<div style="padding:40px;color:#cbccc6"><h1>Menger 立方体（2D 投影）</h1><p>每方块切 27，去 7 → 20 留下。</p><div style="padding:20px;background:#0d1017;border-left:3px solid #ffb454"><span class="katex-display"><span class="katex"><span class="katex-html" aria-hidden="true"><span class="base"><span class="strut" style="height:0.6944em;"></span><span class="mord text"><span class="mord">20 sub-cubes</span></span></span></span></span></span></div><p style="color:#707a8c">该页面需要 JavaScript 进行交互式可视化。</p></div>