* {
  box-sizing: border-box;
}

body {
  font-family: Arial, sans-serif;
  text-align: center;
  background-color: #f4f4f9;
  margin: 0;
  padding: 15px;
  touch-action: manipulation; /* スマホでのダブルタップ拡大防止 */
}

#info-panel {
  margin-bottom: 15px;
}

#best-time-container {
  display: flex;
  justify-content: center;
  align-items: center;
  gap: 10px;
  margin-bottom: 5px;
}

#best-time {
  font-size: 1rem;
  font-weight: bold;
  color: #e67e22;
}

#reset-btn {
  padding: 3px 8px;
  font-size: 0.8rem;
  color: #666;
  background-color: #e0e0e0;
  border: 1px solid #ccc;
  border-radius: 4px;
  cursor: pointer;
}

#target-num {
  font-size: 1.2rem;
  font-weight: bold;
  color: #333;
  min-height: 1.5em;
}

#timer {
  font-size: 2rem;
  font-weight: bold;
  color: #2c3e50;
}

/* 3×3 ゲーム盤面（レスポンシブ対応） */
#game-board {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  grid-template-rows: repeat(3, 1fr);
  gap: 2px;
  width: 100%;
  max-width: 360px; /* PCでの最大幅 */
  aspect-ratio: 1 / 1; /* 正方形を維持 */
  margin: 0 auto;
  border: 3px solid #333;
  background-color: #333;
  box-shadow: 0 4px 10px rgba(0,0,0,0.15);
}

/* 各セルボタン */
.cell-btn {
  width: 100%;
  height: 100%;
  border: none;
  font-size: 2rem;
  font-weight: bold;
  color: #000;
  cursor: pointer;
  display: flex;
  align-items: center;
  justify-content: center;
  user-select: none;
  -webkit-tap-highlight-color: transparent;
  transition: transform 0.05s;
}

.cell-btn:active {
  transform: scale(0.96);
}

/* スタートボタン */
#start-btn {
  margin-top: 20px;
  padding: 12px 32px;
  font-size: 1.2rem;
  font-weight: bold;
  color: white;
  background-color: #2ecc71;
  border: none;
  border-radius: 8px;
  cursor: pointer;
  box-shadow: 0 4px 6px rgba(0,0,0,0.1);
}

#start-btn:hover {
  background-color: #27ae60;
}

/* ミスタップ時のアニメーション */
.wrong {
  animation: shake 0.2s ease-in-out;
}

@keyframes shake {
  0% { transform: translateX(0); }
  25% { transform: translateX(-5px); }
  75% { transform: translateX(5px); }
  100% { transform: translateX(0); }
}