<div style="padding:40px;color:#cbccc6"><h1>Cross-cap (RP² 浸入)</h1><p>另一种 RP² 浸入 R³ 的方式。</p><div style="padding:20px;background:#0d1017;border-left:3px solid #ffb454"><span class="katex-error" title="ParseError: KaTeX parse error: Expected 'EOF', got '^' at position 27: …intersecting RP^̲2 immersion}" style="color:#cc0000">\text{self-intersecting RP^2 immersion}</span></div><p style="color:#707a8c">该页面需要 JavaScript 进行交互式可视化。</p></div>