/* Scroll progress */
.scroll-progress {
  position: fixed;
  top: 0;
  left: 0;
  width: 100%;
  height: 3px;
  z-index: calc(var(--z-nav) + 1);
  background: transparent;
}

.scroll-progress-bar {
  height: 100%;
  width: 0%;
  background: var(--gradient-primary);
  box-shadow: 0 0 12px rgba(79, 140, 255, 0.6);
  transition: width 80ms linear;
}

/* Nav */
.site-nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: var(--z-nav);
  border-radius: 0;
  border-width: 0 0 1px;
  background: transparent;
  backdrop-filter: none;
  box-shadow: none;
  transition: background var(--duration-base) var(--ease-out-expo),
    border-color var(--duration-base) var(--ease-out-expo),
    box-shadow var(--duration-base) var(--ease-out-expo);
}

.site-nav.is-scrolled {
  background: color-mix(in srgb, var(--color-bg) 72%, transparent);
  backdrop-filter: blur(16px);
  -webkit-backdrop-filter: blur(16px);
  border-color: var(--color-border);
  box-shadow: var(--shadow-sm);
}

.nav-inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  height: var(--nav-height);
}

.nav-logo {
  font-family: var(--font-display);
  font-size: var(--text-lg);
  font-weight: 700;
  letter-spacing: -0.01em;
}

.nav-links ul {
  display: flex;
  align-items: center;
  gap: var(--space-6);
}

.nav-link {
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-text-secondary);
  transition: color var(--duration-fast) var(--ease-out-expo);
}

.nav-link:hover,
.nav-link.is-active {
  color: var(--color-text);
}

.nav-actions {
  display: flex;
  align-items: center;
  gap: var(--space-2);
}

.nav-icon-btn {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: var(--radius-full);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  color: var(--color-text-secondary);
  position: relative;
  overflow: hidden;
  transition: color var(--duration-fast) var(--ease-out-expo),
    border-color var(--duration-fast) var(--ease-out-expo),
    background var(--duration-fast) var(--ease-out-expo);
}

.nav-icon-btn:hover {
  color: var(--color-text);
  border-color: var(--color-accent);
  background: var(--color-surface-hover);
}

.nav-mobile-toggle {
  display: none;
  align-items: center;
  justify-content: center;
  width: 40px;
  height: 40px;
  border-radius: var(--radius-full);
  background: var(--color-surface);
  border: 1px solid var(--color-border);
  position: relative;
}

.nav-mobile-menu {
  display: none;
}

@media (max-width: 880px) {
  .nav-links {
    display: none;
  }

  .nav-mobile-toggle {
    display: inline-flex;
  }

  .nav-mobile-menu {
    display: block;
    max-height: 0;
    overflow: hidden;
    background: color-mix(in srgb, var(--color-bg) 88%, transparent);
    backdrop-filter: blur(16px);
    border-top: 1px solid transparent;
    transition: max-height var(--duration-base) var(--ease-out-expo),
      border-color var(--duration-base) var(--ease-out-expo);
  }

  .nav-mobile-menu.is-open {
    max-height: 420px;
    border-color: var(--color-border);
  }

  .nav-mobile-menu ul {
    display: flex;
    flex-direction: column;
    padding: var(--space-4) var(--space-5) var(--space-6);
    gap: var(--space-1);
  }

  .nav-link-mobile {
    display: block;
    padding: var(--space-3) 0;
    font-size: var(--text-lg);
  }
}

/* Back to top */
.back-to-top {
  position: fixed;
  right: var(--space-5);
  bottom: var(--space-5);
  z-index: var(--z-nav);
  width: 44px;
  height: 44px;
  border-radius: var(--radius-full);
  background: var(--gradient-primary);
  color: #fff;
  display: flex;
  align-items: center;
  justify-content: center;
  box-shadow: var(--shadow-md);
  opacity: 0;
  transform: translateY(12px) scale(0.9);
  pointer-events: none;
  transition: opacity var(--duration-base) var(--ease-out-expo),
    transform var(--duration-base) var(--ease-spring);
}

.back-to-top.is-visible {
  opacity: 1;
  transform: translateY(0) scale(1);
  pointer-events: auto;
}