body {
  margin: 0;
  background-color: #111827;
  color: #ffffff;
  font-family: sans-serif;
  overflow: hidden;
}
.container { padding: 20px; }
.header {
  display: flex;
  justify-content: space-between;
  align-items: center;
  margin-bottom: 20px;
}
.grid {
  display: grid;
  grid-template-columns: repeat(3, 1fr);
  gap: 20px;
}
.card {
  background: #1f2937;
  border: 3px solid transparent;
  border-radius: 12px;
  padding: 20px;
  box-sizing: border-box;
  outline: none;
}
/* リモコンの十字キーで選択された時の黄色い枠線 */
.card:focus {
  border-color: #f59e0b;
  transform: scale(1.03);
  background: #374151;
}