/* Page scaffolding: container, sections, header, footer, page hero. */

.container {
  width: min(100% - 2 * var(--gutter), var(--container));
  margin-inline: auto;
}

.section {
  padding-block: var(--space-section);
}

.section--tight {
  padding-block: calc(var(--space-section) * 0.6);
}

.section--rule {
  border-top: 1px solid var(--color-border);
}

.section-head {
  display: grid;
  gap: var(--space-md);
  max-width: 44rem;
  margin-bottom: var(--space-2xl);
}

.section-head p {
  color: var(--color-muted);
  font-size: var(--text-lg);
}

.section-head--center {
  margin-inline: auto;
  text-align: center;
  justify-items: center;
}

.prose {
  max-width: var(--measure);
}

.prose > * + * {
  margin-top: var(--space-md);
}

.prose h2 {
  margin-top: var(--space-2xl);
  font-size: var(--text-xl);
  font-stretch: var(--stretch-body);
  letter-spacing: -0.012em;
}

.prose h3 {
  margin-top: var(--space-xl);
}

.prose ul,
.prose ol {
  padding-left: 1.25rem;
}

.prose li + li {
  margin-top: var(--space-2xs);
}

.prose a {
  color: var(--color-accent);
}

.split {
  display: grid;
  gap: var(--space-2xl);
}

@media (min-width: 60em) {
  .split {
    grid-template-columns: minmax(0, 5fr) minmax(0, 7fr);
    gap: var(--space-3xl);
    align-items: start;
  }

  .split--even {
    grid-template-columns: repeat(2, minmax(0, 1fr));
  }

  .split__sticky {
    position: sticky;
    top: calc(var(--header-height) + var(--space-xl));
  }
}

/* ---------------------------------------------------------------- header */

.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(5, 5, 5, 0.86);
  border-bottom: 1px solid transparent;
  transition: border-color var(--duration-fast) linear;
}

@supports (backdrop-filter: blur(1px)) {
  .site-header {
    background: rgba(5, 5, 5, 0.72);
    backdrop-filter: blur(14px) saturate(140%);
  }
}

.site-header.is-scrolled,
.site-header.is-open {
  border-bottom-color: var(--color-border);
}

/* backdrop-filter makes the header a containing block for fixed children,
   which would trap the full-screen mobile menu inside the header bar. */
.site-header.is-open {
  background: var(--color-bg);
  backdrop-filter: none;
}

.site-header__inner {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: var(--space-lg);
  min-height: var(--header-height);
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  text-decoration: none;
  font-weight: 640;
  font-stretch: 90%;
  font-size: 1.125rem;
  letter-spacing: -0.01em;
}

.brand__mark {
  color: var(--color-accent);
  flex: none;
}

.site-nav__list {
  list-style: none;
  padding: 0;
}

.site-nav__link {
  display: inline-block;
  padding: 0.35rem 0;
  color: var(--color-muted);
  font-size: var(--text-sm);
  font-weight: 500;
  text-decoration: none;
  transition: color var(--duration-fast) linear;
}

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

.site-nav__link[aria-current="page"] {
  text-decoration: underline;
  text-decoration-color: var(--color-accent);
  text-decoration-thickness: 2px;
  text-underline-offset: 0.55em;
}

.nav-toggle {
  display: none;
  align-items: center;
  gap: 0.6rem;
  padding: 0.5rem 0.9rem;
  background: transparent;
  border: 1px solid var(--color-border);
  border-radius: var(--radius-pill);
  font-size: var(--text-sm);
  font-weight: 500;
}

.nav-toggle__icon,
.nav-toggle__icon::before,
.nav-toggle__icon::after {
  display: block;
  width: 16px;
  height: 1.5px;
  background: currentColor;
  transition: transform var(--duration-fast) var(--ease-out);
}

.nav-toggle__icon {
  position: relative;
  background: transparent;
}

.nav-toggle__icon::before,
.nav-toggle__icon::after {
  content: "";
  position: absolute;
  left: 0;
}

.nav-toggle__icon::before {
  top: -3px;
}

.nav-toggle__icon::after {
  top: 3px;
}

.nav-toggle[aria-expanded="true"] .nav-toggle__icon::before {
  transform: translateY(3px) rotate(45deg);
}

.nav-toggle[aria-expanded="true"] .nav-toggle__icon::after {
  transform: translateY(-3px) rotate(-45deg);
}

@media (min-width: 60em) {
  .site-nav {
    display: flex;
    align-items: center;
    gap: var(--space-xl);
  }

  .site-nav__list {
    display: flex;
    gap: var(--space-lg);
  }
}

/* Small screens: a toggled full-screen panel. Browsers without the `scripting`
   media feature get this default too, and navigation.js makes it work. */
@media (max-width: 59.99em) {
  .nav-toggle {
    display: inline-flex;
  }

  .site-nav {
    display: none;
    position: fixed;
    inset: var(--header-height) 0 0 0;
    padding: var(--space-xl) var(--gutter);
    background: var(--color-bg);
    overflow-y: auto;
  }

  .site-header.is-open .site-nav {
    display: grid;
    align-content: start;
    gap: var(--space-xl);
  }

  .site-nav__list {
    display: grid;
  }

  .site-nav__list li {
    border-bottom: 1px solid var(--color-border);
  }

  .site-nav__link {
    display: block;
    padding: var(--space-md) 0;
    font-size: var(--text-xl);
    font-stretch: var(--stretch-display);
    color: var(--color-text);
  }

  .site-nav__cta {
    justify-self: start;
  }
}

/* Without JavaScript the toggle cannot work, so show the links inline instead. */
@media (max-width: 59.99em) and (scripting: none) {
  .nav-toggle {
    display: none;
  }

  .site-header__inner {
    flex-wrap: wrap;
    padding-block: var(--space-sm);
  }

  .site-nav {
    display: block;
    position: static;
    padding: 0;
    background: none;
    overflow: visible;
  }

  .site-nav__list {
    display: flex;
    flex-wrap: wrap;
    gap: var(--space-2xs) var(--space-md);
  }

  .site-nav__list li {
    border-bottom: 0;
  }

  .site-nav__link {
    display: inline-block;
    padding: 0.35rem 0;
    font-size: var(--text-sm);
    font-stretch: var(--stretch-body);
  }

  .site-nav__cta {
    margin-top: var(--space-sm);
  }
}

body.nav-open {
  overflow: hidden;
}

@media (min-width: 60em) {
  body.nav-open {
    overflow: visible;
  }
}

/* ---------------------------------------------------------------- page hero */

.page-hero {
  padding-block: clamp(56px, 8vw, 112px) clamp(48px, 6vw, 88px);
  border-bottom: 1px solid var(--color-border);
}

/* Width limits go on the children: a max-width here would shrink and re-centre the container. */
.page-hero__inner {
  display: grid;
  gap: var(--space-lg);
}

.page-hero__inner > h1 {
  max-width: 54rem;
}

.page-hero__lede {
  max-width: 44rem;
  color: var(--color-muted);
  font-size: var(--text-xl);
  line-height: 1.45;
}

/* ---------------------------------------------------------------- footer */

.site-footer {
  margin-top: var(--space-section);
  padding-block: var(--space-3xl) var(--space-xl);
  border-top: 1px solid var(--color-border);
  color: var(--color-muted);
  font-size: var(--text-sm);
}

.site-footer .brand {
  color: var(--color-text);
}

.site-footer__grid {
  display: grid;
  gap: var(--space-2xl);
}

.site-footer__about {
  display: grid;
  gap: var(--space-md);
  max-width: 24rem;
}

.site-footer__title {
  margin-bottom: var(--space-sm);
  color: var(--color-text);
  font-size: var(--text-sm);
  font-weight: 600;
  letter-spacing: 0;
}

.site-footer__nav ul {
  display: grid;
  gap: var(--space-xs);
  list-style: none;
  padding: 0;
}

.site-footer__nav a {
  text-decoration: none;
}

.site-footer__nav a:hover {
  color: var(--color-text);
  text-decoration: underline;
}

.site-footer__disclaimer {
  max-width: 62rem;
  margin-top: var(--space-2xl);
  padding-top: var(--space-lg);
  border-top: 1px solid var(--color-border);
}

.site-footer__meta {
  margin-top: var(--space-md);
  font-size: var(--text-xs);
}

@media (min-width: 45em) {
  .site-footer__grid {
    grid-template-columns: 2fr 1fr 1fr;
  }
}

/* The main landmark sits directly before the footer; the footer margin handles the gap. */
main > :last-child {
  margin-bottom: 0;
}