.topnav {
  position: sticky;
  top: 0;
  z-index: 800;
  background: var(--panel);
  border-bottom: 1px solid var(--line);
}

.topnav-inner {
  max-width: 1120px;
  margin: 0 auto;
  min-height: 52px;
  display: flex;
  align-items: center;
  gap: 16px;
  padding: 0 16px;
}

.topnav-brand {
  margin: 0;
  font: 700 18px/1 var(--font-display);
  letter-spacing: .01em;
  color: var(--text);
  text-decoration: none;
  white-space: nowrap;
}
.topnav-brand b { color: var(--accent); font-weight: 700; }

.topnav-links {
  display: flex;
  align-items: center;
  gap: 2px;
}

.nav-link {
  display: inline-flex;
  align-items: center;
  height: 52px;
  padding: 0 11px;
  border-bottom: 2px solid transparent;
  color: var(--muted);
  font-size: 12.5px;
  font-weight: 600;
  text-decoration: none;
  white-space: nowrap;
  transition: color .12s, border-color .12s;
}
.nav-link:hover { color: var(--text); }
.nav-link.active { color: var(--text); border-bottom-color: var(--accent); }

.topnav-actions {
  margin-left: auto;
  display: flex;
  align-items: center;
  gap: 6px;
}

.tax-btn {
  width: 34px;
  height: 34px;
  display: grid;
  place-items: center;
  padding: 0;
  border: 1px solid var(--line);
  border-radius: var(--radius-sm);
  background: var(--panel);
  color: var(--muted);
  cursor: pointer;
  transition: border-color .12s, color .12s, background .12s;
}
.tax-btn svg { display: block; }
.tax-btn:hover {
  border-color: var(--accent);
  color: var(--accent);
  background: var(--accent-soft);
}

.theme-toggle {
  position: fixed;
  right: 16px;
  bottom: 16px;
  z-index: 900;
  width: 44px;
  height: 44px;
  display: grid;
  place-items: center;
  border: 1px solid var(--line);
  border-radius: 50%;
  background: var(--panel);
  color: var(--text);
  cursor: pointer;
  padding: 0;
  box-shadow: var(--shadow-1);
  transition: transform .15s, border-color .12s, color .12s, background .12s;
}
.theme-toggle:hover {
  border-color: var(--accent);
  color: var(--accent);
  transform: translateY(-2px);
}
.theme-toggle svg { display: none; }
html:not([data-theme="dark"]) .theme-toggle .ic-sun { display: block; }
html[data-theme="dark"] .theme-toggle .ic-moon { display: block; }