*{box-sizing:border-box;margin:0;padding:0}
  :root{--bg:#f4f6f9;--card:#fff;--primary:#4a90e2;--primary-soft:#e8f1fc;--text:#2c3e50;--text-sub:#7b8a99;--border:#eef1f5;--shadow:0 2px 12px rgba(0,0,0,.06);--radius:16px}
  body{font-family:-apple-system,BlinkMacSystemFont,"PingFang SC","Microsoft YaHei",sans-serif;background:var(--bg);color:var(--text);min-height:100vh;padding:24px}
  .app{max-width:1440px;margin:0 auto}
  .card{background:var(--card);border-radius:var(--radius);box-shadow:var(--shadow);padding:26px}
  .header{display:flex;align-items:center;justify-content:space-between;margin-bottom:22px}
  .header h1{font-size:22px;font-weight:600}
  .back{font-size:13px;color:var(--text-sub);text-decoration:none;padding:6px 12px;background:var(--bg);border-radius:8px}
  .back:hover{background:var(--primary-soft);color:var(--primary)}
  .cols{display:grid;grid-template-columns:1fr 1fr;gap:16px}
  textarea{width:100%;min-height:500px;padding:14px;border:1px solid var(--border);border-radius:10px;font-size:14px;font-family:Consolas,monospace;resize:vertical}
  textarea:focus{outline:none;border-color:var(--primary)}
  .preview{width:100%;min-height:500px;padding:20px;border:1px solid var(--border);border-radius:10px;font-size:15px;line-height:1.7;overflow-y:auto}
  .preview h1{font-size:2em;margin:.5em 0;border-bottom:1px solid var(--border);padding-bottom:.3em}
  .preview h2{font-size:1.5em;margin:.5em 0}
  .preview h3{font-size:1.2em;margin:.5em 0}
  .preview p{margin:.6em 0}
  .preview code{background:var(--bg);padding:2px 6px;border-radius:4px;font-family:Consolas,monospace;font-size:.9em}
  .preview pre{background:var(--bg);padding:12px;border-radius:8px;overflow-x:auto}
  .preview pre code{background:none;padding:0}
  .preview blockquote{border-left:4px solid var(--primary);padding-left:14px;color:var(--text-sub);margin:.6em 0}
  .preview a{color:var(--primary)}
  .preview ul,.preview ol{padding-left:24px;margin:.6em 0}
  .preview table{border-collapse:collapse;margin:.6em 0}
  .preview th,.preview td{border:1px solid var(--border);padding:6px 12px}
  .preview img{max-width:100%}
  .btn-group{display:flex;gap:10px;margin-bottom:14px}
  .btn{padding:9px 16px;border:none;border-radius:10px;font-size:13px;cursor:pointer;background:var(--primary);color:#fff}
  .btn:hover{opacity:.88}
  .btn.ghost{background:var(--bg);color:var(--text-sub)}
  .btn.ghost:hover{background:var(--primary-soft);color:var(--primary)}
  @media(max-width:768px){.cols{grid-template-columns:1fr}textarea,.preview{min-height:300px}}