*{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:14px}
  textarea{width:100%;min-height:180px;padding:12px;border:1px solid var(--border);border-radius:10px;font-size:13px;font-family:Consolas,monospace;resize:vertical}
  textarea:focus{outline:none;border-color:var(--primary)}
  .btn-group{display:flex;gap:10px;margin:14px 0}
  .btn{padding:10px 20px;border:none;border-radius:10px;font-size:14px;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)}
  .stats{font-size:13px;color:var(--text-sub);margin-bottom:10px}
  .diff{background:var(--bg);border-radius:10px;padding:14px;font-family:Consolas,monospace;font-size:13px;white-space:pre-wrap;word-break:break-all;max-height:360px;overflow-y:auto}
  .diff .add{background:#d4edda;color:#155724;padding:1px 4px;border-radius:3px}
  .diff .del{background:#f8d7da;color:#721c24;padding:1px 4px;border-radius:3px;text-decoration:line-through}
  .toast{position:fixed;bottom:30px;left:50%;transform:translateX(-50%) translateY(20px);background:var(--text);color:#fff;padding:10px 20px;border-radius:10px;font-size:13px;opacity:0;transition:all .3s;pointer-events:none}
  .toast.show{opacity:1;transform:translateX(-50%) translateY(0)}