/* nav.css — 顶栏
   灵感来源：编辑性站点的极简顶栏（左 logotype + 右导航，1px 下分隔线） */

.site-nav {
  position: sticky;
  top: 0;
  z-index: 20;
  background: var(--bg);
  border-bottom: 1px solid var(--rule);
}

.site-nav__inner {
  display: flex;
  align-items: center;
  height: 64px;
  gap: 24px;
}

.site-nav__lead {
  display: inline-flex;
  align-items: baseline;
  gap: 18px;
}

.site-nav__tagline {
  font-family: var(--font-sans);
  font-size: 13px;
  font-weight: 400;
  letter-spacing: 0.02em;
  color: var(--ink-3);
  padding-left: 18px;
  border-left: 1px solid var(--rule-soft);
  white-space: nowrap;
}

.site-nav__brand {
  display: inline-flex;
  align-items: baseline;
  gap: 10px;
  text-decoration: none;
  color: var(--ink);
  font-family: var(--font-mono);
  font-weight: 500;
  font-size: 22px;
  letter-spacing: -0.01em;
}
.site-nav__mark {
  flex-shrink: 0;
  color: var(--ink);
  transform: translateY(4px);
}
.brand-spark { fill: var(--accent); }
.site-nav__brand .ver {
  font-family: var(--font-mono);
  font-size: 11px;
  color: var(--ink-3);
  letter-spacing: 0.08em;
  margin-left: 4px;
  white-space: nowrap;
}

.site-nav__inner > nav {
  margin-left: auto;
}

.site-nav__links {
  display: flex;
  align-items: center;
  gap: 56px;
  list-style: none;
  margin: 0;
  padding: 0;
}
.site-nav__links a {
  text-decoration: none;
  color: var(--ink-2);
  font-size: 14px;
  white-space: nowrap;
  transition: color var(--dur-hover) var(--ease-out);
}
.site-nav__links a:hover { color: var(--accent); }

.site-nav__cta {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  padding: 8px 14px;
  border: 1px solid var(--ink);
  background: var(--ink);
  color: var(--bg) !important;
  font-size: 14px;
  text-decoration: none;
  transition: background var(--dur-hover) var(--ease-out), color var(--dur-hover) var(--ease-out), border-color var(--dur-hover) var(--ease-out);
}
.site-nav__cta:hover { background: var(--accent); border-color: var(--accent); color: var(--accent-ink) !important; }

.theme-toggle {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
  margin-left: 20px;
  padding: 0;
  background: transparent;
  border: 1px solid var(--rule-soft);
  color: var(--ink-2);
  cursor: pointer;
  transition: color var(--dur-hover) var(--ease-out), border-color var(--dur-hover) var(--ease-out);
}
.theme-toggle:hover {
  color: var(--accent);
  border-color: var(--accent);
}
.theme-toggle__sun,
.theme-toggle__moon { display: none; }
:root[data-theme="light"] .theme-toggle__moon { display: block; }
:root[data-theme="dark"]  .theme-toggle__sun  { display: block; }

.site-nav__toggle {
  display: none;
  background: transparent;
  border: 1px solid var(--rule);
  width: 40px;
  height: 40px;
  padding: 0;
  cursor: pointer;
  position: relative;
}
.site-nav__toggle span,
.site-nav__toggle span::before,
.site-nav__toggle span::after {
  content: "";
  display: block;
  position: absolute;
  left: 10px;
  right: 10px;
  height: 1px;
  background: var(--ink);
  transition: transform 160ms var(--ease-out), opacity 160ms var(--ease-out), top 160ms var(--ease-out);
}
.site-nav__toggle span { top: 50%; }
.site-nav__toggle span::before { top: -7px; }
.site-nav__toggle span::after  { top: 7px; }
.site-nav__toggle[aria-expanded="true"] span { background: transparent; }
.site-nav__toggle[aria-expanded="true"] span::before { top: 0; transform: rotate(45deg); }
.site-nav__toggle[aria-expanded="true"] span::after  { top: 0; transform: rotate(-45deg); }

@media (max-width: 1080px) {
  .site-nav__tagline { display: none; }
}

@media (max-width: 820px) {
  .site-nav__links {
    position: absolute;
    top: 64px;
    left: 0; right: 0;
    flex-direction: column;
    gap: 0;
    background: var(--bg);
    border-bottom: 1px solid var(--rule);
    padding: 12px var(--gutter);
    transform: translateY(-8px);
    opacity: 0;
    pointer-events: none;
    transition: opacity 160ms var(--ease-out), transform 160ms var(--ease-out);
  }
  .site-nav__links.is-open {
    transform: translateY(0);
    opacity: 1;
    pointer-events: auto;
  }
  .site-nav__links li {
    border-top: 1px solid var(--rule-soft);
  }
  .site-nav__links li:first-child { border-top: 0; }
  .site-nav__links a {
    display: block;
    padding: 14px 0;
    font-size: 16px;
  }
  .site-nav__cta { display: none; }
  .site-nav__toggle { display: inline-flex; align-items: center; justify-content: center; }
  .theme-toggle { margin-left: auto; margin-right: 12px; }
}