:root {
  color-scheme: light;
  --ink: #1f2937;
  --ink-deep: #0f172a;
  --muted: #6b7280;
  --paper: #f8fafc;
  --desk: #cfd4dc;
  --line: #9aa3b2;
  --line-thick: #475569;
  --accent: #2563eb;
  --accent-soft: #dbeafe;
  --danger: #dc2626;
  --good: #16a34a;
  --fixed: #0f172a;
  --user: #2563eb;
  --hi-peer: #eef2ff;
  --hi-same: #c7d2fe;
  --hi-sel: #bfdbfe;
  --hi-err: #fecaca;
}

* { box-sizing: border-box; }

html, body {
  overflow: hidden;
  overscroll-behavior: none;
  width: 100%;
  height: 100%;
}

body {
  margin: 0;
  min-height: 100svh;
  font-family: "Clear Sans", "Helvetica Neue", Arial, -apple-system, BlinkMacSystemFont, sans-serif;
  color: var(--ink);
  background: var(--paper);
  display: grid;
  place-items: start center;
  padding: max(14px, env(safe-area-inset-top)) 12px max(14px, env(safe-area-inset-bottom));
  touch-action: none;
  -webkit-user-select: none;
  user-select: none;
  position: fixed;
  inset: 0;
  overflow-y: auto;
}

.app {
  width: min(96vw, 520px);
  padding-top: 4px;
}

.topbar {
  display: flex;
  justify-content: space-between;
  align-items: flex-start;
  gap: 12px;
  margin-bottom: 12px;
  flex-wrap: wrap;
}

h1 {
  margin: 0;
  font-size: 34px;
  line-height: 1;
  font-weight: 800;
  color: var(--ink-deep);
  letter-spacing: -0.02em;
}

p { margin: 6px 0 0; color: var(--muted); font-size: 14px; }

.hud { display: flex; gap: 6px; }
.hudBox {
  min-width: 62px;
  padding: 7px 10px;
  border-radius: 8px;
  background: #fff;
  border: 1px solid var(--desk);
  text-align: center;
}
.hudBox span {
  display: block;
  color: var(--muted);
  font-size: 10px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  font-weight: 700;
}
.hudBox strong {
  display: block;
  margin-top: 2px;
  font-size: 16px;
  font-weight: 700;
  color: var(--ink-deep);
}

.difficulty {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 6px;
  margin: 0 0 12px;
}
.difficulty button {
  border: 1px solid var(--desk);
  background: #fff;
  color: var(--ink);
  padding: 9px 0;
  border-radius: 8px;
  font-weight: 700;
  font-size: 14px;
  cursor: pointer;
  transition: all 0.15s ease;
}
.difficulty button:hover { border-color: var(--accent); color: var(--accent); }
.difficulty button.active {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}

.boardShell {
  position: relative;
  width: 100%;
  aspect-ratio: 1;
  border-radius: 10px;
  padding: 4px;
  background: var(--line-thick);
  box-shadow: 0 10px 24px rgba(15, 23, 42, 0.12);
}

.board {
  width: 100%;
  height: 100%;
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  grid-template-rows: repeat(9, 1fr);
  gap: 0;
  background: var(--line);
  border-radius: 6px;
  overflow: hidden;
}

.cell {
  background: #fff;
  display: grid;
  place-items: center;
  cursor: pointer;
  position: relative;
  font-weight: 600;
  font-size: clamp(18px, 5.4vw, 30px);
  color: var(--user);
  border-right: 1px solid var(--desk);
  border-bottom: 1px solid var(--desk);
  transition: background 0.1s ease;
}

/* 3x3 宫的粗边框：每 3 列/行 */
.cell[data-col="2"],
.cell[data-col="5"] { border-right: 2px solid var(--line-thick); }
.cell[data-row="2"],
.cell[data-row="5"] { border-bottom: 2px solid var(--line-thick); }
.cell[data-col="8"] { border-right: 0; }
.cell[data-row="8"] { border-bottom: 0; }

.cell.fixed { color: var(--fixed); font-weight: 800; }
.cell.peer { background: var(--hi-peer); }
.cell.same { background: var(--hi-same); }
.cell.selected { background: var(--hi-sel); }
.cell.error { background: var(--hi-err); color: var(--danger) !important; }
.cell.error.same { background: #fbb4b4; }

.cell .notes {
  position: absolute;
  inset: 4%;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
  font-size: clamp(8px, 2vw, 11px);
  font-weight: 600;
  color: var(--muted);
  line-height: 1;
}
.cell .notes span { display: grid; place-items: center; }

.overlay {
  position: absolute;
  inset: 6px;
  border-radius: 8px;
  background: rgba(255, 255, 255, 0.94);
  display: grid;
  place-content: center;
  gap: 10px;
  text-align: center;
  backdrop-filter: blur(4px);
  padding: 20px;
}
.overlay strong { font-size: 30px; color: var(--good); font-weight: 800; }
.overlay p { color: var(--ink); font-size: 15px; margin: 0; }
.hidden { display: none; }

.pad {
  margin-top: 12px;
  display: grid;
  gap: 8px;
}
.numRow {
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  gap: 5px;
}
.numRow button {
  aspect-ratio: 1;
  border: 1px solid var(--desk);
  background: #fff;
  color: var(--ink-deep);
  font-weight: 800;
  font-size: clamp(16px, 4vw, 22px);
  border-radius: 8px;
  cursor: pointer;
  transition: all 0.1s ease;
  position: relative;
}
.numRow button:hover { background: var(--accent-soft); }
.numRow button:active { transform: translateY(1px); }
.numRow button.done {
  background: var(--desk);
  color: var(--muted);
}
.numRow button .rem {
  position: absolute;
  right: 3px;
  top: 2px;
  font-size: 9px;
  font-weight: 600;
  color: var(--muted);
}

.actionRow {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 6px;
}
.actionRow button {
  padding: 11px 0;
  border: 1px solid var(--desk);
  background: #fff;
  color: var(--ink);
  border-radius: 8px;
  font-weight: 700;
  font-size: 14px;
  cursor: pointer;
  transition: all 0.1s ease;
}
.actionRow button:hover { border-color: var(--accent); color: var(--accent); }
.actionRow button.active {
  background: var(--accent);
  color: #fff;
  border-color: var(--accent);
}

.controls {
  margin-top: 10px;
  display: grid;
}
.controls button {
  padding: 13px;
  border: 0;
  background: var(--accent);
  color: #fff;
  border-radius: 8px;
  font-weight: 800;
  font-size: 15px;
  cursor: pointer;
  letter-spacing: 0.04em;
}
.controls button:active { transform: translateY(1px); }

.beian-footer {
  width: min(520px, calc(100vw - 32px));
  margin: 18px auto 0;
  display: flex;
  flex-wrap: wrap;
  gap: 8px 14px;
  align-items: center;
  justify-content: center;
  color: var(--muted);
  font-size: 12px;
}

.beian-footer a {
  display: inline-flex;
  min-height: 28px;
  gap: 5px;
  align-items: center;
}

.beian-footer img {
  display: block;
  flex: none;
}

@media (max-width: 420px) {
  h1 { font-size: 28px; }
  .hudBox { min-width: 54px; padding: 6px 8px; }
  .hudBox strong { font-size: 14px; }
}