:root {
  --bg: #f2f4f8;
  --panel: #ffffff;
  --text: #1c2333;
  --text-muted: #6b7280;
  --border: #d7dbe4;
  --border-strong: #3c4356;
  --accent: #4f7cff;
  --accent-text: #ffffff;
  --given: #1c2333;
  --entered: #2f5fdc;
  --conflict: #e2483c;
  --selected: #cfe0ff;
  --peer: #eaf0ff;
  --same-value: #d3e2ff;
  --note: #6b7280;
  --success: #2fa25a;
  --shadow: 0 8px 24px rgba(20, 25, 40, 0.08);
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #12141c;
    --panel: #1a1d29;
    --text: #eef0f6;
    --text-muted: #9298ab;
    --border: #2c2f3d;
    --border-strong: #6b7180;
    --accent: #6c8fff;
    --accent-text: #0d1020;
    --given: #f2f3f8;
    --entered: #8fb0ff;
    --conflict: #ff6b60;
    --selected: #2a3a63;
    --peer: #202436;
    --same-value: #2c3c6c;
    --note: #9298ab;
    --success: #4ecb85;
    --shadow: 0 8px 24px rgba(0, 0, 0, 0.4);
  }
}

* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg);
  color: var(--text);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
}

.app {
  max-width: 980px;
  margin: 0 auto;
  padding: 20px 16px 60px;
}

.topbar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 12px;
  margin-bottom: 20px;
}

.logo {
  font-size: 26px;
  font-weight: 700;
  margin: 0;
  letter-spacing: 0.5px;
}

.topbar-controls {
  display: flex;
  align-items: center;
  gap: 12px;
  flex-wrap: wrap;
}

.field {
  display: flex;
  align-items: center;
  gap: 8px;
  font-size: 14px;
  color: var(--text-muted);
}

.field select {
  font-size: 14px;
  padding: 8px 10px;
  border-radius: 8px;
  border: 1px solid var(--border);
  background: var(--panel);
  color: var(--text);
}

.btn {
  font-size: 14px;
  font-weight: 600;
  padding: 10px 16px;
  border-radius: 10px;
  border: 1px solid var(--border);
  background: var(--panel);
  color: var(--text);
  cursor: pointer;
  transition: transform 0.05s ease, background 0.15s ease, border-color 0.15s ease;
}

.btn:hover {
  border-color: var(--accent);
}

.btn:active {
  transform: scale(0.97);
}

.btn-primary {
  background: var(--accent);
  border-color: var(--accent);
  color: var(--accent-text);
}

.btn-icon {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 4px;
  flex: 1;
  padding: 10px 6px;
}

.btn-icon .icon {
  font-size: 18px;
  line-height: 1;
}

.btn-icon.active {
  background: var(--accent);
  border-color: var(--accent);
  color: var(--accent-text);
}

.layout {
  display: flex;
  gap: 24px;
  align-items: flex-start;
  flex-wrap: wrap;
  justify-content: center;
}

.board-panel {
  position: relative;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 14px;
}

.stats {
  display: flex;
  gap: 20px;
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 10px 20px;
  box-shadow: var(--shadow);
}

.stat {
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 2px;
  min-width: 56px;
}

.stat-label {
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--text-muted);
}

.stat-value {
  font-size: 18px;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
}

.board {
  --cell: min(9vw, 56px);
  display: grid;
  grid-template-columns: repeat(9, var(--cell));
  grid-template-rows: repeat(9, var(--cell));
  background: var(--border-strong);
  gap: 1px;
  border: 3px solid var(--border-strong);
  border-radius: 8px;
  overflow: hidden;
  box-shadow: var(--shadow);
  user-select: none;
}

.cell {
  background: var(--panel);
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  font-size: calc(var(--cell) * 0.5);
  font-weight: 500;
  color: var(--entered);
  cursor: pointer;
}

.cell.given {
  color: var(--given);
  font-weight: 700;
  cursor: default;
}

.cell.conflict {
  color: var(--conflict);
}

.cell.selected {
  background: var(--selected);
}

.cell.peer {
  background: var(--peer);
}

.cell.same-value {
  background: var(--same-value);
}

.cell.hinted {
  animation: pop 0.35s ease;
}

@keyframes pop {
  0% { transform: scale(1.35); }
  100% { transform: scale(1); }
}

/* thicker borders every 3rd row/col to show 3x3 boxes */
.cell[data-col="2"], .cell[data-col="5"] {
  border-right: 2px solid var(--border-strong);
}
.cell[data-col="3"], .cell[data-col="6"] {
  border-left: 2px solid var(--border-strong);
}
.cell[data-row="2"], .cell[data-row="5"] {
  border-bottom: 2px solid var(--border-strong);
}
.cell[data-row="3"], .cell[data-row="6"] {
  border-top: 2px solid var(--border-strong);
}

.notes-grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
  width: 100%;
  height: 100%;
  padding: 2px;
}

.notes-grid span {
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: calc(var(--cell) * 0.22);
  font-weight: 600;
  color: var(--note);
}

.win-banner {
  position: absolute;
  inset: 0;
  display: flex;
  align-items: center;
  justify-content: center;
  background: rgba(10, 12, 20, 0.55);
  border-radius: 12px;
}

.win-banner.hidden {
  display: none;
}

.win-card {
  background: var(--panel);
  border-radius: 16px;
  padding: 28px 32px;
  text-align: center;
  box-shadow: var(--shadow);
}

.win-card h2 {
  margin: 0 0 8px;
  color: var(--success);
}

.win-card p {
  margin: 0 0 16px;
  color: var(--text-muted);
}

.side-panel {
  width: 280px;
  display: flex;
  flex-direction: column;
  gap: 14px;
}

.action-row {
  display: flex;
  gap: 8px;
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 12px;
  padding: 8px;
  box-shadow: var(--shadow);
}

.numpad {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 8px;
}

.num-btn {
  aspect-ratio: 1;
  font-size: 24px;
  font-weight: 700;
  border-radius: 10px;
  border: 1px solid var(--border);
  background: var(--panel);
  color: var(--text);
  cursor: pointer;
  position: relative;
  box-shadow: var(--shadow);
}

.num-btn:hover {
  border-color: var(--accent);
  color: var(--accent);
}

.num-btn:active {
  transform: scale(0.96);
}

.num-btn.depleted {
  opacity: 0.35;
}

.num-btn .remaining {
  position: absolute;
  bottom: 3px;
  right: 6px;
  font-size: 10px;
  font-weight: 600;
  color: var(--text-muted);
}

.hint-text {
  font-size: 13px;
  color: var(--text-muted);
  line-height: 1.5;
  padding: 0 4px;
}

@media (max-width: 640px) {
  .board {
    --cell: min(10vw, 40px);
  }
  .side-panel {
    width: 100%;
    max-width: 360px;
  }
}