/* 강의 목록 */
.lecture-list {
    max-height: 500px;
    overflow-y: auto;
  }
  
  .lecture-item {
    display: flex;
    align-items: flex-start; /* center → flex-start로 변경 */
    padding: 16px;
    border-bottom: 1px solid #e5e7eb;
    cursor: pointer;
    transition: background 0.2s;
  }
  
  .lecture-item:hover {
    background: #f9fafb;
  }
  
  .lecture-item.active {
    background: #eff6ff;
    border-left: 4px solid var(--active-color);
  }
  
  .lecture-number {
    width: 32px;
    height: 32px;
    background: #e5e7eb;
    border-radius: 50%;
    display: flex;
    align-items: center;
    justify-content: center;
    font-weight: bold;
    font-size: 14px;
    color: #666;
    flex-shrink: 0;
    margin-right: 12px;
  }
  
  .lecture-item.active .lecture-number {
    background: var(--active-color);
    color: white;
  }
  
  .lecture-info {
    flex: 1;
    min-width: 0;
  }
  
  .lecture-title {
    font-weight: 600;
    font-size: 14px;
    color: #333;
    margin-bottom: 4px;
    overflow: hidden;
    display: -webkit-box;
    -webkit-line-clamp: 2; /* 최대 2줄 */
    -webkit-box-orient: vertical;
    line-height: 1.4;
    word-break: break-word;
  }
  
  .lecture-duration {
    font-size: 12px;
    color: #999;
  }
  
  /* 비디오 플레이어 영역 */
  .video-container {
    background: #000;
    aspect-ratio: 16 / 9;
    display: flex;
    align-items: center;
    justify-content: center;
  }
  
  .video-placeholder {
    text-align: center;
    color: white;
  }
  
  /* 스크롤바 스타일 */
  .lecture-list::-webkit-scrollbar {
    width: 6px; /* 8px → 6px로 축소 */
  }
  
  .lecture-list::-webkit-scrollbar-track {
    background: #f1f1f1;
  }
  
  .lecture-list::-webkit-scrollbar-thumb {
    background: #888;
    border-radius: 4px;
  }
  
  .lecture-list::-webkit-scrollbar-thumb:hover {
    background: #555;
  }

  /* 강의 레벨 버튼 */
.level-btn {
    padding: 14px 40px;
    border: 2px solid #d1d5db;
    background: white;
    color: #6b7280;
    font-weight: 600;
    font-size: 16px;
    border-radius: 10px;
    cursor: pointer;
    transition: all 0.3s ease;
    box-shadow: 0 2px 4px rgba(0, 0, 0, 0.05);
    position: relative;
    overflow: hidden;
  }
  
  .level-btn:hover {
    border-color: var(--active-color-light);
    color: var(--active-color-light);
    transform: translateY(-2px);
    box-shadow: 0 4px 8px rgba(59, 130, 246, 0.2);
  }
  
  .level-btn.active {
    background: linear-gradient(135deg, var(--active-color-light) 0%, var(--active-color) 100%);
    border-color: var(--active-color);
    color: white;
    box-shadow: 0 4px 12px rgba(37, 99, 235, 0.4);
  }
  
  .level-btn.active::before {
    content: '✓';
    position: absolute;
    left: 12px;
    top: 50%;
    transform: translateY(-50%);
    font-size: 14px;
    font-weight: bold;
  }
  
  /* 또는 심플한 버전 */
  .level-btn-simple {
    padding: 12px 36px;
    border: none;
    background: #f3f4f6;
    color: #6b7280;
    font-weight: 600;
    font-size: 15px;
    border-radius: 8px;
    cursor: pointer;
    transition: all 0.2s;
  }
  
  .level-btn-simple:hover {
    background: #e5e7eb;
    color: #374151;
  }
  
  .level-btn-simple.active {
    background: var(--active-color);
    color: white;
  }
  
  /* 또는 탭 스타일 버전 */
  .level-btn-tab {
    padding: 12px 32px;
    border: none;
    border-bottom: 3px solid transparent;
    background: transparent;
    color: #6b7280;
    font-weight: 600;
    font-size: 16px;
    cursor: pointer;
    transition: all 0.3s;
  }
  
  .level-btn-tab:hover {
    color: #374151;
    border-bottom-color: #d1d5db;
  }
  
  .level-btn-tab.active {
    color: var(--active-color);
    border-bottom-color: var(--active-color);
  }