/* Document, landmarks, typography and the layout primitives every page uses. */

html {
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--header-height) + 1rem);
}

@media (prefers-reduced-motion: reduce) {
  html {
    scroll-behavior: auto;
  }
}

body {
  margin: 0;
  background: var(--surface-0);
  color: var(--ink);
  font-family: var(--font-body);
  font-size: var(--step-0);
  overflow-x: hidden;
}

/* A quiet field of machine light behind everything, so the page never reads as
   flat black. It does not move and costs nothing. */
body::before {
  content: '';
  position: fixed;
  inset: 0;
  z-index: -1;
  pointer-events: none;
  background:
    radial-gradient(60vw 50vh at 8% -5%, color-mix(in srgb, var(--rift-blue) 9%, transparent), transparent 70%),
    radial-gradient(50vw 40vh at 100% 12%, color-mix(in srgb, var(--prime-sun) 6%, transparent), transparent 70%),
    var(--surface-0);
}

::selection {
  background: color-mix(in srgb, var(--rift-blue) 45%, transparent);
  color: #fff;
}

:focus-visible {
  outline: 2px solid var(--rift-white);
  outline-offset: 3px;
  border-radius: var(--radius-s);
}

/* --- Typography ------------------------------------------------------------ */

.display {
  font-family: var(--font-display);
  font-weight: 200;
  letter-spacing: var(--tracking-display);
  text-transform: uppercase;
  line-height: 0.98;
}

.eyebrow {
  font-family: var(--font-display);
  font-size: var(--step--1);
  font-weight: 600;
  letter-spacing: var(--tracking-eyebrow);
  text-transform: uppercase;
  color: var(--occupied-cyan);
  display: flex;
  align-items: center;
  gap: var(--space-xs);
}

.eyebrow::before {
  content: '';
  width: 2.5rem;
  height: 1px;
  background: linear-gradient(90deg, var(--rift-blue), transparent);
  flex: none;
}

.lede {
  font-size: var(--step-1);
  color: var(--ink-soft);
  max-width: 48ch;
}

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

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

.prose strong {
  color: var(--ink);
  font-weight: 600;
}

.label {
  font-family: var(--font-mono);
  font-size: var(--step--2);
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-muted);
}

a:where(.link) {
  color: var(--rift-white);
  text-decoration-color: color-mix(in srgb, var(--rift-blue) 60%, transparent);
  text-underline-offset: 0.25em;
  transition: color var(--speed-ui) var(--ease-out);
}

a:where(.link):hover {
  color: #fff;
  text-decoration-color: var(--rift-blue);
}

/* --- Layout ---------------------------------------------------------------- */

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

.shell--narrow {
  width: min(100% - var(--gutter) * 2, var(--content-max));
}

.section {
  position: relative;
  padding-block: clamp(4rem, 3rem + 7vw, 9rem);
}

.section--tight {
  padding-block: clamp(3rem, 2.4rem + 4vw, 5.5rem);
}

.section__head {
  display: flex;
  flex-direction: column;
  gap: var(--space-s);
  margin-bottom: var(--space-xl);
  max-width: 62ch;
}

.section__title {
  font-family: var(--font-display);
  font-weight: 200;
  letter-spacing: 0.045em;
  text-transform: uppercase;
  font-size: var(--step-4);
}

.section__title em {
  font-style: normal;
  color: var(--rift-white);
}

/* A hairline that reads as the seam between the two realities. */
.seam {
  height: 1px;
  border: 0;
  margin: 0;
  background: linear-gradient(
    90deg,
    transparent,
    color-mix(in srgb, var(--prime-sun) 35%, transparent) 22%,
    var(--rift-blue) 50%,
    color-mix(in srgb, var(--occupied-cyan) 35%, transparent) 78%,
    transparent
  );
  opacity: 0.55;
}

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

.skip-link {
  position: absolute;
  left: var(--space-s);
  top: var(--space-s);
  z-index: 200;
  transform: translateY(-200%);
  background: var(--surface-2);
  color: var(--ink);
  padding: var(--space-xs) var(--space-m);
  border: 1px solid var(--hairline-strong);
  border-radius: var(--radius-m);
  transition: transform var(--speed-ui) var(--ease-out);
}

.skip-link:focus-visible {
  transform: translateY(0);
}

.visually-hidden {
  position: absolute !important;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip-path: inset(50%);
  white-space: nowrap;
  border: 0;
}

/* --- Entrance reveals ------------------------------------------------------ */
/* Applied by reveal.js through IntersectionObserver. Without JavaScript nothing
   is hidden, because the `js` class is only ever added by main.js. */

.js [data-reveal] {
  opacity: 0;
  transform: translateY(22px);
  transition:
    opacity var(--speed-reveal) var(--ease-out),
    transform var(--speed-reveal) var(--ease-out);
  transition-delay: var(--reveal-delay, 0ms);
}

.js [data-reveal].is-revealed {
  opacity: 1;
  transform: none;
}

@media (prefers-reduced-motion: reduce) {
  .js [data-reveal] {
    opacity: 1;
    transform: none;
  }
}