: start; background: #fff8ee; border-color: #ead6ba; }
.build-body { display: grid; gap: 6px; }
.layer-tabs { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 6px; }
.layer-tab { white-space: nowrap; padding: 8px 4px; }
.layer-tab span { display: inline-block; margin-left: 4px; font-size: 12px; opacity: .85; }
.layer-panels { display: flex; justify-content: center; gap: 12px; }
.layer-card { display: none; border: 2px solid transparent; border-radius: 14px; padding: 4px; background: #fff2df; }
.layer-card.active { display: block; border-color: #c58b52; }
.layer-card h3 { display: none; text-align: center; margin-bottom: 4px; }
.direction-label { text-align: center; font-size: 12px; color: var(--muted); line-height: 16px; }
.layer { display: grid; grid-template-columns: repeat(3, var(--cell-size)); gap: 4px; }
.cell { width: var(--cell-size); height: var(--cell-size); padding: 0; background: #f4e0c3; border: 1px solid #e4caa6; color: #fff; font-size: 24px; border-radius: 9px; }
.cell.fill { background: var(--accent); border-color: var(--accent); }
.more-tools { border-top: 1px solid #ecd8bd; }
summary { min-height: 44px; padding: 10px 8px; cursor: pointer; font-weight: 600; line-height: 24px; }
.tools-grid { display: grid; grid-template-columns: repeat(6, minmax(0, 1fr)); gap: 6px; padding: 8px 0; }
.tools-grid button { grid-column: span 2; padding: 8px 6px; font-size: 14px; }
.tools-grid button[aria-pressed] { grid-column: span 3; }
.more-tools p { color: var(--muted); font-size: 13px; line-height: 1.6; padding: 0 4px 6px; }
.scene-fallback { position: absolute; inset: 0; display: flex; flex-direction: column; align-items: center; justify-content: center; gap: 8px; padding: 12px; text-align: center; background: #f9f4eb; border-radius: 8px; }
.scene-fallback p { font-size: 13px; line-height: 1.5; max-width: 360px; }
.no-scene .canvas-wrap { min-height: 170px; }
dialog { width: min(480px, calc(100% - 24px)); max-height: calc(100dvh - 32px); padding: 20px; border: 1px solid #e8d2b5; border-radius: 18px; color: var(--ink); background: #fffaf2; overflow: auto; }
dialog::backdrop { background: rgba(63, 45, 25, .35); }
.dialog-head { display: flex; justify-content: space-between; align-items: center; gap: 8px; margin-bottom: 16px; }
dialog p { line-height: 1.8; margin: 12px 0; }
dialog label { display: block; margin: 12px 0 6px; font-weight: 600; }
textarea { width: 100%; font: inherit; font-size: 14px; padding: 10px; border: 1px solid #dbbd93; border-radius: 8px; background: #fff; resize: vertical; margin-bottom: 8px; }
code { font-size: 16px; overflow-wrap: anywhere; }
.sr-only { position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px; overflow: hidden; clip: rect(0,0,0,0); white-space: nowrap; border: 0; }
/* Keep the four header actions on one row even on narrow phones. */
@media (max-width: 599px) and (min-height: 601px), (max-width: 539px) {
  .app-header { flex-wrap: wrap; }
  .app-header h1 { width: 100%; }
  .header-actions { width: 100%; display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); }
}
@media (min-width: 640px) and (max-width: 959px) and (min-height: 601px) {
  :root { --cell-size: 56px; }
  .layer-card { display: block; }
  .layer-card h3 { display: block; text-align: center; margin-bottom: 4px; }
  .layer-tabs { max-width: 608px; margin: 0 auto; width: 100%; }
  .more-tools { max-width: 608px; width: 100%; margin: 0 auto; }
}
/* Wide windows and short landscape screens put the editor beside the scene. */
@media (min-width: 960px), (min-width: 540px) and (max-height: 600px) {
  .workspace { grid-template-areas: "observation build"; grid-template-columns: minmax(0, 1fr) 300px; grid-template-rows: minmax(232px, 1fr); }
  .build-area { max-height: 100%; overflow: auto; }
  .workspace.editor-collapsed { grid-template-columns: 1fr; grid-template-rows: minmax(232px, 1fr); }
  .toggle-indicator::after { content: "→"; }
  .build-toggle[aria-expanded="true"] .toggle-indicator::after { content: "←"; }
}
@media (max-width: 639px) {
  h1 { font-size: 18px; }
  .app-header { padding: 6px 10px; }
  .header-actions button { padding: 8px; }
  .workspace { gap: 8px; padding: 0 8px 8px; }
  .observation, .build-area { border-radius: 14px; padding: 8px; }
}
@media (max-height: 740px) {
  :root { --cell-size: 48px; }
  .gesture-hint { display: none; }
}
@media (min-width: 540px) and (max-width: 959px) and (max-height: 600px) {
  .app-header { padding: 4px 12px; }
  .workspace { gap: 8px; padding: 0 8px 8px; grid-template-columns: minmax(0, 1fr) 244px; }
  .build-area { padding: 8px; }
  .layer-card { padding: 0; }
  .build-body { grid-template-columns: minmax(156px, 1fr) 64px; gap: 4px; }
  .layer-panels { grid-column: 1; grid-row: 1; justify-content: flex-start; }
  .layer-tabs { grid-column: 2; grid-row: 1; grid-template-columns: 1fr; gap: 4px; }
  .more-tools { grid-column: 1 / -1; }
  .observation-actions > button { padding: 8px; }
}
/* Desktop sidebars show all three layers without a separate layer-selection step. */
@media (min-width: 960px) {
  .workspace { grid-template-columns: minmax(0, 1fr) 538px; }
  .build-area { --cell-size: 48px; }
  .layer-card { display: block; }
  .layer-card h3 { display: block; }
}
@media (min-width: 1200px) and (min-height: 741px) {
  .workspace { grid-template-columns: minmax(0, 1fr) 584px; }
  .build-area { --cell-size: 52px; }
}
@media (prefers-reduced-motion: no-preference) { button { transition: background-color .15s; } }