:root {
  --bg: #f3f3f3;
  --card: #ffffff;
  --fg: #1f1f1f;
  --muted: #6b6b6b;
  --line: #d4d4d4;
  --accent: #2b579a;
  --accent-fg: #ffffff;
  --danger: #b3261e;
}
@media (prefers-color-scheme: dark) {
  :root {
    --bg: #202020;
    --card: #2b2b2b;
    --fg: #ececec;
    --muted: #a0a0a0;
    --line: #444;
    --accent: #6ea0e6;
    --accent-fg: #101010;
    --danger: #f2a39d;
  }
}
* { box-sizing: border-box; }
html, body { height: 100%; margin: 0; }
body {
  background: var(--bg);
  color: var(--fg);
  font-family: system-ui, -apple-system, 'Segoe UI', sans-serif;
  display: flex;
  align-items: center;
  justify-content: center;
  padding: 16px;
}
main {
  width: 100%;
  max-width: 360px;
  background: var(--card);
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 32px 28px;
  text-align: center;
}
.mark {
  width: 48px;
  height: 48px;
  margin: 0 auto 14px;
  border-radius: 10px;
  background: var(--accent);
  color: var(--accent-fg);
  display: grid;
  place-items: center;
  font-weight: 700;
  letter-spacing: 0.04em;
}
h1 { font-size: 1.35rem; margin: 0 0 2px; font-weight: 600; }
.sub { margin: 0 0 22px; color: var(--muted); font-size: 0.9rem; }
form { text-align: left; display: flex; flex-direction: column; gap: 8px; }
label { font-size: 0.85rem; color: var(--muted); }
input {
  font: inherit;
  padding: 10px 12px;
  border: 1px solid var(--line);
  border-radius: 6px;
  background: transparent;
  color: var(--fg);
}
input:focus { outline: 2px solid var(--accent); outline-offset: 1px; }
button {
  font: inherit;
  margin-top: 6px;
  padding: 10px 12px;
  border: 0;
  border-radius: 6px;
  background: var(--accent);
  color: var(--accent-fg);
  font-weight: 600;
  cursor: pointer;
}
button:disabled { opacity: 0.6; cursor: default; }
#error { min-height: 1.3em; margin: 4px 0 0; color: var(--danger); font-size: 0.85rem; }