:root {
  --board-line: rgba(0, 0, 0, 0.12);
  --board-line-strong: rgba(0, 0, 0, 0.55);
  --cell-bg: #ffffff;
  --cell-fixed: #1d2733;
  --cell-user: #0d6efd;
  --cell-error: #dc3545;
  --cell-sel: #f08a8a;
  --cell-peer: #fbdada;
  --cell-same: #f3aeae;
  --cell-error-bg: #fbe3e5;
  --pad-bg: #f1f3f6;
}

[data-bs-theme="dark"] {
  --board-line: rgba(255, 255, 255, 0.14);
  --board-line-strong: rgba(255, 255, 255, 0.6);
  --cell-bg: #1a1d21;
  --cell-fixed: #e9ecef;
  --cell-user: #4dabff;
  --cell-error: #ff6b78;
  --cell-sel: #8a3a3a;
  --cell-peer: #3a2326;
  --cell-same: #6e2f32;
  --cell-error-bg: #4a2429;
  --pad-bg: #23272e;
}

* { -webkit-tap-highlight-color: transparent; }

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

body {
  background: var(--bs-body-bg);
  user-select: none;
  -webkit-user-select: none;
}

.app-shell {
  max-width: 520px;
  margin: 0 auto;
  min-height: 100%;
  min-height: 100dvh;
  display: flex;
  flex-direction: column;
  padding: env(safe-area-inset-top) 12px calc(env(safe-area-inset-bottom) + 8px);
}

/* Header */
.app-header { padding: 12px 4px 8px; }
.app-title {
  font-size: 1.35rem;
  font-weight: 700;
  letter-spacing: -0.02em;
}
.app-title i { color: var(--bs-primary); }
.btn-icon {
  border: none;
  background: transparent;
  color: var(--bs-secondary-color);
  font-size: 1.15rem;
  padding: 6px 9px;
  border-radius: 10px;
}
.btn-icon:hover, .btn-icon:focus { background: var(--pad-bg); color: var(--bs-body-color); }

/* Status bar */
.status-bar {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 6px;
  margin: 4px 0 12px;
}
.status-item {
  background: var(--pad-bg);
  border-radius: 12px;
  padding: 8px 4px;
  text-align: center;
}
.status-label {
  display: block;
  font-size: 0.62rem;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--bs-secondary-color);
}
.status-value {
  display: block;
  font-size: 1.05rem;
  font-weight: 700;
  font-variant-numeric: tabular-nums;
  margin-top: 1px;
}
.status-value.danger { color: var(--cell-error); }

/* Board */
.board-wrap {
  position: relative;
  width: 100%;
  margin-bottom: 14px;
}
.board {
  position: relative;
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  grid-template-rows: repeat(9, 1fr);
  aspect-ratio: 1 / 1;
  width: 100%;
  background: var(--board-line-strong);
  border: 2.5px solid var(--board-line-strong);
  border-radius: 10px;
  overflow: hidden;
  gap: 1px;
}
.cell {
  background: var(--cell-bg);
  display: flex;
  align-items: center;
  justify-content: center;
  position: relative;
  font-size: clamp(1.1rem, 6vw, 1.9rem);
  font-weight: 500;
  color: var(--cell-user);
  cursor: pointer;
  transition: background-color 0.08s ease;
}
/* thick 3x3 separators */
.cell[data-c="2"], .cell[data-c="5"] { margin-right: 1px; box-shadow: 2px 0 0 var(--board-line-strong); }
.cell[data-r="2"], .cell[data-r="5"] { margin-bottom: 1px; box-shadow: 0 2px 0 var(--board-line-strong); }
.cell[data-c="2"][data-r="2"], .cell[data-c="2"][data-r="5"],
.cell[data-c="5"][data-r="2"], .cell[data-c="5"][data-r="5"] {
  box-shadow: 2px 0 0 var(--board-line-strong), 0 2px 0 var(--board-line-strong);
}

.cell.fixed { color: var(--cell-fixed); font-weight: 700; }
.cell.error { color: var(--cell-error); background: var(--cell-error-bg); }
.cell.peer { background: var(--cell-peer); }
.cell.same { background: var(--cell-same); }
.cell.selected { background: var(--cell-sel); }
.cell.flash { animation: flash 0.4s ease; }
@keyframes flash { 0% { background: var(--cell-same); } 100% {} }

.cell .notes {
  position: absolute;
  inset: 0;
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
  font-size: clamp(0.42rem, 2.2vw, 0.65rem);
  font-weight: 600;
  color: var(--bs-secondary-color);
  line-height: 1;
}
.cell .notes span {
  display: flex;
  align-items: center;
  justify-content: center;
}

.board-overlay {
  position: absolute;
  inset: 0;
  background: var(--bs-body-bg);
  border-radius: 10px;
  display: flex;
  align-items: center;
  justify-content: center;
  z-index: 5;
  color: var(--bs-secondary-color);
}

/* Controls */
.controls { margin-top: auto; }
.control-row {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 6px;
  margin-bottom: 12px;
}
.action-btn {
  border: none;
  background: var(--pad-bg);
  border-radius: 12px;
  padding: 9px 2px;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 3px;
  font-size: 0.62rem;
  color: var(--bs-body-color);
  font-weight: 500;
}
.action-btn i { font-size: 1.25rem; }
.action-btn:active { transform: scale(0.95); }
.action-btn.active { background: var(--bs-primary); color: #fff; }
.action-btn:disabled { opacity: 0.4; }
.action-btn em { font-style: normal; opacity: 0.7; }

.numpad {
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  gap: 5px;
}
.num-btn {
  border: none;
  background: var(--pad-bg);
  border-radius: 10px;
  aspect-ratio: 1 / 1.25;
  font-size: clamp(1.1rem, 5vw, 1.6rem);
  font-weight: 600;
  color: var(--bs-primary);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  position: relative;
}
.num-btn:active { transform: scale(0.94); }
.num-btn .count {
  font-size: 0.55rem;
  font-weight: 500;
  color: var(--bs-secondary-color);
  line-height: 1;
}
.num-btn.done {
  color: var(--bs-secondary-color);
  opacity: 0.45;
}

.app-footer { padding-top: 14px; }

/* Toast */
.app-toast {
  position: fixed;
  left: 50%;
  bottom: calc(env(safe-area-inset-bottom) + 18px);
  transform: translateX(-50%) translateY(20px);
  background: var(--bs-emphasis-color);
  color: var(--bs-body-bg);
  padding: 10px 18px;
  border-radius: 999px;
  font-size: 0.85rem;
  font-weight: 500;
  opacity: 0;
  pointer-events: none;
  transition: opacity 0.2s, transform 0.2s;
  z-index: 1080;
  max-width: 90vw;
  text-align: center;
}
.app-toast.show { opacity: 1; transform: translateX(-50%) translateY(0); }

@media (max-width: 360px) {
  .action-btn span { font-size: 0.56rem; }
  .status-value { font-size: 0.95rem; }
}