body {
  margin: 0;
  padding: 0;
  font-family: 'Segoe UI', Tahoma, Geneva, Verdana, sans-serif;
  background-color: var(--bg-color);
  color: var(--text-color);
  display: flex;
  flex-direction: column;
  min-height: 100vh;
  box-sizing: border-box;
}

main {
  flex-grow: 1;
  display: flex;
  flex-direction: column;
  align-items: center;
  padding: 30px 20px 40px;
  /* メインコンテンツの上部にヘッダー分（またはそれ以上）の余白を確保 */
  padding-top: 150px;
}

.container {
  display: flex;
  gap: 25px;
  max-width: 1100px;
  width: 100%;
  flex-wrap: wrap;
  justify-content: center;
  margin-top: 20px;
}

.game-card {
  background-color: var(--card-bg);
  border-radius: 16px;
  width: 320px;
  padding: 30px;
  box-shadow: 0 10px 25px -5px rgba(0, 0, 0, 0.3);
  display: flex;
  flex-direction: column;
  justify-content: space-between;
  transition: transform 0.3s ease, box-shadow 0.3s ease;
  border: 1px solid var(--border-color);
  box-sizing: border-box;
}

.game-card:hover {
  transform: translateY(-8px);
  box-shadow: 0 20px 35px -10px rgba(0, 0, 0, 0.5);
  border-color: rgba(255, 255, 255, 0.25);
}

.game-icon {
  font-size: 3rem;
  margin-bottom: 15px;
}

.game-title {
  font-size: 1.5rem;
  font-weight: bold;
  margin: 0 0 10px 0;
  color: var(--text-color);
}

.game-desc {
  color: var(--text-muted);
  font-size: 0.95rem;
  line-height: 1.5;
  margin-bottom: 25px;
  flex-grow: 1;
}

.play-btn {
  display: inline-block;
  text-align: center;
  text-decoration: none;
  padding: 12px 0;
  border-radius: 8px;
  font-weight: bold;
  font-size: 1rem;
  color: white;
  transition: opacity 0.2s ease;
  width: 100%;
}

.play-btn.othello {
  background: linear-gradient(135deg, #059669, #10b981);
}

.play-btn.dino {
  background: linear-gradient(135deg, #2563eb, #3b82f6);
}

.play-btn.block {
  background: linear-gradient(135deg, #f59e0b, #ef4444);
}

.play-btn.drive {
  background: linear-gradient(135deg, #e0a3a3, #db0c0c);
}

.play-btn:hover {
  opacity: 0.9;
}

/* ページタイトルエリアのデザイン */
.page-header {
  text-align: center;
  margin-bottom: 30px;
}

.page-title {
  font-size: 2.5rem;
  font-weight: 800;
  margin: 0 0 10px 0;
  background: linear-gradient(135deg, #38bdf8, #818cf8);
  -webkit-background-clip: text;
  -webkit-text-fill-color: transparent;
  letter-spacing: 2px;
}

.subtitle {
  color: var(--text-muted, #94a3b8);
  font-size: 1.05rem;
  margin: 0;
}