/* ============================================
   NAV — Shared sticky nav with theme toggle
   ============================================ */
.site-nav {
  position: sticky;
  top: 0;
  z-index: 100;
  backdrop-filter: saturate(180%) blur(20px);
  -webkit-backdrop-filter: saturate(180%) blur(20px);
  background: var(--color-nav-bg);
  border-bottom: 1px solid var(--color-border-subtle);
  transition: background 300ms var(--ease-out);
}

.nav-inner {
  max-width: 1120px;
  margin: 0 auto;
  padding: 0 var(--sp-5);
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: 56px;
}

.nav-brand {
  font-weight: 700;
  font-size: var(--fs-body);
  color: var(--color-text-1);
  text-decoration: none;
  letter-spacing: -0.01em;
}

.nav-links {
  display: flex;
  align-items: center;
  gap: var(--sp-5);
  list-style: none;
}

.nav-links a {
  font-size: var(--fs-small);
  font-weight: 500;
  color: var(--color-text-2);
  text-decoration: none;
  transition: color var(--duration) var(--ease-out);
  position: relative;
}

.nav-links a::after {
  content: '';
  position: absolute;
  bottom: -2px;
  left: 0;
  width: 0;
  height: 1.5px;
  background: var(--color-accent);
  transition: width var(--duration) var(--ease-out);
}

.nav-links a:hover { color: var(--color-text-1); }
.nav-links a:hover::after { width: 100%; }

.nav-links a:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 4px;
  border-radius: 2px;
}

/* ============================================
   THEME TRIANGLE — Tri-color theme picker
   ============================================ */
.theme-triangle {
  background: none;
  border: 1px solid var(--color-border);
  cursor: pointer;
  padding: 0;
  border-radius: var(--r-s);
  transition: border-color var(--duration) var(--ease-out),
              background var(--duration) var(--ease-out);
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
}

.theme-triangle:hover {
  background: var(--color-chip-bg);
  border-color: var(--color-text-3);
}

.theme-triangle:focus-visible {
  outline: 2px solid var(--color-accent);
  outline-offset: 2px;
}

.theme-triangle svg {
  width: 22px;
  height: 20px;
}

/* Triangle segment styling */
.tri-segment {
  transition: opacity var(--duration) var(--ease-out),
              filter var(--duration) var(--ease-out);
  opacity: 0.35;
}

.tri-segment.active {
  opacity: 1;
  filter: drop-shadow(0 0 3px currentColor);
}

/* ============================================
   RESPONSIVE NAV
   ============================================ */
@media (max-width: 640px) {
  .nav-links { gap: var(--sp-4); }
}

@media (max-width: 480px) {
  .nav-links { gap: var(--sp-3); }
  .nav-links a { font-size: var(--fs-xs); }
}