:root {
  --bg: #eceef2; --card: #f9fafb; --fg: #1a1f29; --muted: #5a6372; --rule: #d0d5dd;
  --accent: #2f6fd6; --accent-fg: #ffffff; --bad: #b2362e;
  --ui: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #0f1319; --card: #171c24; --fg: #e3e7ee; --muted: #949eae; --rule: #2a313d;
    --accent: #5b93ef; --accent-fg: #0b1220; --bad: #e0675e; color-scheme: dark;
  }
}
* { box-sizing: border-box; }
[hidden] { display: none !important; }
html, body { margin: 0; }
body { min-height: 100vh; display: grid; place-items: center; padding-inline: 16px; padding-block: 24px;
  background: var(--bg); color: var(--fg); font: 14px/1.45 var(--ui); }
.box { width: min(380px, 100%); display: grid; gap: 12px; }
.app { margin: 0; font-weight: 800; letter-spacing: .05em; font-size: 17px; }
.card { background: var(--card); border: 1px solid var(--rule); border-radius: 10px; padding: 16px; display: grid; gap: 12px; }
h1 { font-size: 18px; margin: 0; }
label { display: grid; gap: 4px; font-size: 13px; }
input { width: 100%; font: 14px var(--ui); color: var(--fg); background: var(--bg); border: 1px solid var(--rule);
  border-radius: 6px; padding: 8px; }
button { font: 600 14px var(--ui); color: var(--accent-fg); background: var(--accent); border: 0; border-radius: 6px;
  padding: 9px 12px; cursor: pointer; }
button:disabled { opacity: .6; }
input:focus-visible, button:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; }
.error { color: var(--bad); margin: 0; min-height: 1.2em; }
pre { font: 12px ui-monospace, Menlo, Consolas, monospace; background: var(--bg); border: 1px solid var(--rule);
  border-radius: 6px; padding: 8px; overflow-x: auto; margin: 0; }
.lead { margin: 0; color: var(--muted); }
.hint { margin: 0; color: var(--muted); font-size: 12px; }
p { margin: 0; }