/* Main stylesheet for Game-Playing AI website */

:root {
  --primary-color: #2563eb;
  --secondary-color: #64748b;
  --background-color: #ffffff;
  --text-color: #1e293b;
  --border-color: #e2e8f0;
  --spacing-unit: 1rem;
  --spacing-xs: 0.5rem;   /* spacing-unit * 0.5 */
  --spacing-sm: 0.75rem;  /* spacing-unit * 0.75 */
  --spacing-lg: 2rem;     /* spacing-unit * 2 */
  --spacing-xl: 3rem;     /* spacing-unit * 3 */
  --spacing-2xl: 4rem;    /* spacing-unit * 4 */
  --spacing-3xl: 8rem;    /* spacing-unit * 8 */
  --success-color: #10b981;
  --warning-color: #f59e0b;
  --danger-color: #ef4444;
}

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

html, body {
  font-family: -apple-system, BlinkMacSystemFont, 'Segoe UI', Roboto, Oxygen, Ubuntu, Cantarell, sans-serif;
  background-color: var(--background-color);
  color: var(--text-color);
  line-height: 1.6;
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 var(--spacing-unit);
}

/* Header & Navigation */
.site-header {
  background-color: #f8fafc;
  border-bottom: 1px solid var(--border-color);
  position: sticky;
  top: 0;
  z-index: 100;
}

.navbar {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: var(--spacing-unit) 0;
}

.navbar-brand {
  flex: 0 0 auto;
}

.site-title {
  font-size: 1.5rem;
  font-weight: bold;
  color: var(--primary-color);
  text-decoration: none;
}

.site-title:hover {
  color: #1d4ed8;
}

.navbar-menu {
  display: flex;
  list-style: none;
  gap: var(--spacing-lg);
}

.navbar-menu a {
  color: var(--secondary-color);
  text-decoration: none;
  padding: var(--spacing-unit) 0;
  border-bottom: 2px solid transparent;
  transition: all 0.3s ease;
}

.navbar-menu a:hover,
.navbar-menu a.active {
  color: var(--primary-color);
  border-bottom-color: var(--primary-color);
}

/* Main Content */
.main-content {
  min-height: calc(100vh - 200px);
  padding: var(--spacing-xl) 0;
}

/* Breadcrumb */
.breadcrumb {
  font-size: 0.9rem;
  color: var(--secondary-color);
  margin-bottom: var(--spacing-lg);
  padding-bottom: var(--spacing-unit);
  border-bottom: 1px solid var(--border-color);
}

.breadcrumb a {
  color: var(--primary-color);
  text-decoration: none;
}

.breadcrumb a:hover {
  text-decoration: underline;
}

/* Hero Section */
.hero {
  background: linear-gradient(135deg, #667eea 0%, #764ba2 100%);
  color: white;
  padding: var(--spacing-3xl) var(--spacing-unit);
  text-align: center;
  border-radius: 0.5rem;
  margin-bottom: var(--spacing-2xl);
}

.hero-content h1 {
  font-size: 3rem;
  margin-bottom: var(--spacing-unit);
  font-weight: bold;
}

.hero .subtitle {
  font-size: 1.5rem;
  margin-bottom: var(--spacing-lg);
  opacity: 0.95;
}

.hero .description {
  font-size: 1.1rem;
  max-width: 600px;
  margin: 0 auto var(--spacing-xl);
  opacity: 0.9;
  line-height: 1.8;
}

.cta-buttons {
  display: flex;
  gap: var(--spacing-unit);
  justify-content: center;
  flex-wrap: wrap;
}

/* Buttons */
.btn {
  padding: var(--spacing-sm) var(--spacing-lg);
  border-radius: 0.375rem;
  text-decoration: none;
  font-weight: 600;
  transition: all 0.3s ease;
  display: inline-block;
  border: none;
  cursor: pointer;
  font-size: 1rem;
}

.btn-primary {
  background-color: white;
  color: #667eea;
}

.btn-primary:hover {
  background-color: #f1f5f9;
  transform: translateY(-2px);
}

.btn-secondary {
  background-color: transparent;
  color: var(--primary-color);
  border: 2px solid var(--primary-color);
}

.btn-secondary:hover {
  background-color: var(--primary-color);
  color: white;
  transform: translateY(-2px);
}

/* Games Grid */
.games-grid {
  margin-bottom: var(--spacing-2xl);
}

.games-grid h2 {
  font-size: 2rem;
  margin-bottom: var(--spacing-xl);
  text-align: center;
}

.game-cards {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: var(--spacing-lg);
}

.game-card {
  background: white;
  border: 1px solid var(--border-color);
  border-radius: 0.5rem;
  padding: var(--spacing-lg);
  transition: all 0.3s ease;
}

.game-card:hover {
  box-shadow: 0 10px 25px rgba(0, 0, 0, 0.1);
  border-color: var(--primary-color);
}

.game-card h3 {
  color: var(--primary-color);
  margin-bottom: var(--spacing-unit);
  font-size: 1.25rem;
}

.game-card ul {
  list-style: none;
}

.game-card li {
  padding: var(--spacing-xs) 0;
  border-bottom: 1px solid var(--border-color);
}

.game-card li:last-child {
  border-bottom: none;
}

.game-card a {
  color: var(--primary-color);
  text-decoration: none;
  transition: color 0.3s ease;
}

.game-card a:hover {
  color: #1d4ed8;
  text-decoration: underline;
}

/* Game Article */
.game-article {
  max-width: 900px;
  margin: 0 auto;
}

.game-article h1 {
  font-size: 2.5rem;
  margin-bottom: var(--spacing-unit);
}

.meta {
  display: flex;
  gap: var(--spacing-unit);
  margin-bottom: var(--spacing-lg);
  align-items: center;
  flex-wrap: wrap;
}

.difficulty {
  display: inline-block;
  padding: var(--spacing-xs) var(--spacing-unit);
  border-radius: 9999px;
  font-size: 0.85rem;
  font-weight: 600;
}

.difficulty-easy {
  background-color: #dcfce7;
  color: #166534;
}

.difficulty-medium {
  background-color: #fef3c7;
  color: #92400e;
}

.difficulty-hard {
  background-color: #fee2e2;
  color: #991b1b;
}

.algorithms {
  color: var(--secondary-color);
  font-size: 0.95rem;
}

.game-content {
  margin: var(--spacing-xl) 0;
  line-height: 1.8;
}

.game-content h2 {
  font-size: 1.75rem;
  margin-top: var(--spacing-lg);
  margin-bottom: var(--spacing-unit);
  border-bottom: 2px solid var(--border-color);
  padding-bottom: var(--spacing-unit) * 0.5;
}

.game-content h3 {
  font-size: 1.25rem;
  margin-top: calc(var(--spacing-unit) * 1.5);
  margin-bottom: var(--spacing-unit) * 0.5;
}

.game-content p {
  margin-bottom: var(--spacing-unit);
}

.game-content ul, .game-content ol {
  margin-left: var(--spacing-lg);
  margin-bottom: var(--spacing-unit);
}

.game-content li {
  margin-bottom: var(--spacing-xs);
}

.game-content code {
  background-color: #f1f5f9;
  padding: 0.2em 0.4em;
  border-radius: 0.3em;
  font-family: 'Courier New', monospace;
  font-size: 0.9em;
}

.game-content pre {
  background-color: #1e293b;
  color: #e2e8f0;
  padding: var(--spacing-unit);
  border-radius: 0.5rem;
  overflow-x: auto;
  margin: var(--spacing-unit) 0;
}

.game-content pre code {
  background-color: transparent;
  padding: 0;
  color: inherit;
}

/* Game Navigation */
.game-nav {
  display: flex;
  justify-content: space-between;
  gap: var(--spacing-unit);
  margin-top: var(--spacing-2xl);
  padding-top: var(--spacing-unit) * 2;
  border-top: 1px solid var(--border-color);
  flex-wrap: wrap;
}

/* About Section */
.about {
  background-color: #f8fafc;
  padding: var(--spacing-xl);
  border-radius: 0.5rem;
  margin-bottom: var(--spacing-2xl);
}

.about h2 {
  font-size: 2rem;
  margin-bottom: var(--spacing-lg);
}

.about p {
  margin-bottom: var(--spacing-unit);
  line-height: 1.8;
}

.about ul {
  margin-left: var(--spacing-lg);
  margin-bottom: var(--spacing-lg);
}

.about li {
  margin-bottom: var(--spacing-sm);
}

/* Algorithm Preview */
.algorithms-preview h2 {
  font-size: 2rem;
  margin-bottom: var(--spacing-xl);
}

.algorithm-list {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(250px, 1fr));
  gap: var(--spacing-lg);
  margin-bottom: var(--spacing-xl);
}

.algo-item {
  background: white;
  border-left: 4px solid var(--primary-color);
  padding: calc(var(--spacing-unit) * 1.5);
  border-radius: 0.375rem;
  border: 1px solid var(--border-color);
}

.algo-item h4 {
  color: var(--primary-color);
  margin-bottom: var(--spacing-unit) * 0.5;
}

.algo-item p {
  color: var(--secondary-color);
  font-size: 0.95rem;
}

/* Links */
.link-primary {
  color: var(--primary-color);
  text-decoration: none;
  font-weight: 600;
  transition: color 0.3s ease;
}

.link-primary:hover {
  color: #1d4ed8;
  text-decoration: underline;
}

/* Footer */
.site-footer {
  background-color: #1e293b;
  color: #cbd5e1;
  text-align: center;
  padding: var(--spacing-xl) var(--spacing-unit);
  margin-top: var(--spacing-2xl);
}

.site-footer a {
  color: var(--primary-color);
  text-decoration: none;
}

.site-footer a:hover {
  text-decoration: underline;
}

/* Demo/Interactive Elements */
.demo-container {
  background-color: #f8fafc;
  border: 1px solid var(--border-color);
  border-radius: 0.5rem;
  padding: var(--spacing-lg);
  margin: var(--spacing-lg) 0;
}

.demo-title {
  font-weight: 600;
  margin-bottom: var(--spacing-unit);
  color: var(--primary-color);
}

/* Responsive */
@media (max-width: 768px) {
  .hero-content h1 {
    font-size: 2rem;
  }

  .hero .subtitle {
    font-size: 1.2rem;
  }

  .cta-buttons {
    flex-direction: column;
  }

  .btn {
    width: 100%;
    text-align: center;
  }

  .navbar {
    flex-direction: column;
    gap: var(--spacing-unit);
  }

  .navbar-menu {
    flex-direction: column;
    gap: var(--spacing-unit);
    text-align: center;
    width: 100%;
  }

  .game-nav {
    flex-direction: column;
  }

  .game-nav .btn {
    width: 100%;
  }

  .game-article h1 {
    font-size: 1.75rem;
  }
}