*,
*::before,
*::after {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

:root {
  --bg: #faf8f2;
  --bg-2: #f4f0e8;
  --surface: #ffffff;
  --border: #e8ddd0;
  --fg: #1a1a1a;
  --fg-muted: #6b6b6b;
  --accent: #d4a847;
  --accent-light: #e8c975;
  --accent-dark: #c2940c;
  
  --transition: 280ms cubic-bezier(0.25, 0.1, 0.25, 1);
  --spacing-xs: 8px;
  --spacing-sm: 16px;
  --spacing-md: 24px;
  --spacing-lg: 32px;
  --spacing-xl: 40px;
  --spacing-2xl: 64px;
}

@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0a0a0a;
    --bg-2: #141414;
    --surface: #1a1a1a;
    --border: #2a2a2a;
    --fg: #faf8f2;
    --fg-muted: #a8a8a8;
    --accent: #e8c975;
    --accent-light: #f0d891;
    --accent-dark: #d4a847;
  }
}

html {
  scroll-behavior: smooth;
}

body {
  font-family: 'Inter', -apple-system, BlinkMacSystemFont, 'Segoe UI', sans-serif;
  background-color: var(--bg);
  color: var(--fg);
  line-height: 1.6;
  letter-spacing: -0.01em;
  -webkit-font-smoothing: antialiased;
}

.container {
  min-height: 100vh;
  display: flex;
  flex-direction: column;
}

header.header {
  position: sticky;
  top: 0;
  z-index: 40;
  border-bottom: 1px solid var(--border);
  background-color: var(--bg);
  backdrop-filter: blur(8px);
  background-color: color-mix(in srgb, var(--bg) 95%, transparent);
}

.header-content {
  max-width: 1200px;
  margin: 0 auto;
  padding: var(--spacing-md) var(--spacing-lg);
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo {
  display: flex;
  align-items: center;
  gap: var(--spacing-sm);
  text-decoration: none;
  cursor: pointer;
  transition: transform var(--transition);
}

.logo:hover {
  transform: translateY(-1px);
}

.logo-icon {
  width: 32px;
  height: 32px;
  color: var(--accent);
}

.logo-text {
  font-family: 'JetBrains Mono', monospace;
  font-size: 18px;
  font-weight: 700;
  letter-spacing: 0.08em;
  color: var(--fg);
}

.nav-links {
  display: flex;
  gap: var(--spacing-lg);
  background: none;
  border: none;
}

.nav-item {
  background: none;
  border: none;
  cursor: pointer;
  font-size: 14px;
  font-weight: 500;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  color: var(--fg-muted);
  transition: color var(--transition);
  padding: 0;
}

.nav-item:hover {
  color: var(--accent);
}

.nav-item.active {
  color: var(--accent);
  border-bottom: 2px solid var(--accent);
  padding-bottom: 2px;
}

.main-content {
  flex: 1;
  max-width: 1200px;
  margin: 0 auto;
  width: 100%;
  padding: var(--spacing-xl) var(--spacing-lg);
}

.section-header {
  margin-bottom: var(--spacing-2xl);
  text-align: center;
  animation: fadeUp 600ms var(--transition) both;
}

@keyframes fadeUp {
  from {
    opacity: 0;
    transform: translateY(20px);
  }
  to {
    opacity: 1;
    transform: translateY(0);
  }
}

.title {
  font-family: 'JetBrains Mono', monospace;
  font-size: clamp(28px, 8vw, 56px);
  font-weight: 700;
  line-height: 1.1;
  margin-bottom: var(--spacing-md);
  letter-spacing: -0.02em;
}

.subtitle {
  font-size: 18px;
  color: var(--fg-muted);
  font-weight: 400;
  max-width: 600px;
  margin: 0 auto;
}

.game-wrapper {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-xl);
  animation: fadeUp 600ms var(--transition) 80ms both;
}

.game-info {
  display: flex;
  justify-content: space-between;
  align-items: flex-end;
  gap: var(--spacing-lg);
  padding-bottom: var(--spacing-lg);
  border-bottom: 2px solid var(--border);
}

.player-info,
.ai-info {
  flex: 1;
  text-align: center;
}

.player-label {
  font-size: 14px;
  font-weight: 500;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--fg-muted);
  margin-bottom: var(--spacing-sm);
}

.score {
  font-family: 'JetBrains Mono', monospace;
  font-size: 48px;
  font-weight: 700;
  color: var(--accent);
  line-height: 1;
}

.vs-separator {
  display: flex;
  align-items: center;
  height: 100%;
  padding-bottom: 12px;
}

.vs-text {
  font-size: 12px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--fg-muted);
  font-weight: 600;
}

.board-container {
  display: flex;
  justify-content: center;
  padding: var(--spacing-lg) 0;
}

.board {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 8px;
  aspect-ratio: 1;
  width: 100%;
  max-width: 480px;
  padding: var(--spacing-md);
  background: linear-gradient(135deg, var(--bg-2), var(--surface));
  border: 1px solid var(--border);
}

.square {
  aspect-ratio: 1;
  border: 2px solid var(--border);
  background-color: var(--surface);
  cursor: pointer;
  font-family: 'JetBrains Mono', monospace;
  font-size: 32px;
  font-weight: 700;
  color: var(--fg);
  transition: all var(--transition);
  position: relative;
  overflow: hidden;
}

.square::before {
  content: '';
  position: absolute;
  inset: 0;
  background: var(--accent);
  opacity: 0;
  z-index: -1;
  transition: opacity var(--transition);
}

.square:hover:not(:disabled) {
  border-color: var(--accent);
  transform: translateY(-2px);
}

.square:hover:not(:disabled)::before {
  opacity: 0.05;
}

.square:disabled {
  cursor: not-allowed;
  background-color: var(--bg-2);
}

.game-controls {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
  align-items: center;
  padding-top: var(--spacing-lg);
  animation: fadeUp 600ms var(--transition) 160ms both;
}

.status-message {
  font-family: 'JetBrains Mono', monospace;
  font-size: 16px;
  font-weight: 500;
  color: var(--accent);
  min-height: 24px;
  letter-spacing: 0.05em;
}

.button {
  padding: var(--spacing-md) var(--spacing-lg);
  border: none;
  cursor: pointer;
  font-size: 14px;
  font-weight: 600;
  letter-spacing: 0.05em;
  text-transform: uppercase;
  transition: all var(--transition);
  font-family: 'Inter', sans-serif;
}

.button-primary {
  background-color: var(--accent);
  color: var(--bg);
  min-width: 200px;
}

.button-primary:hover {
  background-color: var(--accent-light);
  transform: translateY(-2px);
  box-shadow: 0 8px 24px rgba(212, 168, 71, 0.15);
}

.button-secondary {
  background-color: transparent;
  color: var(--fg);
  border: 1px solid var(--border);
  min-width: 200px;
}

.button-secondary:hover {
  border-color: var(--fg);
  background-color: var(--bg-2);
}

.leaderboard-section {
  animation: fadeUp 600ms var(--transition) both;
}

.leaderboard-container {
  margin-top: var(--spacing-2xl);
}

.leaderboard-list {
  display: flex;
  flex-direction: column;
  gap: var(--spacing-md);
}

.leaderboard-item {
  display: flex;
  align-items: center;
  justify-content: space-between;
  padding: var(--spacing-md) var(--spacing-lg);
  background-color: var(--surface);
  border: 1px solid var(--border);
  border-radius: 0;
  transition: all var(--transition);
  animation: slideIn 400ms var(--transition) both;
}

@keyframes slideIn {
  from {
    opacity: 0;
    transform: translateX(-20px);
  }
  to {
    opacity: 1;
    transform: translateX(0);
  }
}

.leaderboard-item:hover {
  border-color: var(--accent);
  background-color: var(--bg-2);
  transform: translateX(4px);
}

.leaderboard-rank {
  font-family: 'JetBrains Mono', monospace;
  font-size: 14px;
  font-weight: 700;
  color: var(--accent);
  min-width: 32px;
}

.leaderboard-info {
  flex: 1;
  margin: 0 var(--spacing-lg);
}

.leaderboard-name {
  font-size: 16px;
  font-weight: 600;
  color: var(--fg);
  margin-bottom: 4px;
}

.leaderboard-score {
  font-family: 'JetBrains Mono', monospace;
  font-size: 24px;
  font-weight: 700;
  color: var(--fg);
}

.empty-state {
  text-align: center;
  padding: var(--spacing-2xl) var(--spacing-lg);
  color: var(--fg-muted);
  font-size: 16px;
}

.footer {
  margin-top: var(--spacing-2xl);
  padding: var(--spacing-lg);
  border-top: 1px solid var(--border);
  text-align: center;
  color: var(--fg-muted);
  font-size: 13px;
  letter-spacing: 0.04em;
}

.footer-divider {
  margin: 0 var(--spacing-sm);
}

.footer-detail {
  display: inline;
}

@media (max-width: 640px) {
  .header-content {
    padding: var(--spacing-md);
  }

  .nav-links {
    gap: var(--spacing-md);
  }

  .main-content {
    padding: var(--spacing-lg) var(--spacing-md);
  }

  .section-header {
    margin-bottom: var(--spacing-xl);
  }

  .title {
    font-size: clamp(24px, 6vw, 32px);
  }

  .game-info {
    gap: var(--spacing-md);
    padding-bottom: var(--spacing-md);
  }

  .score {
    font-size: 32px;
  }

  .board {
    max-width: 360px;
    gap: 6px;
    padding: var(--spacing-md);
  }

  .square {
    font-size: 24px;
  }

  .button {
    min-width: auto;
    width: 100%;
    max-width: 300px;
  }

  .leaderboard-item {
    flex-direction: column;
    gap: var(--spacing-md);
    align-items: flex-start;
  }

  .leaderboard-info {
    margin: 0;
    width: 100%;
  }
}

@media (max-width: 480px) {
  .game-info {
    flex-wrap: wrap;
  }

  .player-info,
  .ai-info {
    flex: 1 1 calc(50% - var(--spacing-sm)/2);
  }

  .vs-separator {
    flex: 0 0 100%;
    justify-content: center;
    height: auto;
    padding: var(--spacing-md) 0;
    padding-bottom: 0;
    border-top: 1px solid var(--border);
    margin-top: var(--spacing-md);
  }

  .title {
    font-size: 20px;
  }

  .subtitle {
    font-size: 14px;
  }

  .board {
    max-width: 100%;
  }
}