/* ==========================================================================
   layout.css — Grid, Page Structure, Responsive Breakpoints, Header/Footer
   ========================================================================== */

/* ---------- Skip to Content ---------- */

.skip-link {
  position: absolute;
  top: -100%;
  left: var(--space-md);
  z-index: 1000;
  padding: var(--space-sm) var(--space-md);
  background-color: var(--color-text);
  color: var(--color-surface);
  font-size: var(--text-sm);
  font-weight: 500;
  border-radius: 0 0 var(--radius-sm) var(--radius-sm);
  transition: top var(--transition-fast);
}

.skip-link:focus {
  top: 0;
}

/* ---------- Container ---------- */

.container {
  width: 100%;
  max-width: var(--content-width);
  margin-left: auto;
  margin-right: auto;
  padding-left: var(--space-lg);
  padding-right: var(--space-lg);
}

/* ---------- Site Header ---------- */

.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  background-color: var(--color-surface);
  border-bottom: 1px solid var(--color-border);
}

.site-header .container {
  display: flex;
  align-items: center;
  justify-content: space-between;
  flex-wrap: wrap;
  min-height: 4rem;
}

.js-nav .site-header .container {
  flex-wrap: nowrap;
}

.site-logo {
  display: flex;
  flex-direction: column;
  align-items: flex-end;
  flex-shrink: 0;
  line-height: 1;
}

.site-logo img {
  height: 2.25rem;
  width: auto;
}

.site-logo__sub {
  font-size: var(--text-sm);
  font-weight: 600;
  color: var(--color-text-secondary);
  letter-spacing: 0.02em;
  margin-top: -0.55rem;
}

/* ---------- Navigation ---------- */

/* Hamburger button: hidden by default, injected by JS */
.nav-toggle-btn {
  display: none;
  align-items: center;
  justify-content: center;
  width: 2.5rem;
  height: 2.5rem;
  padding: 0;
  cursor: pointer;
  border: none;
  background: none;
}

.nav-toggle-btn .hamburger {
  position: relative;
  display: block;
  width: 1.25rem;
  height: 2px;
  background-color: var(--color-text);
  transition: background-color var(--transition-fast);
}

.nav-toggle-btn .hamburger::before,
.nav-toggle-btn .hamburger::after {
  content: '';
  position: absolute;
  left: 0;
  width: 100%;
  height: 2px;
  background-color: var(--color-text);
  transition: transform var(--transition-base);
}

.nav-toggle-btn .hamburger::before {
  top: -6px;
}

.nav-toggle-btn .hamburger::after {
  top: 6px;
}

/* Animate hamburger to X when open */
.nav-toggle-btn[aria-expanded="true"] .hamburger {
  background-color: transparent;
}

.nav-toggle-btn[aria-expanded="true"] .hamburger::before {
  top: 0;
  transform: rotate(45deg);
}

.nav-toggle-btn[aria-expanded="true"] .hamburger::after {
  top: 0;
  transform: rotate(-45deg);
}

/* Mobile nav: visible by default (no-JS fallback) */
.site-nav {
  border-top: 1px solid var(--color-border);
  padding: var(--space-sm) 0;
}

/* When JS is ready: hide nav on mobile until toggled open */
.js-nav .nav-toggle-btn {
  display: flex;
}

.js-nav .site-nav {
  display: none;
  position: absolute;
  top: 4rem;
  left: 0;
  right: 0;
  z-index: 200;
  background-color: var(--color-surface);
  border-top: none;
  border-bottom: 1px solid var(--color-border);
  box-shadow: var(--shadow-md);
  padding: var(--space-md) 0;
}

.js-nav .site-nav.is-open {
  display: block;
}

.site-nav__list {
  display: flex;
  flex-direction: column;
}

.site-nav__item {
  border-bottom: 1px solid var(--color-alt-bg);
}

.site-nav__item:last-child {
  border-bottom: none;
}

.site-nav__link {
  display: block;
  padding: var(--space-sm) var(--space-lg);
  font-size: var(--text-base);
  font-weight: 500;
  color: var(--color-text-secondary);
  transition: color var(--transition-fast);
}

.site-nav__link:hover,
.site-nav__link[aria-current="page"] {
  color: var(--color-primary);
}

/* ---------- Desktop Navigation ---------- */

@media (min-width: 768px) {
  .nav-toggle-btn {
    display: none !important;
  }

  .site-nav,
  .js-nav .site-nav {
    display: block;
    position: static;
    background: none;
    border: none;
    box-shadow: none;
    padding: 0;
  }

  .site-nav__list {
    flex-direction: row;
    gap: var(--space-xs);
  }

  .site-nav__item {
    border-bottom: none;
  }

  .site-nav__link {
    padding: var(--space-sm) var(--space-md);
    font-size: var(--text-sm);
    border-radius: var(--radius-sm);
  }

  .site-nav__link:hover {
    background-color: var(--color-alt-bg);
  }

  .site-nav__link[aria-current="page"] {
    color: var(--color-primary);
    background-color: var(--color-soft-accent);
  }
}

/* ---------- Main Content ---------- */

main {
  min-height: calc(100vh - 4rem - 16rem);
}

/* ---------- Section ---------- */

.section {
  padding: var(--space-3xl) 0;
}

.section--alt {
  background-color: var(--color-alt-bg);
}

.section--surface {
  background-color: var(--color-surface);
}

/* ---------- Page Header ---------- */

.page-header {
  padding: var(--space-3xl) 0 var(--space-2xl);
  border-bottom: 1px solid var(--color-border);
  margin-bottom: var(--space-2xl);
}

.page-header__title {
  margin-bottom: var(--space-sm);
}

.page-header__subtitle {
  font-size: var(--text-lg);
  color: var(--color-text-secondary);
  max-width: var(--reading-width);
}

/* ---------- Content Wrapper (reading width) ---------- */

.content-wrapper {
  max-width: var(--reading-width);
}

/* ---------- Grid System ---------- */

.grid {
  display: grid;
  gap: var(--space-xl);
}

.grid--2 {
  grid-template-columns: 1fr;
}

.grid--3 {
  grid-template-columns: 1fr;
}

@media (min-width: 640px) {
  .grid--2 {
    grid-template-columns: repeat(2, 1fr);
  }

  .grid--3 {
    grid-template-columns: repeat(2, 1fr);
  }
}

@media (min-width: 1024px) {
  .grid--3 {
    grid-template-columns: repeat(3, 1fr);
  }
}

/* ---------- Site Footer ---------- */

.site-footer {
  background-color: var(--color-text);
  color: var(--color-alt-bg);
  padding: var(--space-3xl) 0 var(--space-xl);
  margin-top: var(--space-3xl);
}

.footer-grid {
  display: grid;
  grid-template-columns: 1fr;
  gap: var(--space-2xl);
  margin-bottom: var(--space-2xl);
}

@media (min-width: 640px) {
  .footer-grid {
    grid-template-columns: 2fr 1fr 1fr;
  }
}

.footer-section__title {
  font-size: var(--text-sm);
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.05em;
  color: var(--color-text-muted);
  margin-bottom: var(--space-md);
}

.footer-section p {
  color: var(--color-border);
  font-size: var(--text-sm);
  line-height: var(--leading-relaxed);
}

.footer-nav__list {
  display: flex;
  flex-direction: column;
  gap: var(--space-sm);
}

.footer-nav__link {
  font-size: var(--text-sm);
  color: var(--color-border);
  transition: color var(--transition-fast);
}

.footer-nav__link:hover {
  color: var(--color-surface);
}

.footer-bottom {
  padding-top: var(--space-xl);
  border-top: 1px solid rgba(255, 255, 255, 0.1);
  font-size: var(--text-sm);
  color: var(--color-text-muted);
}