:root {
  --paper: #f7f5f0;
  --paper-line: #e7e2d6;
  --ink: #24292e;
  --ink-soft: #5b6470;
  --rule: #1f2933;
  --accent: #3a5a78;
  --accent-soft: #dce6ee;
  --mistake: #b3261e;
  --mistake-soft: #f6dedd;
  --success: #2f6f4e;
  --success-soft: #dcece3;
  --given: #24292e;
  --radius: 6px;
}

* { box-sizing: border-box; }

html, body {
  height: 100%;
}

body {
  margin: 0;
  background:
    repeating-linear-gradient(
      transparent, transparent 27px, var(--paper-line) 28px
    ),
    var(--paper);
  color: var(--ink);
  font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, Helvetica, Arial, sans-serif;
  -webkit-font-smoothing: antialiased;
}

.wrap {
  max-width: 480px;
  margin: 0 auto;
  padding: 20px 16px 40px;
  min-height: 100%;
  display: flex;
  flex-direction: column;
}

/* Header */

.topbar {
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 12px;
  margin-bottom: 18px;
}

.brand {
  display: flex;
  align-items: center;
  gap: 12px;
}

.brand-mark {
  width: 30px;
  height: 30px;
  color: var(--rule);
  flex-shrink: 0;
}

h1 {
  font-size: 1.15rem;
  margin: 0;
  letter-spacing: 0.01em;
}

.tagline {
  margin: 2px 0 0;
  font-size: 0.82rem;
  color: var(--ink-soft);
}

.difficulty-badge {
  font-size: 0.7rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  padding: 4px 9px;
  border-radius: 999px;
  border: 1px solid var(--rule);
  color: var(--rule);
  white-space: nowrap;
  margin-top: 2px;
}
.difficulty-badge[data-level="easy"] { border-color: var(--success); color: var(--success); }
.difficulty-badge[data-level="medium"] { border-color: var(--accent); color: var(--accent); }
.difficulty-badge[data-level="hard"] { border-color: var(--mistake); color: var(--mistake); }

/* Stat row */

.stat-row {
  display: flex;
  align-items: center;
  gap: 10px;
  margin-bottom: 16px;
}

.stat {
  background: #fff;
  border: 1px solid var(--paper-line);
  border-radius: var(--radius);
  padding: 7px 14px;
  display: flex;
  flex-direction: column;
  align-items: center;
  min-width: 84px;
}

.stat-label {
  font-size: 0.65rem;
  text-transform: uppercase;
  letter-spacing: 0.08em;
  color: var(--ink-soft);
}

.stat-value {
  font-variant-numeric: tabular-nums;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 1.05rem;
  font-weight: 600;
}

#mistakesDisplay.at-limit { color: var(--mistake); }

.btn-ghost {
  margin-left: auto;
  background: none;
  border: 1px solid var(--rule);
  color: var(--rule);
  padding: 8px 14px;
  border-radius: var(--radius);
  font-size: 0.85rem;
  cursor: pointer;
}
.btn-ghost:hover { background: var(--rule); color: var(--paper); }

.btn-primary {
  background: var(--rule);
  color: var(--paper);
  border: 1px solid var(--rule);
  padding: 10px 18px;
  border-radius: var(--radius);
  font-size: 0.9rem;
  font-weight: 600;
  cursor: pointer;
}
.btn-primary:hover { background: var(--accent); border-color: var(--accent); }

/* Board */

.board-area {
  display: flex;
  justify-content: center;
  margin-bottom: 18px;
}

.board {
  display: grid;
  grid-template-columns: repeat(9, 1fr);
  grid-template-rows: repeat(9, 1fr);
  width: min(100%, 420px);
  aspect-ratio: 1 / 1;
  background: #fff;
  border: 2.5px solid var(--rule);
  border-radius: 2px;
}

.cell {
  display: flex;
  align-items: center;
  justify-content: center;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: clamp(15px, 4.2vw, 20px);
  font-weight: 500;
  border: 1px solid #d7d2c4;
  color: var(--accent);
  cursor: pointer;
  user-select: none;
  background: #fff;
  position: relative;
  transition: background 0.12s ease;
}

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

.cell:nth-child(3n) { border-right: 2px solid var(--rule); }
.cell:nth-child(9n+1) { border-left: 2px solid var(--rule); }
.cell:nth-child(n+19):nth-child(-n+27),
.cell:nth-child(n+46):nth-child(-n+54) { border-bottom: 2px solid var(--rule); }
.board .cell:nth-child(-n+9) { border-top: 2px solid var(--rule); }
.board .cell:nth-child(n+73) { border-bottom: 2px solid var(--rule); }

.cell.selected { background: var(--accent-soft); }
.cell.peer { background: #f1eee6; }
.cell.mistake {
  background: var(--mistake-soft);
  color: var(--mistake);
  animation: shake 0.25s ease;
}
.cell.complete { background: var(--success-soft); }

@keyframes shake {
  0%, 100% { transform: translateX(0); }
  25% { transform: translateX(-3px); }
  75% { transform: translateX(3px); }
}

/* Number pad */

.numpad {
  display: grid;
  grid-template-columns: repeat(5, 1fr);
  gap: 8px;
  max-width: 420px;
  margin: 0 auto;
}

.numpad button {
  padding: 12px 0;
  font-size: 1.05rem;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  border-radius: var(--radius);
  border: 1px solid var(--paper-line);
  background: #fff;
  color: var(--ink);
  cursor: pointer;
}
.numpad button:active { background: var(--accent-soft); }
.numpad button.erase { color: var(--ink-soft); font-family: inherit; }

.hint {
  text-align: center;
  font-size: 0.78rem;
  color: var(--ink-soft);
  margin: 16px 0 0;
}

.footer {
  margin-top: auto;
  padding-top: 24px;
  text-align: center;
}
.footer p {
  font-size: 0.72rem;
  color: var(--ink-soft);
  max-width: 360px;
  margin: 0 auto;
}

/* Modals */

.modal-backdrop {
  position: fixed;
  inset: 0;
  background: rgba(31, 41, 51, 0.55);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 20px;
  z-index: 10;
}
.modal-backdrop[hidden] { display: none; }

.modal {
  background: var(--paper);
  border: 1px solid var(--rule);
  border-radius: 8px;
  padding: 24px;
  max-width: 340px;
  width: 100%;
  text-align: center;
}
.modal h2 { margin: 0 0 8px; font-size: 1.15rem; }
.modal p { color: var(--ink-soft); font-size: 0.88rem; margin: 0 0 18px; }

.win-stats {
  display: flex;
  justify-content: space-between;
  margin: 0 0 20px;
  gap: 8px;
}
.win-stats > div {
  flex: 1;
  background: #fff;
  border: 1px solid var(--paper-line);
  border-radius: var(--radius);
  padding: 10px 4px;
}
.win-stats dt {
  font-size: 0.63rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--ink-soft);
}
.win-stats dd {
  margin: 4px 0 0;
  font-weight: 700;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
}

.modal-actions {
  display: flex;
  flex-direction: column;
  gap: 10px;
}

@media (prefers-reduced-motion: reduce) {
  .cell.mistake { animation: none; }
}

@media (max-width: 380px) {
  .stat { min-width: 72px; padding: 6px 10px; }
}