:root {
  --rail-bg: #0f2a44;
  --rail-fg: #b9c7d6;
  --rail-active: #ffffff;
  --accent: #1f8fd6;
  --page-bg: #f4f6f9;
  --card-bg: #ffffff;
  --text: #1b2733;
  --muted: #5d6b78;
  --border: #dde3ea;
  font-family: "Segoe UI", Inter, Roboto, "Helvetica Neue", Arial, sans-serif;
}
* { box-sizing: border-box; }
html, body { height: 100%; margin: 0; }
body { display: flex; background: var(--page-bg); color: var(--text); }

.rail {
  width: 76px; flex: none; display: flex; flex-direction: column;
  background: var(--rail-bg); color: var(--rail-fg); padding: 12px 0;
}
.brand { display: flex; flex-direction: column; align-items: center; gap: 4px; margin-bottom: 16px; }
.env { font-size: 10px; font-weight: 700; letter-spacing: .08em; color: #ffcf5c; }
.rail ul { list-style: none; margin: 0; padding: 0; }
.rail .bottom { margin-top: auto; }
.rail a {
  display: flex; flex-direction: column; align-items: center; gap: 4px;
  padding: 10px 4px; color: inherit; text-decoration: none; font-size: 12px;
  border-left: 3px solid transparent;
}
.rail a svg { width: 24px; height: 24px; fill: none; stroke: currentColor; stroke-width: 1.8; stroke-linejoin: round; }
.rail a:hover { color: var(--rail-active); background: rgba(255,255,255,.06); }
.rail a[aria-selected="true"] { color: var(--rail-active); border-left-color: var(--accent); background: rgba(255,255,255,.10); }
.rail a:focus-visible { outline: 2px solid var(--accent); outline-offset: -2px; }

main { flex: 1; min-width: 0; position: relative; }
.frame { position: absolute; inset: 0; }
.frame iframe { width: 100%; height: 100%; border: 0; display: block; background: #fff; }

.page { max-width: 760px; padding: 32px 40px; }
.page h1 { font-size: 24px; margin: 0 0 12px; }
.lead { color: var(--muted); line-height: 1.5; margin: 0 0 20px; }
.card { background: var(--card-bg); border: 1px solid var(--border); border-radius: 10px; padding: 18px 22px; margin-bottom: 16px; line-height: 1.55; }
.card h2 { font-size: 16px; margin: 0 0 8px; display: flex; align-items: center; gap: 8px; }
.card.muted p { color: var(--muted); }
.card ol { padding-left: 20px; margin: 0 0 14px; }
.tag { font-size: 11px; font-weight: 600; padding: 2px 8px; border-radius: 999px; background: #eef1f4; color: var(--muted); }
.btn { display: inline-block; background: var(--accent); color: #fff; text-decoration: none; padding: 8px 16px; border-radius: 6px; font-weight: 600; }
.btn:focus-visible { outline: 2px solid var(--text); outline-offset: 2px; }
a { color: var(--accent); }

@media (max-width: 600px) {
  body { flex-direction: column-reverse; }
  .rail { width: 100%; flex-direction: row; padding: 0; }
  .brand { display: none; }
  .rail ul { display: flex; flex: 1; }
  .rail li { flex: 1; }
  .rail .bottom { margin-top: 0; flex: 0 0 20%; }
  .rail a { border-left: 0; border-top: 3px solid transparent; }
  .rail a[aria-selected="true"] { border-top-color: var(--accent); }
  .page { padding: 20px 16px; }
}