/* ===== CSS Variables & Reset ===== */
:root {
  --color-primary: #6366f1;
  --color-primary-dark: #4f46e5;
  --color-bg: #f8fafc;
  --color-surface: #ffffff;
  --color-surface-hover: #f1f5f9;
  --color-text: #1e293b;
  --color-text-secondary: #64748b;
  --color-border: #e2e8f0;
  --color-shadow: rgba(0, 0, 0, 0.08);
  --color-accent-green: #22c55e;
  --color-accent-orange: #f97316;
  --color-accent-blue: #3b82f6;
  --color-accent-purple: #a855f7;
  --color-accent-red: #ef4444;
  --color-accent-yellow: #eab308;
  --radius-sm: 6px;
  --radius-md: 10px;
  --radius-lg: 16px;
  --shadow-sm: 0 1px 3px var(--color-shadow);
  --shadow-md: 0 4px 12px var(--color-shadow);
  --shadow-lg: 0 8px 30px var(--color-shadow);
  --transition-fast: 0.2s ease;
  --transition-normal: 0.3s ease;
  --font-sans: 'Segoe UI', 'Microsoft JhengHei', system-ui, sans-serif;
  --header-height: 64px;
}

[data-theme="dark"] {
  --color-bg: #0f172a;
  --color-surface: #1e293b;
  --color-surface-hover: #334155;
  --color-text: #f1f5f9;
  --color-text-secondary: #94a3b8;
  --color-border: #334155;
  --color-shadow: rgba(0, 0, 0, 0.3);
}

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

html {
  scroll-behavior: smooth;
}

body {
  font-family: var(--font-sans);
  background: var(--color-bg);
  color: var(--color-text);
  line-height: 1.6;
  min-height: 100vh;
  transition: background var(--transition-normal), color var(--transition-normal);
}

a {
  color: inherit;
  text-decoration: none;
}

img {
  max-width: 100%;
  display: block;
}

button {
  font-family: inherit;
  cursor: pointer;
  border: none;
  background: none;
  color: inherit;
}

.container {
  max-width: 1200px;
  margin: 0 auto;
  padding: 0 1.5rem;
}

/* ===== Header ===== */
.header {
  position: sticky;
  top: 0;
  z-index: 100;
  background: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
  height: var(--header-height);
  transition: background var(--transition-normal), border-color var(--transition-normal);
}

.header-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 100%;
}

.logo {
  display: flex;
  align-items: center;
  gap: 0.6rem;
  font-weight: 700;
  font-size: 1.25rem;
  color: var(--color-primary);
}

.logo svg {
  flex-shrink: 0;
}

.nav {
  display: flex;
  align-items: center;
  gap: 1rem;
}

/* ===== Theme Toggle ===== */
.theme-toggle {
  display: flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: var(--radius-md);
  color: var(--color-text-secondary);
  transition: background var(--transition-fast), color var(--transition-fast);
}

.theme-toggle:hover {
  background: var(--color-surface-hover);
  color: var(--color-primary);
}

.icon-sun { display: none; }
.icon-moon { display: block; }

[data-theme="dark"] .icon-sun { display: block; }
[data-theme="dark"] .icon-moon { display: none; }

/* ===== Hero ===== */
.hero {
  padding: 4rem 0 3rem;
  text-align: center;
}

.hero h1 {
  font-size: clamp(2rem, 5vw, 3rem);
  font-weight: 800;
  margin-bottom: 0.75rem;
  background: linear-gradient(135deg, var(--color-primary), var(--color-accent-purple));
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  background-clip: text;
}

.hero p {
  font-size: 1.125rem;
  color: var(--color-text-secondary);
  margin-bottom: 2rem;
}

/* ===== Search Box ===== */
.search-box {
  position: relative;
  max-width: 480px;
  margin: 0 auto;
}

.search-box svg {
  position: absolute;
  left: 1rem;
  top: 50%;
  transform: translateY(-50%);
  color: var(--color-text-secondary);
  pointer-events: none;
}

.search-box input {
  width: 100%;
  padding: 0.875rem 1rem 0.875rem 3rem;
  font-size: 1rem;
  border: 2px solid var(--color-border);
  border-radius: var(--radius-lg);
  background: var(--color-surface);
  color: var(--color-text);
  outline: none;
  transition: border-color var(--transition-fast), box-shadow var(--transition-fast);
}

.search-box input::placeholder {
  color: var(--color-text-secondary);
}

.search-box input:focus {
  border-color: var(--color-primary);
  box-shadow: 0 0 0 3px rgba(99, 102, 241, 0.15);
}

/* ===== Categories ===== */
.categories {
  padding: 0 0 2rem;
}

.category-list {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  justify-content: center;
}

.category-btn {
  padding: 0.5rem 1.25rem;
  border-radius: 50px;
  font-size: 0.875rem;
  font-weight: 600;
  border: 2px solid var(--color-border);
  color: var(--color-text-secondary);
  transition: all var(--transition-fast);
}

.category-btn:hover {
  border-color: var(--color-primary);
  color: var(--color-primary);
}

.category-btn.active {
  background: var(--color-primary);
  border-color: var(--color-primary);
  color: white;
}

/* ===== Games Grid ===== */
.games-section {
  padding: 0 0 4rem;
}

.games-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(260px, 1fr));
  gap: 1.5rem;
}

.game-card {
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-lg);
  overflow: hidden;
  transition: transform var(--transition-fast), box-shadow var(--transition-fast), background var(--transition-normal), border-color var(--transition-normal);
  cursor: pointer;
  display: flex;
  flex-direction: column;
}

.game-card:hover {
  transform: translateY(-4px);
  box-shadow: var(--shadow-lg);
}

.game-card-thumb {
  height: 160px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 3.5rem;
  position: relative;
  overflow: hidden;
}

.game-card-thumb::after {
  content: '';
  position: absolute;
  inset: 0;
  background: linear-gradient(to bottom, transparent 60%, rgba(0,0,0,0.05));
}

.game-card-body {
  padding: 1.25rem;
  flex: 1;
  display: flex;
  flex-direction: column;
  gap: 0.5rem;
}

.game-card-title {
  font-size: 1.125rem;
  font-weight: 700;
}

.game-card-desc {
  font-size: 0.875rem;
  color: var(--color-text-secondary);
  flex: 1;
}

.game-card-tags {
  display: flex;
  flex-wrap: wrap;
  gap: 0.375rem;
  margin-top: 0.5rem;
}

.tag {
  display: inline-block;
  padding: 0.2rem 0.6rem;
  border-radius: 50px;
  font-size: 0.75rem;
  font-weight: 600;
  background: var(--color-bg);
  color: var(--color-text-secondary);
  border: 1px solid var(--color-border);
}

.game-card-play {
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 0.5rem;
  margin-top: 0.75rem;
  padding: 0.6rem;
  border-radius: var(--radius-md);
  background: var(--color-primary);
  color: white;
  font-weight: 600;
  font-size: 0.875rem;
  transition: background var(--transition-fast);
}

.game-card-play:hover {
  background: var(--color-primary-dark);
}

/* ===== Empty State ===== */
.empty-state {
  text-align: center;
  padding: 4rem 1rem;
  color: var(--color-text-secondary);
  font-size: 1.125rem;
}

/* ===== Footer ===== */
.footer {
  border-top: 1px solid var(--color-border);
  padding: 2rem 0;
  text-align: center;
  color: var(--color-text-secondary);
  font-size: 0.875rem;
  transition: border-color var(--transition-normal);
}

/* ===== Game Page ===== */
.game-page {
  min-height: calc(100vh - var(--header-height) - 80px);
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 2rem 1rem;
}

.game-page-header {
  display: flex;
  align-items: center;
  gap: 1rem;
  margin-bottom: 1.5rem;
  width: 100%;
  max-width: 640px;
}

.game-page-header a {
  display: flex;
  align-items: center;
  gap: 0.375rem;
  color: var(--color-text-secondary);
  font-size: 0.875rem;
  font-weight: 600;
  padding: 0.5rem 0.75rem;
  border-radius: var(--radius-md);
  border: 1px solid var(--color-border);
  transition: all var(--transition-fast);
}

.game-page-header a:hover {
  color: var(--color-primary);
  border-color: var(--color-primary);
}

.game-page-title {
  font-size: 1.5rem;
  font-weight: 800;
  flex: 1;
  text-align: center;
}

.game-score {
  font-size: 1.125rem;
  font-weight: 700;
  color: var(--color-primary);
  padding: 0.5rem 1rem;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
}

.game-canvas-wrapper {
  position: relative;
  border-radius: var(--radius-lg);
  overflow: hidden;
  box-shadow: var(--shadow-lg);
  border: 2px solid var(--color-border);
}

.game-canvas-wrapper canvas {
  display: block;
}

.game-instructions {
  margin-top: 1.5rem;
  padding: 1rem 1.5rem;
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-md);
  max-width: 640px;
  width: 100%;
  font-size: 0.875rem;
  color: var(--color-text-secondary);
  text-align: center;
  line-height: 1.8;
}

.game-instructions kbd {
  display: inline-block;
  padding: 0.15rem 0.5rem;
  background: var(--color-bg);
  border: 1px solid var(--color-border);
  border-radius: var(--radius-sm);
  font-family: monospace;
  font-size: 0.8rem;
  color: var(--color-text);
}

/* ===== 2048 Specific ===== */
.game-2048-grid {
  display: grid;
  grid-template-columns: repeat(4, 1fr);
  gap: 8px;
  padding: 12px;
  background: #bbada0;
  border-radius: var(--radius-md);
}

[data-theme="dark"] .game-2048-grid {
  background: #6b5b4e;
}

.tile-2048 {
  width: 80px;
  height: 80px;
  display: flex;
  align-items: center;
  justify-content: center;
  font-size: 1.5rem;
  font-weight: 800;
  border-radius: var(--radius-sm);
  background: #cdc1b4;
  color: #776e65;
  transition: all 0.1s ease;
}

.tile-2048[data-value="2"]    { background: #eee4da; color: #776e65; }
.tile-2048[data-value="4"]    { background: #ede0c8; color: #776e65; }
.tile-2048[data-value="8"]    { background: #f2b179; color: #f9f6f2; }
.tile-2048[data-value="16"]   { background: #f59563; color: #f9f6f2; }
.tile-2048[data-value="32"]   { background: #f67c5f; color: #f9f6f2; }
.tile-2048[data-value="64"]   { background: #f65e3b; color: #f9f6f2; }
.tile-2048[data-value="128"]  { background: #edcf72; color: #f9f6f2; font-size: 1.3rem; }
.tile-2048[data-value="256"]  { background: #edcc61; color: #f9f6f2; font-size: 1.3rem; }
.tile-2048[data-value="512"]  { background: #edc850; color: #f9f6f2; font-size: 1.3rem; }
.tile-2048[data-value="1024"] { background: #edc53f; color: #f9f6f2; font-size: 1.1rem; }
.tile-2048[data-value="2048"] { background: #edc22e; color: #f9f6f2; font-size: 1.1rem; }

.tile-2048.new {
  animation: tileAppear 0.2s ease;
}

.tile-2048.merged {
  animation: tileMerge 0.2s ease;
}

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

@keyframes tileMerge {
  0%   { transform: scale(1); }
  50%  { transform: scale(1.2); }
  100% { transform: scale(1); }
}

.game-2048-overlay {
  position: absolute;
  inset: 0;
  background: rgba(238, 228, 218, 0.73);
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  border-radius: var(--radius-lg);
  gap: 1rem;
}

[data-theme="dark"] .game-2048-overlay {
  background: rgba(30, 41, 59, 0.85);
}

.game-2048-overlay h2 {
  font-size: 2rem;
  font-weight: 800;
  color: #776e65;
}

[data-theme="dark"] .game-2048-overlay h2 {
  color: #f1f5f9;
}

.game-2048-overlay button {
  padding: 0.75rem 2rem;
  background: #8f7a66;
  color: white;
  border-radius: var(--radius-md);
  font-size: 1rem;
  font-weight: 700;
  transition: background var(--transition-fast);
}

.game-2048-overlay button:hover {
  background: #7f6a56;
}

/* ===== Responsive ===== */
@media (max-width: 768px) {
  .hero {
    padding: 2.5rem 0 2rem;
  }

  .hero h1 {
    font-size: 1.75rem;
  }

  .hero p {
    font-size: 1rem;
  }

  .games-grid {
    grid-template-columns: repeat(auto-fill, minmax(160px, 1fr));
    gap: 1rem;
  }

  .game-card-thumb {
    height: 110px;
    font-size: 2.5rem;
  }

  .game-card-body {
    padding: 0.875rem;
  }

  .game-card-title {
    font-size: 0.95rem;
  }

  .game-card-desc {
    font-size: 0.8rem;
    display: -webkit-box;
    -webkit-line-clamp: 2;
    -webkit-box-orient: vertical;
    overflow: hidden;
  }

  .tile-2048 {
    width: 64px;
    height: 64px;
    font-size: 1.2rem;
  }

  .tile-2048[data-value="128"],
  .tile-2048[data-value="256"],
  .tile-2048[data-value="512"] {
    font-size: 1rem;
  }

  .tile-2048[data-value="1024"],
  .tile-2048[data-value="2048"] {
    font-size: 0.85rem;
  }
}

@media (max-width: 480px) {
  .games-grid {
    grid-template-columns: repeat(2, 1fr);
    gap: 0.75rem;
  }

  .game-card-body {
    padding: 0.75rem;
  }

  .game-card-play {
    font-size: 0.75rem;
    padding: 0.5rem;
  }

  .tile-2048 {
    width: 56px;
    height: 56px;
    font-size: 1rem;
  }
}

@media (min-width: 769px) and (max-width: 1024px) {
  .games-grid {
    grid-template-columns: repeat(3, 1fr);
  }
}