:root {
  color-scheme: light;
  --bg: #0f172a;
  --card: #111827;
  --accent: #38bdf8;
  --text: #e2e8f0;
  --muted: #94a3b8;
  --error: #fca5a5;
}

* {
  box-sizing: border-box;
  font-family: "Noto Sans SC", "Microsoft YaHei", system-ui, sans-serif;
}

body {
  margin: 0;
  background: radial-gradient(circle at top, #1e293b 0%, #0b1120 60%);
  color: var(--text);
  min-height: 100vh;
  display: flex;
  align-items: center;
  justify-content: center;
}

.page {
  width: min(720px, 92vw);
}

.card {
  background: rgba(15, 23, 42, 0.9);
  border: 1px solid rgba(56, 189, 248, 0.25);
  box-shadow: 0 20px 60px rgba(0, 0, 0, 0.4);
  border-radius: 16px;
  padding: 32px;
}

h1 {
  margin: 0 0 8px;
  font-size: 28px;
}

.sub {
  margin: 0 0 24px;
  color: var(--muted);
}

.form {
  display: flex;
  gap: 12px;
  flex-wrap: wrap;
}

input {
  flex: 1 1 280px;
  padding: 12px 14px;
  border-radius: 10px;
  border: 1px solid rgba(148, 163, 184, 0.3);
  background: #0f172a;
  color: var(--text);
}

button {
  padding: 12px 18px;
  border-radius: 10px;
  border: none;
  background: var(--accent);
  color: #0b1120;
  font-weight: 700;
  cursor: pointer;
}

button:disabled {
  opacity: 0.6;
  cursor: not-allowed;
}

.result {
  margin-top: 24px;
  padding: 18px;
  border-radius: 12px;
  background: rgba(56, 189, 248, 0.12);
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  gap: 12px;
}

.code {
  font-size: 40px;
  letter-spacing: 4px;
  font-weight: 800;
}

.meta {
  color: var(--muted);
  font-size: 14px;
}

.error {
  margin-top: 16px;
  color: var(--error);
}

.hidden {
  display: none;
}