:root { --fg: #1a1a1a; --muted: #666; --line: #ddd; --bg: #f7f7f8; --accent: #0b5; --err: #c00; }
* { box-sizing: border-box; }
body { margin: 0; font: 15px/1.45 system-ui, -apple-system, Segoe UI, Roboto, sans-serif;
  color: var(--fg); background: var(--bg); }
header { display: flex; align-items: center; justify-content: space-between;
  padding: 12px 20px; background: #fff; border-bottom: 1px solid var(--line); }
header h1 { font-size: 18px; margin: 0; }
#user { color: var(--muted); font-size: 14px; }
main { padding: 20px; max-width: 1100px; margin: 0 auto; }
section { background: #fff; border: 1px solid var(--line); border-radius: 8px;
  margin-bottom: 24px; overflow: hidden; }
.bar { display: flex; align-items: center; justify-content: space-between;
  padding: 10px 16px; border-bottom: 1px solid var(--line); }
.bar h2 { font-size: 15px; margin: 0; }
table { width: 100%; border-collapse: collapse; }
th, td { text-align: left; padding: 8px 16px; border-bottom: 1px solid var(--line);
  font-size: 14px; }
th { color: var(--muted); font-weight: 600; }
tr.err td { background: #fff3f3; }
button { font: inherit; padding: 5px 12px; border: 1px solid var(--line);
  background: #fff; border-radius: 6px; cursor: pointer; }
button:hover { background: var(--bg); }
button.danger { color: var(--err); border-color: #f3c2c2; }
#status { position: fixed; bottom: 16px; left: 50%; transform: translateX(-50%);
  background: #333; color: #fff; padding: 10px 18px; border-radius: 8px; font-size: 14px; }
.enroll { display: flex; gap: 8px; padding: 12px 16px; border-bottom: 1px solid var(--line);
  flex-wrap: wrap; }
.enroll input { font: inherit; padding: 6px 10px; border: 1px solid var(--line);
  border-radius: 6px; flex: 1; min-width: 160px; }
#enroll-result { padding: 12px 16px; border-bottom: 1px solid var(--line); }
.code-box { background: #f0fff4; border: 1px solid #b7ebc6; border-radius: 8px; padding: 14px 18px; }
.code { font: 700 28px/1 ui-monospace, Menlo, Consolas, monospace; letter-spacing: 3px;
  color: var(--fg); }
.code-meta { color: var(--muted); font-size: 13px; margin-top: 8px; }