* { box-sizing: border-box; margin: 0; padding: 0; }
  :root {
    --bg: #f4f6f9; --card: #fff; --primary: #4a90e2; --primary-soft: #e8f1fc;
    --text: #2c3e50; --text-sub: #7b8a99; --text-muted: #aab6c2;
    --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;
    display: flex; align-items: center; justify-content: center; padding: 24px;
  }
  .app { width: 100%; max-width: 1440px; }
  .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); }
  textarea {
    width: 100%; min-height: 180px; padding: 14px; border: 1.5px solid var(--border);
    border-radius: 12px; font-size: 15px; font-family: inherit; outline: none; resize: vertical;
    background: #fafbfc; line-height: 1.6;
  }
  textarea:focus { border-color: var(--primary); background: #fff; }
  .stats { display: grid; grid-template-columns: repeat(3, 1fr); gap: 12px; margin-top: 18px; }
  .stat { background: var(--bg); border-radius: 12px; padding: 16px; text-align: center; }
  .stat .num { font-size: 26px; font-weight: 700; color: var(--primary); }
  .stat .lbl { font-size: 12px; color: var(--text-sub); margin-top: 4px; }
  .clear-btn { margin-top: 14px; padding: 10px 20px; border: none; border-radius: 10px;
    background: var(--bg); color: var(--text-sub); font-size: 13px; cursor: pointer; }
  .clear-btn:hover { background: var(--primary-soft); color: var(--primary); }