/* Shared chrome: type, shell, nav, buttons, footer, utilities */

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

#top,
#method,
#surfaces,
#release,
#roadmap {
  scroll-margin-top: 64px;
}

.skip-link {
  position: absolute;
  left: var(--shell-gutter);
  top: 0.75rem;
  z-index: 1000;
  padding: 0.55rem 0.9rem;
  border-radius: var(--radius-pill);
  background: var(--bg-raised);
  color: var(--ink);
  border: 1px solid var(--line-strong);
  transform: translateY(-160%);
  transition: transform 160ms var(--ease-css);
}

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

.sr-only {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

.eyebrow {
  font-family: var(--mono);
  font-size: var(--type-mono);
  font-weight: 500;
  line-height: var(--lh-mono);
  letter-spacing: var(--track-mono);
  text-transform: uppercase;
  color: var(--ink-muted);
}

.lede,
.section-support,
.support {
  font-size: var(--type-support);
  line-height: var(--lh-support);
  color: var(--ink-muted);
  max-width: 42rem;
}

.thesis {
  font-size: var(--type-thesis);
  line-height: var(--lh-thesis);
  letter-spacing: var(--track-thesis);
  font-weight: 600;
  text-wrap: balance;
}

.section-head {
  font-size: var(--type-section);
  line-height: var(--lh-section);
  letter-spacing: var(--track-section);
  font-weight: 600;
  text-wrap: balance;
}

.stage-line {
  font-size: var(--type-stage);
  line-height: var(--lh-stage);
  letter-spacing: var(--track-stage);
  font-weight: 590;
}

.actions {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem 1rem;
  align-items: center;
}

.btn-primary,
.btn-quiet {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.45rem;
  min-height: 2.75rem;
  padding: 0.7rem 1.2rem;
  border-radius: var(--radius-pill);
  font-size: var(--type-support);
  font-weight: 500;
  line-height: 1.2;
  text-decoration: none;
  transition: transform 100ms var(--ease-css), background 180ms var(--ease-css),
    color 180ms var(--ease-css), box-shadow 180ms var(--ease-css);
}

.btn-primary {
  background: var(--accent);
  color: #fff;
  box-shadow: var(--btn-shadow);
}

.btn-quiet {
  background: transparent;
  color: var(--ink);
  border: 1px solid var(--line-strong);
}

@media (hover: hover) {
  .btn-primary:hover {
    transform: translateY(-2px);
  }

  .btn-quiet:hover {
    transform: translateY(-2px);
    background: var(--accent-soft);
  }
}

.btn-primary:active,
.btn-quiet:active {
  transform: scale(0.985);
}

/* Navigation */

.nav {
  position: sticky;
  top: 0;
  z-index: 100;
  height: var(--nav-h);
  display: flex;
  align-items: center;
  gap: 1rem;
  padding-inline: var(--shell-gutter);
  /*
   * Frosted bar: near-opaque fill + strong blur so scrolled glyphs cannot
   * remain half-legible. Fallback solid first for engines without color-mix.
   */
  /*
   * Solid matte at the bar (alpha 1) so large headings cannot print through.
   * Frost is reserved for the scroll-edge mask below; a translucent bar at
   * ~0.90 still left readable stems on section heads in both themes.
   */
  background: var(--bg);
  backdrop-filter: blur(28px) saturate(1.25);
  -webkit-backdrop-filter: blur(28px) saturate(1.25);
  box-shadow: none;
}

.nav::after {
  /* Short scroll-edge mask; starts opaque so it never prints glyph stems. */
  content: "";
  position: absolute;
  left: 0;
  right: 0;
  bottom: -20px;
  height: 20px;
  pointer-events: none;
  opacity: 0;
  background: linear-gradient(
    to bottom,
    var(--bg) 0%,
    color-mix(in srgb, var(--bg) 88%, transparent) 30%,
    color-mix(in srgb, var(--bg) 40%, transparent) 65%,
    transparent 100%
  );
  transition: opacity 180ms var(--ease-css);
}

.nav.is-scrolled::after {
  opacity: 1;
}

.brand {
  display: inline-flex;
  align-items: center;
  gap: 0.55rem;
  flex: 0 0 auto;
  font-weight: 600;
  font-size: var(--type-support);
  letter-spacing: -0.02em;
  text-decoration: none;
  color: var(--ink);
}

.brand-mark {
  display: block;
  flex: 0 0 auto;
  width: 0.9rem;
  height: 0.9rem;
}

.nav-links {
  position: relative;
  display: none;
  align-items: center;
  gap: 1.35rem;
  margin-left: 1.5rem;
  flex: 1 1 auto;
  min-width: 0;
}

.nav-links a {
  position: relative;
  z-index: 1;
  text-decoration: none;
  color: var(--ink-muted);
  font-size: var(--type-support);
  font-weight: 500;
  white-space: nowrap;
  transition: color 160ms var(--ease-css);
}

.nav-links a.is-active,
.nav-links a:hover {
  color: var(--ink);
}

.nav-underline {
  position: absolute;
  left: 0;
  bottom: -0.35rem;
  height: 1px;
  width: 0;
  background: var(--accent);
  transform: translateX(0);
  transition: transform 220ms var(--ease-css), width 220ms var(--ease-css);
  pointer-events: none;
}

.nav-actions {
  margin-left: auto;
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
}

.nav-icon {
  width: 2.5rem;
  height: 2.5rem;
  display: inline-grid;
  place-items: center;
  border-radius: var(--radius-pill);
  color: var(--ink);
}

.nav-icon svg {
  width: 1.15rem;
  height: 1.15rem;
}

.nav-icon .icon-moon {
  display: none;
}

html.dark .nav-icon .icon-sun {
  display: none;
}

html.dark .nav-icon .icon-moon {
  display: block;
}

.mobile-nav {
  position: fixed;
  inset: var(--nav-h) 0 auto 0;
  z-index: 99;
  display: grid;
  gap: 0.25rem;
  padding: 1rem var(--shell-gutter) 1.25rem;
  background: var(--bg-raised);
  border-bottom: 1px solid var(--line);
  transform: translateY(-110%);
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
  transition: transform 220ms var(--ease-css), opacity 220ms var(--ease-css),
    visibility 220ms;
}

.mobile-nav.is-open {
  transform: translateY(0);
  opacity: 1;
  visibility: visible;
  pointer-events: auto;
}

.mobile-nav a {
  display: block;
  padding: 0.85rem 0.15rem;
  text-decoration: none;
  color: var(--ink);
  font-weight: 500;
  border-bottom: 1px solid var(--line);
}

@media (min-width: 1000px) {
  .nav-links {
    display: inline-flex;
  }

  .menu-button {
    display: none;
  }

  .mobile-nav {
    display: none;
  }
}

@media (prefers-reduced-transparency: reduce) {
  .nav {
    background: var(--bg) !important;
    backdrop-filter: none !important;
    -webkit-backdrop-filter: none !important;
  }

  .nav::after {
    background: linear-gradient(
      to bottom,
      var(--bg) 0%,
      color-mix(in srgb, var(--bg) 55%, transparent) 55%,
      transparent 100%
    );
  }
}

/* Scene helpers */

.scene-labels {
  position: absolute;
  inset: 0;
  pointer-events: none;
  z-index: 2;
}

.scene-alt {
  margin: 0;
}

html.js .scene-alt {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}

[data-canvas] {
  display: block;
  width: 100%;
  height: 100%;
}

/*
 * Reveal is progressive enhancement: content is visible by default.
 * JS adds html.reveal-armed only after IntersectionObserver is confirmed.
 */
html.reveal-armed [data-reveal] {
  opacity: 0;
  transform: translateY(12px);
  transition: opacity 520ms var(--ease-css), transform 520ms var(--ease-css);
}

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

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

@media print {
  html.reveal-armed [data-reveal],
  [data-reveal] {
    opacity: 1 !important;
    transform: none !important;
    transition: none !important;
  }
}

.site-footer {
  border-top: 1px solid var(--line);
  padding: 2.5rem 0 3rem;
}

.footer-grid {
  display: grid;
  gap: 1rem;
  align-items: start;
}

.footer-grid p,
.footer-grid small {
  color: var(--ink-muted);
}

.footer-links {
  display: flex;
  flex-wrap: wrap;
  gap: 0.85rem 1.25rem;
}

.footer-links a {
  text-decoration: none;
  color: var(--ink);
  font-weight: 500;
}

@media (min-width: 760px) {
  .footer-grid {
    grid-template-columns: auto 1fr auto auto;
    gap: 1.5rem;
    align-items: center;
  }
}

@media (max-width: 639px) {
  :root {
    --shell-gutter: 20px;
  }
}