:root {
  color-scheme: dark;
  --bg: #050510;
  --surface: #111128;
  --primary: #7dd3fc;
  --accent: #f472b6;
  --grid: #1f1f3d;
  --grid-strong: #3c3c6d;
  --text: #f7fafc;
  --muted: #9ca3af;
}

* {
  box-sizing: border-box;
  font-family: 'Space Grotesk', system-ui, -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
}

body {
  margin: 0;
  min-height: 100vh;
  background: radial-gradient(circle at top, rgba(124,58,237,0.3), transparent 60%),
              radial-gradient(circle at 20% 20%, rgba(14,165,233,0.35), transparent 45%),
              var(--bg);
  color: var(--text);
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 32px 16px;
}

.app {
  width: min(960px, 100%);
  background: var(--surface);
  padding: 32px;
  border-radius: 24px;
  box-shadow: 0 25px 60px rgba(0,0,0,0.45);
}

header {
  text-align: center;
  margin-bottom: 24px;
}

header h1 {
  margin: 0 0 8px;
  font-size: clamp(2rem, 5vw, 3rem);
  color: var(--primary);
}

header p {
  margin: 0;
  color: var(--muted);
}

.hud {
  margin-top: 16px;
  display: flex;
  justify-content: center;
  gap: 32px;
  text-transform: uppercase;
  font-size: 0.85rem;
  letter-spacing: 0.1em;
}

.hud .label {
  display: block;
  color: var(--muted);
  font-size: 0.75rem;
  margin-bottom: 4px;
}

.hud strong {
  font-size: 1.2rem;
}

.board {
  display: grid;
  grid-template-columns: repeat(9, minmax(30px, 1fr));
  grid-template-rows: repeat(9, minmax(30px, 1fr));
  gap: 2px;
  background: var(--grid);
  padding: 6px;
  border-radius: 16px;
  border: 2px solid var(--grid-strong);
}

.cell {
  width: 100%;
  aspect-ratio: 1;
  background: var(--surface);
  border: 1px solid rgba(255,255,255,0.05);
  display: grid;
  place-items: center;
  font-size: clamp(1rem, 3vw, 1.35rem);
  font-weight: 600;
  color: var(--text);
}

.cell input {
  width: 100%;
  height: 100%;
  text-align: center;
  background: transparent;
  border: none;
  font-weight: inherit;
  font-size: inherit;
  color: inherit;
  caret-color: var(--accent);
}

.cell input:focus {
  outline: 2px solid var(--accent);
  outline-offset: -2px;
}

.cell.given {
  background: rgba(125, 211, 252, 0.08);
  color: var(--primary);
}

.cell.invalid input {
  color: #f87171;
}

.controls {
  margin-top: 24px;
  display: flex;
  flex-direction: column;
  gap: 16px;
  align-items: center;
}

.buttons {
  display: flex;
  flex-wrap: wrap;
  gap: 12px;
  justify-content: center;
}

button {
  border: none;
  border-radius: 999px;
  padding: 12px 24px;
  font-size: 1rem;
  font-weight: 600;
  cursor: pointer;
  background: linear-gradient(120deg, var(--primary), var(--accent));
  color: #050510;
  transition: transform 0.15s ease, box-shadow 0.15s ease;
  box-shadow: 0 10px 25px rgba(15,118,110,0.35);
}

button:hover {
  transform: translateY(-2px);
  box-shadow: 0 15px 30px rgba(15,118,110,0.45);
}

button:active {
  transform: translateY(0);
}

#status {
  min-height: 1.4em;
  color: var(--muted);
  font-size: 0.95rem;
}

.score-panel {
  margin-top: 32px;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(260px, 1fr));
  gap: 16px;
}

.score-card {
  background: rgba(255,255,255,0.03);
  border: 1px solid rgba(255,255,255,0.06);
  border-radius: 20px;
  padding: 20px;
  display: flex;
  flex-direction: column;
  gap: 12px;
}

.score-card label {
  font-size: 0.9rem;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  color: var(--muted);
}

.score-card input {
  border-radius: 12px;
  border: 1px solid rgba(255,255,255,0.08);
  background: rgba(0,0,0,0.2);
  padding: 12px 14px;
  color: var(--text);
  font-size: 1rem;
}

.score-card small {
  color: var(--muted);
  font-size: 0.8rem;
}

.score-card button {
  width: fit-content;
}

.score-card .ghost {
  background: transparent;
  color: var(--primary);
  border: 1px solid rgba(125,211,252,0.5);
  box-shadow: none;
  padding: 6px 12px;
  font-size: 0.8rem;
  line-height: 1;
}

.scoreboard-header {
  display: flex;
  align-items: center;
  gap: 8px;
}

.scoreboard-header h2 {
  margin: 0;
  font-size: 1.2rem;
}

.scoreboard select {
  border-radius: 999px;
  padding: 6px 14px;
  background: rgba(0,0,0,0.3);
  color: var(--text);
  border: 1px solid rgba(255,255,255,0.08);
}

.leaderboard-list {
  list-style: decimal;
  margin: 0;
  padding-left: 20px;
  display: flex;
  flex-direction: column;
  gap: 6px;
}

.leaderboard-list li {
  display: flex;
  justify-content: space-between;
  font-size: 0.95rem;
}

.leaderboard-list span {
  color: var(--muted);
}

@media (max-width: 640px) {
  .app {
    padding: 20px;
  }
  .buttons button {
    flex: 1 1 calc(50% - 12px);
  }
  .hud {
    flex-direction: column;
    gap: 12px;
  }
}