/* ============================================================
   YOUNG BULL, global v4 nav strip
   Sits above the v4 surface-specific bars (cmd-bar / pg-bar / etc).
   Mirrors the production .yb-nav link set so the user can leave any
   v4 surface and reach Book/Map/Research/Portraits/Pro. Styled with
   v4 tokens so /styles/yb.css does not need to load (namespace rule
   from PR #39 preserved).
   ============================================================ */
.yb-v4-nav {
  position: sticky;
  top: 0;
  z-index: 40;
  background: var(--bg);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(8px);
  font-family: var(--mono);
}
html[data-yb-theme="light"] .yb-v4-nav {
  background: var(--bg);
  border-bottom: 1px solid var(--line);
}
.yb-v4-nav-inner {
  display: flex;
  align-items: center;
  gap: 28px;
  max-width: var(--col-mega);
  margin: 0 auto;
  padding: 10px 32px;
  font-size: 11px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
}
.yb-v4-mark {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  color: var(--ink);
  text-decoration: none;
  flex-shrink: 0;
}
.yb-v4-mark .yb-logo {
  width: 18px;
  height: 18px;
  color: var(--gold);
}
.yb-v4-mark b {
  font-weight: 600;
  letter-spacing: 0.16em;
}
.yb-v4-mark:hover { color: var(--gold); }
.yb-v4-mark:hover .yb-logo { color: var(--gold); }

.yb-v4-nav-links {
  display: inline-flex;
  align-items: center;
  gap: 22px;
  flex: 1;
}
.yb-v4-nav-links a {
  color: var(--ink-mute);
  text-decoration: none;
  transition: color var(--t-fast, 160ms) var(--ease, ease);
}
.yb-v4-nav-links a:hover { color: var(--ink); }
.yb-v4-nav-links a[aria-current="page"] {
  color: var(--gold);
}

.yb-v4-nav-actions {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  flex-shrink: 0;
}
.yb-v4-nav-signin {
  color: var(--ink-mute);
  text-decoration: none;
  border: 1px solid var(--line);
  padding: 5px 11px;
  border-radius: 2px;
  transition: color var(--t-fast, 160ms) var(--ease, ease), border-color var(--t-fast, 160ms) var(--ease, ease);
}
.yb-v4-nav-signin:hover {
  color: var(--gold);
  border-color: var(--gold-line);
}
.yb-v4-nav-cta {
  color: var(--bg);
  background: var(--gold);
  text-decoration: none;
  padding: 6px 12px;
  border-radius: 2px;
  font-weight: 600;
  display: inline-flex;
  align-items: center;
  gap: 6px;
  transition: opacity var(--t-fast, 160ms) var(--ease, ease);
}
.yb-v4-nav-cta:hover { opacity: 0.88; }

@media (max-width: 880px) {
  .yb-v4-nav-inner { gap: 16px; padding: 9px 16px; }
  .yb-v4-nav-links { gap: 14px; font-size: 10px; }
  .yb-v4-nav-signin { display: none; }
}
@media (max-width: 540px) {
  .yb-v4-nav-inner { gap: 10px; padding: 8px 12px; }
  /* Horizontal scroll instead of overflow off-screen.
     Hide the scrollbar in WebKit; flex-shrink:0 on each link so they
     keep their natural width inside the scrolling container. */
  .yb-v4-nav-links {
    gap: 12px;
    font-size: 9.5px;
    letter-spacing: 0.08em;
    overflow-x: auto;
    flex-wrap: nowrap;
    scrollbar-width: none;
    -webkit-overflow-scrolling: touch;
    mask-image: linear-gradient(90deg, transparent 0, #000 12px, #000 calc(100% - 16px), transparent 100%);
  }
  .yb-v4-nav-links::-webkit-scrollbar { display: none; }
  .yb-v4-nav-links a { flex-shrink: 0; }
  .yb-v4-nav-cta { padding: 5px 10px; font-size: 10px; flex-shrink: 0; }
  .yb-v4-mark b { font-size: 11px; letter-spacing: 0.12em; }
}

/* When yb-v4-nav stacks above an existing sticky surface bar
   (cmd-bar on /command, pg-bar on /compare-brief, sl-bar on /style,
   lp-bar on /v4), bump that bar down so both stay reachable. */
.yb-v4-nav ~ .cmd-bar,
.yb-v4-nav ~ .pg-bar,
.yb-v4-nav ~ .sl-bar,
.yb-v4-nav ~ .lp-bar,
.yb-v4-nav ~ .hr-bar {
  top: 40px;
}
@media (max-width: 880px) {
  .yb-v4-nav ~ .cmd-bar,
  .yb-v4-nav ~ .pg-bar,
  .yb-v4-nav ~ .sl-bar,
  .yb-v4-nav ~ .lp-bar,
  .yb-v4-nav ~ .hr-bar {
    top: 38px;
  }
}