:root {
      --primary: #155eef;
      --primary-hover: #0e4dc4;
      --bg: #f2f4f7;
      --card: #fff;
      --border: #e5e7eb;
      --text: #101828;
      --muted: #676f83;
      --err: #b42318;
    }
    * { box-sizing: border-box; }
    body {
      margin: 0; min-height: 100vh; display: flex; align-items: center; justify-content: center;
      font-family: -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, "PingFang SC", "Microsoft YaHei", sans-serif;
      background: var(--bg); color: var(--text); font-size: 14px; padding: 24px;
    }
    .card {
      width: 100%; max-width: 400px; background: var(--card); border-radius: 12px;
      border: 1px solid var(--border); box-shadow: 0 1px 2px rgba(16,24,40,.06); padding: 28px;
    }
    h1 { margin: 0 0 6px; font-size: 20px; font-weight: 600; }
    p.sub { margin: 0 0 22px; color: var(--muted); font-size: 13px; line-height: 1.45; }
    label { display: block; font-size: 12px; color: var(--muted); margin-bottom: 4px; }
    input {
      width: 100%; padding: 10px 12px; border-radius: 8px; border: 1px solid var(--border);
      font-size: 14px; margin-bottom: 14px;
    }
    input:focus { outline: none; border-color: var(--primary); box-shadow: 0 0 0 2px rgba(21,94,239,.12); }
    .btn {
      width: 100%; padding: 10px; border-radius: 8px; border: none; font-size: 14px; font-weight: 500;
      cursor: pointer; background: var(--primary); color: #fff; margin-top: 4px;
    }
    .btn:hover { background: var(--primary-hover); }
    .btn-ghost {
      margin-top: 10px; background: #fff; color: var(--text); border: 1px solid var(--border);
    }
    .btn-ghost:hover { background: #f9fafb; }
    .err { color: var(--err); font-size: 13px; margin-top: 10px; min-height: 1.2em; }
    .err.err--ok { color: #027a48; }
    .err.err--bad { color: #b42318; }
    .backend-warn {
      display: none; margin-bottom: 16px; padding: 10px 12px; border-radius: 8px;
      background: #fef3f2; border: 1px solid #fecdca; color: #b42318; font-size: 13px; line-height: 1.5;
    }
    .backend-warn.show { display: block; }
    .hint { font-size: 12px; color: var(--muted); margin-top: 16px; line-height: 1.5; }
    code { font-size: 11px; background: #f2f4f7; padding: 2px 6px; border-radius: 4px; }