@media (max-width: 768px) {
  .container {
    padding: 10px;
  }

  header h1 {
    font-size: 1.8em;
  }

  #category-nav {
    display: flex;
    flex-wrap: wrap;
    gap: 8px;
    padding-bottom: 10px;
  }

  #category-nav button {
    padding: 8px 16px;
    height: 36px;
    white-space: nowrap;
    overflow: hidden;
    text-overflow: ellipsis;
    max-width: calc(50% - 4px); /* 每行最多显示两个，减去间距 */
    flex: 1 0 auto;
  }

  #search-input {
    padding: 8px 12px;
    font-size: 14px;
  }

  #search-results {
    max-height: 250px;
  }

  .search-result-item {
    padding: 8px 12px;
    font-size: 14px;
  }

  .category-tag {
    font-size: 0.75em;
    padding: 1px 6px;
  }

  #question-card {
    padding: 20px;
  }

  .controls {
    padding: 10px;
  }

  .controls button {
    padding: 10px 20px;
    min-width: 120px;
  }
}

@media (max-width: 480px) {
  header h1 {
    font-size: 1.5em;
  }

  #category-nav button {
    font-size: 0.9em;
    min-width: calc(50% - 4px); /* 确保每行两个按钮 */
  }

  .controls {
    flex-direction: column;
    padding: 10px 15px;
  }

  .controls button {
    width: 100%;
    min-width: unset;
  }

  body {
    padding-bottom: 130px; /* 为双行按钮留出空间 */
  }
}