:root {
  --bg: #f6f7f9;
  --panel: #ffffff;
  --text: #1c2330;
  --muted: #5b6577;
  --border: #d5dae3;
  --accent: #2456c9;
  --ok: #1d7a3a;
  --bad: #b3261e;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #12151b;
    --panel: #1b2029;
    --text: #e6e9ef;
    --muted: #9aa4b5;
    --border: #2f3746;
    --accent: #7aa2ff;
    --ok: #5fd08a;
    --bad: #ff8a80;
  }
}
* { box-sizing: border-box; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font: 16px/1.5 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}
main {
  max-width: 640px;
  margin: 32px auto;
  padding: 24px 16px;
  background: var(--panel);
  border: 1px solid var(--border);
  border-radius: 10px;
}
h1 { font-size: 1.35rem; margin: 0 0 8px; }
h2 { font-size: 1.1rem; }
.lead, .hint { color: var(--muted); }
.hint { min-height: 1.2em; font-size: 0.9rem; margin: 4px 0 0; }
label { display: block; font-weight: 600; margin: 16px 0 4px; }
input {
  width: 100%;
  padding: 10px;
  font: inherit;
  color: var(--text);
  background: var(--bg);
  border: 1px solid var(--border);
  border-radius: 6px;
}
input:focus { outline: 2px solid var(--accent); outline-offset: 1px; }
.pair { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
@media (max-width: 520px) { .pair { grid-template-columns: 1fr; } }
details { margin-top: 16px; }
summary { cursor: pointer; color: var(--muted); }
button {
  margin-top: 20px;
  padding: 10px 18px;
  font: inherit;
  font-weight: 600;
  color: #fff;
  background: var(--accent);
  border: 0;
  border-radius: 6px;
  cursor: pointer;
}
button:disabled { opacity: 0.6; cursor: wait; }
code { font-family: ui-monospace, Menlo, Consolas, monospace; }
.result { word-break: break-all; }
.result.ok { color: var(--ok); }
.result.bad { color: var(--bad); }