/* ═══════════════════════════════════════════════════════════════
   Sidebar rail variants
   The page shell owns the column (sticky, 100dvh, its own width).
   Everything here is internal to the rail.
     A "Paper rail"    280px  full nav + ticked "On this page"
     B "Gridline rail" 240px  compact, numbered mono toc, right rule
     C "Minimal rail"  220px  five section links, no toc label
   ═══════════════════════════════════════════════════════════════ */

.rail {
  display: flex;
  flex-direction: column;
  height: 100%;
  background: var(--color-surface);
  font-family: var(--font-sans);
}

/* Everything below the wordmark. On desktop it is the vertical body of the
   rail; on mobile it becomes the right-hand cluster of the top bar. */
.rail__stack {
  display: flex;
  flex: 1;
  min-height: 0;
  flex-direction: column;
}

/* ── Wordmark ── */
.rail__brand {
  display: flex;
  align-items: center;
  gap: 10px;
}
.rail__brand-mark {
  width: 20px;
  height: 20px;
  flex-shrink: 0;
}
.rail__brand-name {
  font-size: 15px;
  font-weight: 600;
  letter-spacing: -0.01em;
  color: var(--color-ink);
}

/* ── Primary / secondary link lists ── */
.rail__nav {
  display: flex;
  flex-direction: column;
}
.rail__link {
  position: relative;
  display: flex;
  align-items: center;
  gap: 6px;
  color: var(--color-ink-2);
  transition: color 0.15s ease;
}
.rail__link:hover {
  color: var(--color-ink);
}
.rail__link[aria-current="page"] {
  color: var(--color-ink);
  font-weight: 500;
}
.rail__ext {
  font-size: 0.85em;
  color: var(--color-ink-3);
}

/* ── Shared toc scaffolding ── */
.rail__toc {
  display: flex;
  flex-direction: column;
}
.rail__toc-item {
  display: block;
}
.rail__toc a {
  display: flex;
  align-items: center;
  color: var(--color-ink-2);
  transition: color 0.15s ease;
}
.rail__toc a:hover {
  color: var(--color-ink);
}

/* ── Foot ── */
.rail__foot {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--color-ink-3);
  transition: color 0.15s ease;
}
.rail__foot:hover {
  color: var(--color-ink-2);
}

/* ═══ B: Gridline rail ════════════════════════════════════════ */
.rail--b,
.rail--b .rail__stack {
  gap: 28px;
}
.rail--b {
  padding: 32px 24px;
  border-right: 1px solid var(--color-rule);
}
.rail--b .rail__brand-mark {
  width: 18px;
  height: 18px;
}
.rail--b .rail__nav {
  gap: 4px;
}
.rail--b .rail__link {
  font-size: 14px;
  padding-left: 12px;
}
.rail--b .rail__link::before {
  content: "";
  position: absolute;
  left: 0;
  top: 50%;
  transform: translateY(-50%);
  width: 1px;
  height: 14px;
  background: var(--color-ink);
  opacity: 0;
  transition: opacity 0.15s ease;
}
.rail--b .rail__link[aria-current="page"]::before {
  opacity: 1;
}
/* ── Quiet rail meta: star count and YC as text lines, not boxes ── */
.rail--b .rail__meta {
  display: grid;
  gap: 4px;
  margin-top: 16px;
  padding-top: 12px;
  border-top: 1px solid var(--color-rule);
}
.rail--b .rail__meta-line {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 8px;
  font-size: 12.5px;
  color: var(--color-ink-3);
  line-height: 1.6;
}
.rail--b .rail__meta-line:hover {
  color: var(--color-ink);
}
.rail--b .rail__meta-n {
  font-family: var(--font-mono);
  font-size: 11.5px;
}

.rail--b .rail__toc {
  gap: 8px;
}
.rail--b .rail__toc a {
  gap: 8px;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.04em;
  color: var(--color-ink-3);
}
.rail--b .rail__num {
  font-variant-numeric: tabular-nums;
  color: var(--color-ink-3);
  transition: color 0.15s ease;
}
.rail--b .rail__toc a[aria-current="true"],
.rail--b .rail__toc a[aria-current="true"] .rail__num {
  color: var(--color-ink);
}

/* Contact block, pinned to the bottom of the rail. */
.rail--b .rail__contact {
  margin-top: auto;
  padding-top: 20px;
  border-top: 1px solid var(--color-rule);
  display: grid;
  gap: 12px;
}
.rail--b .rail__contact-head {
  display: flex;
  align-items: center;
  gap: 10px;
}
.rail--b .rail__contact-head img {
  width: 28px;
  height: 28px;
  border-radius: 999px;
  box-shadow: 0 0 0 1px var(--color-rule);
  flex-shrink: 0;
}
.rail--b .rail__contact-head > div {
  display: flex;
  flex-direction: column;
  gap: 1px;
  min-width: 0;
}
.rail--b .rail__contact-title {
  font-size: 13px;
  font-weight: 500;
  color: var(--color-ink);
}
.rail--b .rail__contact-sub {
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--color-ink-3);
}
.rail--b .rail__contact-list {
  display: grid;
  gap: 8px;
}
.rail--b .rail__contact-list a {
  display: flex;
  flex-direction: column;
  gap: 1px;
  margin: 0 -6px;
  padding: 4px 6px;
  border-radius: 5px;
  font-size: 12.5px;
  line-height: 1.35;
  transition: background 0.15s ease;
}
.rail--b .rail__contact-list a:hover {
  background: var(--color-surface-2);
}
.rail--b .rail__contact-k {
  color: var(--color-ink);
  font-weight: 500;
}
.rail--b .rail__contact-v {
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--color-ink-3);
  overflow-wrap: anywhere;
}
.rail--b .rail__contact-list a:hover .rail__contact-v {
  color: var(--color-ink-2);
}

/* ═══ Mobile: the rail becomes a slim top bar ═══
   Brand on the left, three links and the Get started button on the right.
   Everything else in the rail (index, star pill, YC badge, contact) is hidden;
   the page body carries it. */
@media (max-width: 1023.98px) {
  .rail {
    flex-direction: row;
    align-items: center;
    justify-content: space-between;
    gap: 12px;
    height: 56px;
    padding: 0 16px;
    border-right: 0;
    border-bottom: 1px solid var(--color-rule);
  }
  .rail .rail__brand {
    margin: 0;
  }
  .rail .rail__toc,
  .rail .rail__toc-label,
  .rail .rail__divider,
  .rail .rail__foot,
  .rail .rail__contact,
  .rail .rail__secondary,
  .rail .rail__meta {
    display: none;
  }
  .rail .rail__stack {
    flex: 0 1 auto;
    flex-direction: row;
    align-items: center;
    gap: 16px;
  }
  .rail .rail__nav {
    flex-direction: row;
    align-items: center;
    gap: 14px;
  }
  .rail .rail__link {
    padding: 0;
    font-size: 14px;
    white-space: nowrap;
  }
  .rail .rail__link::before {
    display: none;
  }
}
@media (max-width: 479.98px) {
  .rail .rail__nav .rail__link:not(.rail__link--keep) {
    display: none;
  }
  .rail .rail__nav {
    gap: 12px;
  }
}