:root {
  --bg: #0b111c;
  --panel: rgba(14, 22, 36, 0.72);
  --text: #ecf0ff;
  --muted: rgba(236, 240, 255, 0.7);
  --border: rgba(236, 240, 255, 0.16);
  --accent: #38bdf8;
  --accent-2: #f97316;
  --danger: #f87171;
  --cell: rgba(255,255,255,0.07);
  --shadow: 0 26px 60px rgba(4, 8, 18, 0.45);
  --font-display: "Avenir Next", "Gill Sans", "Trebuchet MS", sans-serif;
  --font-body: "Avenir Next", "Gill Sans", "Trebuchet MS", sans-serif;
}

[data-theme="light"] {
  --bg: #f2f5f9;
  --panel: rgba(255, 255, 255, 0.82);
  --text: #0f172a;
  --muted: rgba(15, 23, 42, 0.7);
  --border: rgba(15, 23, 42, 0.14);
  --accent: #0ea5e9;
  --accent-2: #ea580c;
  --danger: #e11d48;
  --cell: rgba(15, 23, 42, 0.05);
  --shadow: 0 18px 40px rgba(15, 23, 42, 0.16);
}

* { box-sizing: border-box; }
body {
  margin: 0;
  font-family: var(--font-body);
  background:
    radial-gradient(900px 600px at 12% 12%, rgba(56, 189, 248, 0.2), transparent 60%),
    radial-gradient(700px 500px at 90% 18%, rgba(249, 115, 22, 0.14), transparent 60%),
    linear-gradient(160deg, rgba(15, 23, 42, 0.25), transparent 55%),
    var(--bg);
  color: var(--text);
  min-height: 100vh;
  position: relative;
}

body::before {
  content: '';
  position: fixed;
  inset: 0;
  background-image:
    radial-gradient(rgba(255, 255, 255, 0.08) 1px, transparent 1px);
  background-size: 18px 18px;
  opacity: 0.25;
  pointer-events: none;
}

.container {
  max-width: 920px;
  margin: 0 auto;
  padding: 18px 14px 40px;
  position: relative;
  z-index: 1;
  animation: fadeUp 0.6s ease-out;
}

.header {
  display: grid;
  gap: 8px;
  padding: 14px 14px 6px;
}

.title { margin: 0; font-size: 32px; letter-spacing: 0.4px; font-family: var(--font-display); }
.subtitle { margin: 0; color: var(--muted); }

.controls {
  margin-top: 12px;
  padding: 14px;
  background: linear-gradient(140deg, rgba(255, 255, 255, 0.08), rgba(255, 255, 255, 0.02));
  border: 1px solid var(--border);
  border-radius: 14px;
  box-shadow: var(--shadow);
}

.control-row {
  display: flex;
  gap: 12px;
  align-items: center;
  flex-wrap: wrap;
}

.label { color: var(--muted); font-size: 14px; }
.select {
  background: var(--cell);
  border: 1px solid var(--border);
  color: var(--text);
  padding: 8px 10px;
  border-radius: 10px;
  font-family: var(--font-body);
}

.button-row {
  display: flex;
  flex-wrap: wrap;
  gap: 10px;
  margin-top: 12px;
}

.btn {
  appearance: none;
  border: 1px solid var(--border);
  background: var(--cell);
  color: var(--text);
  padding: 10px 12px;
  border-radius: 12px;
  cursor: pointer;
  font-weight: 700;
  transition: transform 0.15s ease, box-shadow 0.2s ease, border-color 0.2s ease;
}
.btn.primary { border-color: rgba(56, 189, 248, 0.65); background: rgba(56, 189, 248, 0.2); box-shadow: 0 10px 22px rgba(56, 189, 248, 0.18); }
.btn.danger { border-color: rgba(248, 113, 113, 0.65); background: rgba(248, 113, 113, 0.12); }
.btn:disabled { opacity: 0.6; cursor: not-allowed; }
.btn:hover { transform: translateY(-1px); }
.btn:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }

.status {
  margin-top: 10px;
  color: var(--muted);
  font-size: 14px;
  display: flex;
  align-items: center;
  gap: 6px;
  flex-wrap: wrap;
}
.status strong { color: var(--text); }
.sep { margin: 0 6px; opacity: 0.6; }

.game { margin-top: 14px; display: grid; place-items: center; }

.grid {
  display: grid;
  grid-template-columns: repeat(9, minmax(0, 1fr));
  gap: 0;
  width: min(92vw, 540px);
  aspect-ratio: 1 / 1;
  border: 2px solid var(--border);
  border-radius: 14px;
  overflow: hidden;
  background: rgba(0,0,0,0.12);
  box-shadow: var(--shadow);
  animation: fadeIn 0.5s ease-out;
}

.cell {
  width: 100%;
  height: 100%;
  display: grid;
  place-items: center;
  border-right: 1px solid var(--border);
  border-bottom: 1px solid var(--border);
  background: var(--cell);
  transition: background 0.2s ease;
}

.cell:nth-child(9n) { border-right: none; }
.cell:nth-last-child(-n + 9) { border-bottom: none; }

.cell.thick-right { border-right: 2px solid rgba(232,238,252,0.28); }
.cell.thick-bottom { border-bottom: 2px solid rgba(232,238,252,0.28); }

[data-theme="light"] .cell.thick-right,
[data-theme="light"] .cell.thick-bottom { border-color: rgba(15,23,42,0.22); }

.input {
  width: 100%;
  height: 100%;
  text-align: center;
  font-size: clamp(16px, 3.5vw, 22px);
  font-weight: 700;
  border: none;
  outline: none;
  background: transparent;
  color: var(--text);
  font-family: var(--font-display);
  caret-color: var(--accent);
  transition: transform 0.15s ease, background 0.2s ease;
}

.input.given { color: var(--accent); background: rgba(56, 189, 248, 0.12); }
.input.error { color: var(--danger); }
.input.conflict { background: rgba(251,113,133,0.10); }
.input.peer { background: rgba(56, 189, 248, 0.12); }
.input:focus-visible { transform: scale(1.03); }

.theme-toggle {
  position: fixed;
  right: 14px;
  bottom: 14px;
  width: 46px;
  height: 46px;
  border-radius: 999px;
  border: 1px solid var(--border);
  background: var(--panel);
  color: var(--text);
  cursor: pointer;
  box-shadow: var(--shadow);
}

@media (max-width: 420px) {
  .button-row { gap: 8px; }
  .btn { width: 100%; }
}

@keyframes fadeUp {
  from { opacity: 0; transform: translateY(8px); }
  to { opacity: 1; transform: translateY(0); }
}

@keyframes fadeIn {
  from { opacity: 0; transform: scale(0.98); }
  to { opacity: 1; transform: scale(1); }
}

@media (prefers-reduced-motion: reduce) {
  .container, .grid, .btn, .input { animation: none; transition: none; }
}