*{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)}
  label{display:block;font-size:13px;color:var(--text-sub);margin-bottom:6px}
  textarea{width:100%;min-height:140px;padding:12px;border:1px solid var(--border);border-radius:10px;font-size:14px;resize:vertical}
  textarea:focus{outline:none;border-color:var(--primary)}
  .row{display:flex;gap:10px;align-items:center;margin:14px 0}
  .row label{font-size:14px;color:var(--text);margin-bottom:0}
  .row input{width:80px;padding:8px 10px;border:1px solid var(--border);border-radius:8px;font-size:13px}
  .display{background:linear-gradient(135deg,var(--primary),#6aa9e9);border-radius:16px;padding:40px 20px;color:#fff;text-align:center;font-size:36px;font-weight:700;min-height:140px;display:flex;align-items:center;justify-content:center;margin:16px 0;word-break:break-all}
  .display.small{font-size:22px;flex-direction:column;gap:10px}
  .btn-group{display:flex;gap:10px;justify-content:center}
  .btn{padding:12px 30px;border:none;border-radius:12px;font-size:16px;cursor:pointer;background:var(--primary);color:#fff;font-weight:600}
  .btn:hover{opacity:.88}
  .btn.ghost{background:var(--bg);color:var(--text-sub);padding:12px 20px}
  .btn.ghost:hover{background:var(--primary-soft);color:var(--primary)}
  .history{margin-top:16px;font-size:13px;color:var(--text-sub);min-height:20px}