.main-container {
            max-width: 1000px;
            margin: 0 auto;
            padding: 30px 20px;
        }
        
        .page-header {
            text-align: center;
            margin-bottom: 30px;
        }
        
        .page-header h1 { font-size: 2rem; margin-bottom: 8px; }
        .page-header p { color: var(--text-light); }      
        /* ==================== 教程卡片列表 ==================== */
        .tutorial-list {
            display: grid;
            grid-template-columns: repeat(auto-fill, minmax(280px, 1fr));
            gap: 20px;
            margin-bottom: 40px;
        }
         .tutorial-list a {
            color: var(--text-light);
            text-decoration: none;
        }       
        .tutorial-card {
            background: var(--card);
            border-radius: var(--radius);
            padding: 24px;
            box-shadow: var(--shadow);
            cursor: pointer;
            transition: all 0.3s;
            border: 2px solid transparent;
        }
        
        .tutorial-card:hover {
            transform: translateY(-4px);
            box-shadow: 0 8px 24px rgba(0,0,0,0.12);
            border-color: var(--primary);
        }
        
        .tutorial-card.active {
            border-color: var(--primary);
            background: linear-gradient(135deg, #f5f7fa 0%, #e3f2fd 100%);
        }
        
        .card-icon {
            font-size: 2.5rem;
            margin-bottom: 12px;
        }
        
        .card-title {
            font-size: 1.2rem;
            font-weight: 700;
            margin-bottom: 8px;
        }
        
        .card-desc {
            color: var(--text-light);
            font-size: 0.9rem;
            line-height: 1.6;
            margin-bottom: 12px;
        }
        
        .difficulty-badge {
            display: inline-block;
            padding: 4px 12px;
            border-radius: 20px;
            font-size: 0.75rem;
            font-weight: 600;
            text-transform: uppercase;
        }
        
        .difficulty-badge.beginner { background: #d4edda; color: #155724; }
        .difficulty-badge.intermediate { background: #fff3cd; color: #856404; }
        .difficulty-badge.advanced { background: #f8d7da; color: #721c24; }
        
        /* ==================== 教程学习区 ==================== */
        .lesson-area {
            display: none;
            background: var(--card);
            border-radius: var(--radius);
            padding: 30px;
            box-shadow: var(--shadow);
            margin-bottom: 30px;
        }
        
        .lesson-area.active { display: block; }
        
        .lesson-header {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-bottom: 24px;
            padding-bottom: 16px;
            border-bottom: 2px solid var(--border);
        }
        
        .lesson-title {
            font-size: 1.5rem;
            font-weight: 700;
        }
        
        .lesson-progress {
            display: flex;
            gap: 8px;
            align-items: center;
        }
        
        .progress-dot {
            width: 10px;
            height: 10px;
            border-radius: 50%;
            background: var(--border);
            transition: all 0.3s;
        }
        
        .progress-dot.active { background: var(--primary); transform: scale(1.3); }
        .progress-dot.completed { background: var(--success); }
        
        /* ==================== 步骤内容 ==================== */
        .step-content {
            margin-bottom: 24px;
        }
        
        .step-text {
            font-size: 1.1rem;
            line-height: 1.8;
            margin-bottom: 20px;
            padding: 16px;
            background: var(--bg);
            border-radius: 8px;
            border-left: 4px solid var(--primary);
        }
        
        /* ==================== 演示网格 ==================== */
        .demo-grid-wrapper {
            display: flex;
            justify-content: center;
            margin: 20px 0;
        }
        
        .demo-grid {
            display: grid;
            grid-template-columns: repeat(9, var(--cell-size));
            grid-template-rows: repeat(9, var(--cell-size));
            gap: 0;
            background: var(--grid-bg);
            padding: 2px;
            width: fit-content;
        }
        
        .demo-cell {
            background: white;
            display: flex;
            align-items: center;
            justify-content: center;
            font-size: 1.3rem;
            font-weight: 600;
            border: 0.5px solid #bbb;
            position: relative;
            transition: all 0.3s;
        }
        
        .demo-cell:nth-child(3n):not(:nth-child(9n)) { border-right: 2px solid var(--grid-bg); }
        .demo-cell:nth-child(n+19):nth-child(-n+27),
        .demo-cell:nth-child(n+46):nth-child(-n+54) { border-bottom: 2px solid var(--grid-bg); }
        
        .demo-cell.highlight-row { background: #d5e8ff; }
        .demo-cell.highlight-col { background: #d5e8ff; }
        .demo-cell.highlight-box { background: #fff3cd; }
        .demo-cell.highlight-cell { 
            background: var(--primary); 
            color: white; 
            transform: scale(1.1);
            z-index: 10;
            box-shadow: 0 4px 12px rgba(52,152,219,0.4);
        }
        .demo-cell.highlight-pair { background: #e1bee7; }
        .demo-cell.correct { background: #d4edda; color: #155724; }
        .demo-cell.wrong { background: #f8d7da; color: #721c24; animation: shake 0.4s; }
        
        @keyframes shake {
            0%, 100% { transform: translateX(0); }
            25% { transform: translateX(-4px); }
            75% { transform: translateX(4px); }
        }
        
        /* ==================== 练习模式输入 ==================== */
        .practice-input {
            background: var(--primary);
            color: white;
            border: none;
            width: 100%;
            height: 100%;
            text-align: center;
            font-size: 1.3rem;
            font-weight: 600;
            outline: none;
        }
        
        .practice-input::-webkit-outer-spin-button,
        .practice-input::-webkit-inner-spin-button { -webkit-appearance: none; margin: 0; }
        
        /* ==================== 候选数显示 ==================== */
        .candidates-small {
            position: absolute;
            display: grid;
            grid-template-columns: repeat(3, 1fr);
            width: 100%;
            height: 100%;
            font-size: 0.5rem;
            color: var(--text-light);
            padding: 1px;
        }
        
        .candidates-small span {
            display: flex;
            align-items: center;
            justify-content: center;
        }
        
        /* ==================== 按钮组 ==================== */
        .lesson-controls {
            display: flex;
            justify-content: space-between;
            align-items: center;
            margin-top: 24px;
            padding-top: 20px;
            border-top: 1px solid var(--border);
        }
        
        .btn {
            padding: 10px 24px;
            border: none;
            border-radius: 8px;
            cursor: pointer;
            font-size: 1rem;
            font-weight: 600;
            transition: all 0.2s;
            background: var(--primary);
            color: white;
            display: inline-flex;
            align-items: center;
            gap: 8px;
        }
        
        .btn:hover { background: var(--primary-dark); transform: translateY(-1px); }
        .btn:disabled { background: var(--secondary); cursor: not-allowed; transform: none; }
        .btn.secondary { background: var(--secondary); }
        .btn.success { background: var(--success); }
        .btn.warning { background: var(--warning); }
        
        .hint-box {
            background: #fff3cd;
            border: 1px solid #ffeaa7;
            padding: 12px 16px;
            border-radius: 8px;
            margin: 16px 0;
            display: none;
        }
        
        .hint-box.show { display: block; }
        
        /* ==================== 完成画面 ==================== */
        .completion-screen {
            display: none;
            text-align: center;
            padding: 40px;
        }
        
        .completion-screen.active { display: block; }
        
        .completion-icon {
            font-size: 4rem;
            margin-bottom: 16px;
        }
        
        .completion-title {
            font-size: 1.8rem;
            font-weight: 700;
            margin-bottom: 12px;
            color: var(--success);
        }
        
        
        /* ==================== 响应式 ==================== */
        @media (max-width: 768px) {

            
            .tutorial-list { grid-template-columns: 1fr; }
            .lesson-header { flex-direction: column; gap: 16px; }
            .lesson-controls { flex-direction: column; gap: 12px; }
        }
        
        @media (max-width: 480px) {
            .demo-cell { font-size: 1.1rem; }
            .btn { padding: 8px 18px; font-size: 0.9rem; }
        }
        
        @media (prefers-color-scheme: dark) {

            
            .demo-cell { background: #1a1a2e; color: #eee; }
            .step-text { background: #0f3460; }
        }