/* ============================================
   Layout — Navigation, Sections, Responsive
   ============================================ */

/* --- Navigation --- */
.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: var(--nav-height);
  background: var(--color-nav-bg);
  backdrop-filter: blur(20px);
  -webkit-backdrop-filter: blur(20px);
  border-bottom: 1px solid var(--color-border);
  z-index: 1000;
  transition: background-color var(--transition-normal), border-color var(--transition-normal);
}

.nav__inner {
  max-width: var(--max-width);
  margin: 0 auto;
  padding: 0 var(--space-xl);
  height: 100%;
  display: flex;
  align-items: center;
  justify-content: space-between;
}

.nav__logo {
  font-size: var(--text-lg);
  font-weight: 700;
  color: var(--color-text);
  letter-spacing: -0.02em;
}

.nav__links {
  display: flex;
  align-items: center;
  gap: var(--space-lg);
  list-style: none;
  padding: 0;
}

.nav__link {
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--color-text-secondary);
  text-transform: uppercase;
  letter-spacing: 0.05em;
  padding: var(--space-xs) 0;
  position: relative;
  transition: color var(--transition-fast);
}

.nav__link::after {
  content: '';
  position: absolute;
  bottom: -2px;
  left: 0;
  width: 0;
  height: 2px;
  background: var(--color-accent);
  transition: width var(--transition-normal);
  border-radius: 1px;
}

.nav__link:hover,
.nav__link.active {
  color: var(--color-accent);
}

.nav__link.active::after {
  width: 100%;
}

.nav__theme-toggle {
  background: none;
  border: none;
  cursor: pointer;
  font-size: var(--text-xl);
  color: var(--color-text-secondary);
  padding: var(--space-xs);
  border-radius: var(--border-radius-sm);
  transition: color var(--transition-fast), background-color var(--transition-fast);
  display: flex;
  align-items: center;
  justify-content: center;
  width: 36px;
  height: 36px;
}

.nav__theme-toggle:hover {
  color: var(--color-accent);
  background: var(--color-accent-light);
}

/* --- Hamburger Menu (Mobile) --- */
.nav__hamburger {
  display: none;
  flex-direction: column;
  gap: 5px;
  background: none;
  border: none;
  cursor: pointer;
  padding: var(--space-xs);
}

.nav__hamburger span {
  width: 22px;
  height: 2px;
  background: var(--color-text);
  border-radius: 1px;
  transition: transform var(--transition-fast), opacity var(--transition-fast);
}

.nav__hamburger.open span:nth-child(1) {
  transform: rotate(45deg) translate(5px, 5px);
}

.nav__hamburger.open span:nth-child(2) {
  opacity: 0;
}

.nav__hamburger.open span:nth-child(3) {
  transform: rotate(-45deg) translate(5px, -5px);
}

/* --- Sections --- */
.section {
  padding: var(--space-4xl) var(--space-xl);
  max-width: var(--max-width);
  margin: 0 auto;
}

.section:first-of-type {
  padding-top: calc(var(--nav-height) + var(--space-4xl));
}

.section__title {
  font-size: var(--text-3xl);
  margin-bottom: var(--space-2xl);
  position: relative;
  display: inline-block;
}

.section__title::after {
  content: '';
  position: absolute;
  bottom: -8px;
  left: 0;
  width: 48px;
  height: 3px;
  background: var(--color-accent);
  border-radius: 2px;
}

/* --- Footer --- */
.footer {
  padding: var(--space-2xl) var(--space-xl);
  text-align: center;
  color: var(--color-text-muted);
  font-size: var(--text-sm);
  border-top: 1px solid var(--color-border);
  max-width: var(--max-width);
  margin: 0 auto;
}

/* --- Responsive --- */
@media (max-width: 768px) {
  .nav__links {
    display: none;
    position: absolute;
    top: var(--nav-height);
    left: 0;
    right: 0;
    background: var(--color-nav-bg);
    backdrop-filter: blur(20px);
    -webkit-backdrop-filter: blur(20px);
    flex-direction: column;
    padding: var(--space-lg) var(--space-xl);
    border-bottom: 1px solid var(--color-border);
    gap: var(--space-md);
  }

  .nav__links.open {
    display: flex;
  }

  .nav__hamburger {
    display: flex;
  }

  .section {
    padding: var(--space-3xl) var(--space-md);
  }

  .section:first-of-type {
    padding-top: calc(var(--nav-height) + var(--space-3xl));
  }

  h1 { font-size: var(--text-3xl); }
  h2 { font-size: var(--text-2xl); }
}

@media (max-width: 375px) {
  .section {
    padding: var(--space-2xl) var(--space-md);
  }

  h1 { font-size: var(--text-2xl); }
}