ulty-dot active"></span>
                    <span class="difficulty-dot"></span>
                </div>
                <button class="start-quiz-btn" data-level="进阶者">开始测验</button>
            </div>
            
            <div class="level-card" data-level="环保专家">
                <div class="level-icon">🌳</div>
                <h3>环保专家</h3>
                <p>综合环保与可持续发展</p>
                <div class="level-difficulty">
                    <span clas