:root {
  --blue: #0b3fae;
  --blue-dark: #07307f;
  --ink: #152033;
  --muted: #63708a;
  --line: #dbe2f0;
  --bg: #eef2fa;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  min-height: 100vh;
  display: grid;
  place-items: center;
  padding: 24px;
  background: radial-gradient(circle at top, #ffffff 0%, var(--bg) 45%, #dfe6f5 100%);
  color: var(--ink);
  font: 16px/1.5 system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
}

.card {
  width: min(640px, 100%);
  background: #fff;
  border: 1px solid var(--line);
  border-radius: 20px;
  padding: 28px;
  box-shadow: 0 18px 50px rgba(21, 32, 51, .12);
}

.brand {
  display: flex;
  align-items: center;
  gap: 14px;
}

.mark {
  width: 52px;
  height: 52px;
  border-radius: 14px;
  display: grid;
  place-items: center;
  background: var(--blue);
  color: #fff;
  font-size: 26px;
  font-weight: 800;
}

h1 {
  margin: 0;
  font-size: 24px;
  line-height: 1.1;
}

.sub {
  margin: 4px 0 0;
  color: var(--muted);
  font-size: 14px;
}

.lead {
  margin: 26px 0 14px;
  font-weight: 600;
}

.choices {
  display: grid;
  gap: 12px;
}

.choice {
  display: grid;
  grid-template-columns: 1fr auto;
  gap: 2px 12px;
  padding: 16px 18px;
  border: 1px solid var(--line);
  border-radius: 14px;
  text-decoration: none;
  color: var(--ink);
  background: #fbfcff;
  transition: border-color .15s, box-shadow .15s, transform .15s;
}

.choice:hover {
  border-color: var(--blue);
  transform: translateY(-1px);
}

.choice.primary {
  border-color: var(--blue);
  background: linear-gradient(180deg, #f4f8ff, #e9f0ff);
  box-shadow: 0 8px 24px rgba(11, 63, 174, .12);
}

.os {
  font-weight: 700;
  font-size: 17px;
}

.file {
  grid-column: 1;
  color: var(--muted);
  font-size: 13px;
  font-family: ui-monospace, SFMono-Regular, Menlo, monospace;
}

.cta {
  grid-column: 2;
  grid-row: 1 / span 2;
  align-self: center;
  background: var(--blue);
  color: #fff;
  padding: 10px 14px;
  border-radius: 10px;
  font-size: 14px;
  font-weight: 600;
  white-space: nowrap;
}

.choice:hover .cta { background: var(--blue-dark); }

.detected {
  margin: 14px 0 0;
  color: var(--muted);
  font-size: 13px;
}

.note {
  margin: 22px 0 0;
  padding-top: 16px;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: 13px;
}

.checks {
  margin: 10px 0 0;
  font-size: 13px;
}

.checks a { color: var(--blue); }

@media (max-width: 520px) {
  .card { padding: 20px; }
  .choice { grid-template-columns: 1fr; }
  .cta { grid-column: 1; grid-row: auto; justify-self: start; margin-top: 8px; }
}