:root {
  --hue: 288;
}

/* === Registered custom properties ======================================== */
@property --hue {
  syntax: "<number>";
  inherits: true;
  initial-value: 288;
}

/* === Root tokens ========================================================= */
:root {
  /* Perceptual palette from one number */
  --accent-50:  oklch(95% 0.04 var(--hue));
  --accent-100: oklch(88% 0.08 var(--hue));
  --accent-200: oklch(78% 0.14 var(--hue));
  --accent-300: oklch(70% 0.18 var(--hue));
  --accent-400: oklch(62% 0.20 var(--hue));
  --accent-500: oklch(54% 0.18 var(--hue));
  --accent-600: oklch(44% 0.14 var(--hue));
  --accent-700: oklch(34% 0.10 var(--hue));
  --accent-800: oklch(24% 0.06 var(--hue));
  --accent-900: oklch(14% 0.03 var(--hue));

  --bg: oklch(10% 0.02 var(--hue));
  --bg-hero: oklch(12% 0.04 var(--hue));
  --bg-raised: oklch(16% 0.03 var(--hue));
  --bg-overlay: oklch(22% 0.04 var(--hue));
  --text: oklch(94% 0.01 var(--hue));
  --text-muted: oklch(72% 0.02 var(--hue));
  --text-dim: oklch(56% 0.03 var(--hue));
  --border: oklch(28% 0.04 var(--hue));

  --font-display: "Fraunces", Georgia, "Times New Roman", serif;
  --font-body: "Source Sans 3", system-ui, -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --font-mono: ui-monospace, SFMono-Regular, Menlo, Monaco, Consolas, monospace;

  --max-width: 75rem;
  --prose-width: 60ch;
  --radius: 0.5rem;
  --gutter: clamp(1rem, 4vw, 3rem);
  --header-height: 4rem;

  color-scheme: dark;
  interpolate-size: allow-keywords;
}

/* === Reset & base ======================================================== */
*, *::before, *::after {
  box-sizing: border-box;
}

[hidden] {
  display: none !important;
}

html {
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  font-family: var(--font-body);
  font-size: clamp(1rem, 0.95rem + 0.25vw, 1.125rem);
  line-height: 1.65;
  color: var(--text);
  background: var(--bg);
  background-image:
    radial-gradient(circle at 20% 0%, oklch(20% 0.08 var(--hue) / 0.22), transparent 45%),
    radial-gradient(circle at 80% 100%, oklch(18% 0.06 var(--hue) / 0.16), transparent 50%);
  background-attachment: fixed;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
}

/* View transitions: cross-fade the whole page */
@view-transition {
  navigation: auto;
}

::view-transition-old(root),
::view-transition-new(root) {
  animation-duration: 250ms;
}

img, picture, video, canvas, svg {
  display: block;
  max-width: 100%;
}

:focus-visible {
  outline: 2px solid var(--accent-300);
  outline-offset: 2px;
}

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

/* === Skip link =========================================================== */
.skip-link {
  position: absolute;
  top: -3rem;
  left: var(--gutter);
  z-index: 2000;
  padding: 0.5rem 1rem;
  background: var(--accent-300);
  color: oklch(12% 0.03 var(--hue));
  text-decoration: none;
  font-weight: 600;
  font-size: 0.85rem;
  border-radius: var(--radius);
  transition: top 150ms ease, transform 150ms ease;
}

.skip-link:focus {
  top: 0.5rem;
  transform: translateY(0);
}

/* === Reading progress bar ================================================ */
.reading-progress {
  position: fixed;
  inset: 0 0 auto 0;
  height: 3px;
  background: linear-gradient(90deg, var(--accent-400), var(--accent-200));
  transform-origin: left;
  z-index: 1000;
  opacity: 0.9;
}

@supports (animation-timeline: scroll(root)) {
  .reading-progress {
    animation: reading-progress linear;
    animation-timeline: scroll(root);
  }

  @keyframes reading-progress {
    from { transform: scaleX(0); }
    to { transform: scaleX(1); }
  }
}

@supports not (animation-timeline: scroll(root)) {
  .reading-progress {
    display: none;
  }
}

/* === Header & nav ======================================================== */
.site-header {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  height: var(--header-height);
  padding: 0 var(--gutter);
  background: transparent;
  border-bottom: 1px solid transparent;
  transition: background 200ms ease, border-color 200ms ease, backdrop-filter 200ms ease;
}

.site-header.is-scrolled {
  background: oklch(10% 0.02 var(--hue) / 0.88);
  backdrop-filter: blur(12px);
  border-bottom-color: var(--border);
}

.has-hero .site-header {
  color: var(--text);
}

.site-header__brand {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-family: var(--font-display);
  font-size: 1.5rem;
  font-weight: 500;
  color: var(--accent-100);
  text-decoration: none;
  letter-spacing: -0.02em;
}

.site-header__brand:hover, .site-header__brand:focus-visible {
  color: var(--accent-50);
}

.site-header__mark {
  display: inline-grid;
  place-items: center;
  width: 2rem;
  height: 2rem;
  border: 1px solid var(--accent-400);
  border-radius: 50%;
  color: var(--accent-200);
  font-size: 1rem;
}

.site-nav__menu {
  display: flex;
  flex-wrap: wrap;
  gap: 0.25rem 1.25rem;
  list-style: none;
  margin: 0;
  padding: 0;
}

.site-nav__link {
  display: block;
  padding: 0.25rem 0;
  font-size: 0.85rem;
  font-weight: 500;
  color: var(--text-muted);
  text-decoration: none;
  text-transform: uppercase;
  letter-spacing: 0.06em;
  border-bottom: 1px solid transparent;
  transition: color 150ms ease, border-color 150ms ease;
}

.site-nav__link:hover,
.site-nav__link:focus-visible,
.site-nav__link[aria-current="page"] {
  color: var(--accent-100);
  border-bottom-color: var(--accent-400);
}

.site-nav__toggle {
  display: none;
}

@media (max-width: 768px) {
  .site-nav__toggle {
    display: grid;
    place-items: center;
    width: 2.5rem;
    height: 2.5rem;
    padding: 0;
    background: transparent;
    border: 1px solid var(--border);
    border-radius: var(--radius);
    cursor: pointer;
  }

  .site-nav__hamburger {
    display: block;
    width: 1.25rem;
    height: 2px;
    background: var(--text);
    position: relative;
  }

  .site-nav__hamburger::before,
  .site-nav__hamburger::after {
    content: "";
    position: absolute;
    left: 0;
    width: 100%;
    height: 2px;
    background: var(--text);
    transition: transform 150ms ease;
  }

  .site-nav__hamburger::before { top: -6px; }
  .site-nav__hamburger::after { top: 6px; }

  .no-js .site-nav__toggle {
    display: none;
  }
  .no-js .site-nav__menu {
    display: flex;
    position: static;
    flex-direction: column;
    gap: 0;
    padding: 0.5rem 0 0;
    background: transparent;
    border: 0;
  }

  .js .site-nav__menu {
    display: none;
    position: absolute;
    top: var(--header-height);
    left: 0;
    right: 0;
    flex-direction: column;
    gap: 0;
    padding: 1rem var(--gutter);
    background: var(--bg-raised);
    border-bottom: 1px solid var(--border);
  }

  .js .site-nav__menu.is-open {
    display: flex;
  }

  .site-nav__link {
    display: block;
    padding: 0.75rem 0;
    border-bottom: 1px solid var(--border);
  }

  .site-nav__toggle[aria-expanded="true"] .site-nav__hamburger {
    background: transparent;
  }
  .site-nav__toggle[aria-expanded="true"] .site-nav__hamburger::before {
    transform: translateY(6px) rotate(45deg);
  }
  .site-nav__toggle[aria-expanded="true"] .site-nav__hamburger::after {
    transform: translateY(-6px) rotate(-45deg);
  }
}

/* === Main & prose layout ================================================= */
main {
  flex: 1 0 auto;
  width: 100%;
  container-type: inline-size;
}

main > .prose {
  max-width: var(--prose-width);
  margin: 0 auto;
  padding: 7rem var(--gutter) 5rem;
}

.prose > * + * {
  margin-block-start: 1.25rem;
}

.prose h1, .prose h2, .prose h3, .prose h4,
.section__inner h1, .section__inner h2, .section__inner h3, .section__inner h4 {
  font-family: var(--font-display);
  font-weight: 500;
  line-height: 1.15;
  color: var(--accent-100);
  text-wrap: balance;
  margin-block: 2rem 0.75rem;
  scroll-margin-top: calc(var(--header-height) + 1rem);
}

.prose h1, .section__inner h1 {
  font-size: clamp(2rem, 5.5cqw, 3.5rem);
  font-weight: 400;
  margin-block-start: 0;
}

.prose h2, .section__inner h2 {
  font-size: clamp(1.5rem, 3.8cqw, 2.25rem);
}

.prose h3, .section__inner h3 {
  font-size: clamp(1.2rem, 2.8cqw, 1.6rem);
}

.prose p, .prose ul, .prose ol, .prose dl,
.section__inner p, .section__inner ul, .section__inner ol, .section__inner dl {
  margin-block: 0 1.25rem;
}

.prose p, .section__inner p, .section__inner li {
  text-wrap: pretty;
}

.prose a, .section__inner a {
  color: var(--accent-200);
  text-underline-offset: 0.2em;
  text-decoration-thickness: 1px;
  transition: color 150ms ease;
}

.prose a:hover, .prose a:focus-visible,
.section__inner a:hover, .section__inner a:focus-visible {
  color: var(--accent-100);
}

.prose ul, .prose ol,
.section__inner ul, .section__inner ol {
  padding-inline-start: 1.5rem;
}

.prose li + li, .section__inner li + li {
  margin-block-start: 0.5rem;
}

.prose hr, .section__inner hr {
  border: 0;
  height: 1px;
  background: linear-gradient(90deg, transparent, var(--border), transparent);
  margin-block: 2.5rem;
}

.prose blockquote, .section__inner blockquote {
  margin-inline: 0;
  margin-block: 2rem;
  padding: 1rem 0 1rem 1.5rem;
  border-left: 2px solid var(--accent-400);
  color: var(--text-muted);
  font-style: italic;
}

.prose code, .section__inner code {
  font-family: var(--font-mono);
  font-size: 0.9em;
  padding: 0.15em 0.35em;
  background: var(--bg-overlay);
  border-radius: 0.25rem;
}

/* Drop caps on article lead paragraphs */
.prose > p:first-of-type::first-letter,
.section__inner > p:first-of-type::first-letter {
  font-family: var(--font-display);
  font-size: 3.2em;
  float: left;
  line-height: 0.8;
  padding-right: 0.1em;
  color: var(--accent-200);
  font-variation-settings: "WONK" 1, "SOFT" 50;
}

/* === Hero ================================================================ */
.hero {
  display: grid;
  place-items: center;
  min-height: 100vh;
  padding: clamp(5rem, 12vw, 8rem) var(--gutter) 4rem;
  text-align: center;
  background: var(--bg-hero);
  background-image:
    radial-gradient(ellipse at center, oklch(24% 0.08 var(--hue) / 0.35) 0%, transparent 60%),
    radial-gradient(circle at 30% 20%, oklch(22% 0.10 var(--hue) / 0.25), transparent 40%),
    radial-gradient(circle at 70% 80%, oklch(20% 0.08 var(--hue) / 0.20), transparent 45%);
  position: relative;
  overflow: hidden;
}

.hero__content {
  position: relative;
  z-index: 1;
  max-width: 52rem;
}

.hero h1 {
  margin-block-start: 0;
  font-size: clamp(2.5rem, 7vw, 5rem);
  font-weight: 400;
  line-height: 1.05;
  letter-spacing: -0.02em;
  color: var(--accent-50);
}

.hero__subtitle {
  font-size: clamp(1rem, 2vw, 1.35rem);
  color: var(--text-muted);
  max-width: 42rem;
  margin: 1rem auto 2.5rem;
  line-height: 1.55;
}

.hero__cta {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 1rem;
}

/* === Buttons ============================================================= */
.button {
  display: inline-flex;
  align-items: center;
  justify-content: center;
  min-width: 10rem;
  padding: 0.9rem 1.75rem;
  font-family: var(--font-body);
  font-size: 0.75rem;
  font-weight: 600;
  text-transform: uppercase;
  letter-spacing: 0.15em;
  color: var(--accent-100);
  background: transparent;
  border: 1px solid var(--accent-400);
  border-radius: var(--radius);
  text-decoration: none;
  cursor: pointer;
  transition: background 150ms ease, color 150ms ease, border-color 150ms ease, transform 120ms ease;
}

.button:hover, .button:focus-visible {
  background: var(--accent-500);
  border-color: var(--accent-500);
  color: oklch(12% 0.03 var(--hue));
  transform: translateY(-1px);
}

.button--filled {
  background: var(--accent-300);
  border-color: var(--accent-300);
  color: oklch(12% 0.03 var(--hue));
}

.button--filled:hover, .button--filled:focus-visible {
  background: var(--accent-200);
  border-color: var(--accent-200);
  color: oklch(10% 0.03 var(--hue));
}

/* === Sections ============================================================ */
.section {
  padding: 5rem var(--gutter);
}

.section__inner {
  max-width: var(--prose-width);
  margin-inline: auto;
}

/* Scroll-driven fade-in */
@supports (animation-timeline: view()) {
  .section {
    animation: section-reveal linear both;
    animation-timeline: view();
    animation-range: entry 0% entry 40%;
  }

  @keyframes section-reveal {
    from {
      opacity: 0;
      transform: translateY(24px);
    }
    to {
      opacity: 1;
      transform: translateY(0);
    }
  }
}

/* === Card list =========================================================== */
.card-list {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(18rem, 1fr));
  gap: 1.5rem;
  margin-block: 2.5rem 1rem;
}

.card {
  display: block;
  padding: 1.75rem;
  background: var(--bg-raised);
  border: 1px solid var(--border);
  border-radius: var(--radius);
  text-decoration: none;
  color: var(--text);
  transition: transform 150ms ease, border-color 150ms ease, box-shadow 150ms ease;
}

.card:hover, .card:focus-visible {
  transform: translateY(-4px);
  border-color: var(--accent-400);
  box-shadow: 0 12px 32px oklch(8% 0.04 var(--hue) / 0.35);
}

.card h2 {
  margin-block: 0 0.75rem;
  font-size: 1.5rem;
  color: var(--accent-100);
}

.card p {
  margin-block-end: 0;
  color: var(--text-muted);
}

/* === Grading labels ====================================================== */
.grade {
  display: inline-block;
  padding: 0.15em 0.55em;
  font-family: var(--font-mono);
  font-size: 0.72em;
  font-weight: 700;
  letter-spacing: 0.04em;
  text-transform: uppercase;
  border-radius: 999px;
  vertical-align: middle;
  white-space: nowrap;
}

.grade--established    { background: oklch(60% 0.12 145); color: oklch(12% 0.03 145); }
.grade--documented     { background: oklch(60% 0.10 220); color: oklch(12% 0.03 220); }
.grade--proposed       { background: oklch(60% 0.14 280); color: oklch(12% 0.03 280); }
.grade--interpretation { background: oklch(55% 0.12 var(--hue)); color: oklch(12% 0.03 var(--hue)); }

/* === Footer ============================================================== */
.site-footer {
  padding: 3rem var(--gutter);
  border-top: 1px solid var(--border);
}

.site-footer__inner {
  max-width: var(--prose-width);
  margin-inline: auto;
  display: flex;
  flex-direction: column;
  gap: 2.5rem;
}

.grading-legend {
  padding: 1.5rem;
  background: var(--bg-overlay);
  border: 1px solid var(--border);
  border-radius: var(--radius);
}

.grading-legend h2 {
  margin-block-start: 0;
  font-size: 1.25rem;
}

.grading-legend dl {
  display: grid;
  grid-template-columns: 1fr;
  gap: 0.75rem;
  margin: 0;
}

.grading-legend dl > div {
  display: grid;
  grid-template-columns: 8rem 1fr;
  gap: 1rem;
  align-items: baseline;
}

.grading-legend dd {
  margin: 0;
  color: var(--text-muted);
}

@media (max-width: 480px) {
  .grading-legend dl > div {
    grid-template-columns: 1fr;
    gap: 0.25rem;
  }
}

.theme-lab {
  padding: 0.75rem 1rem;
  background: var(--bg-overlay);
  border: 1px solid var(--border);
  border-radius: var(--radius);
}

.theme-lab > summary {
  color: var(--accent-200);
  font-weight: 600;
}

.theme-lab__control {
  display: flex;
  align-items: center;
  gap: 1rem;
  flex-wrap: wrap;
  margin-block: 1rem;
}

.theme-lab__control input[type="range"] {
  flex: 1 1 12rem;
  accent-color: var(--accent-300);
}

.theme-lab__control output {
  font-family: var(--font-mono);
  color: var(--text-muted);
  min-width: 3.5ch;
}

.feature-probes {
  margin-block-start: 1rem;
}

.feature-probes summary {
  cursor: pointer;
  color: var(--accent-200);
  font-weight: 600;
}

.feature-probes__list {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(12rem, 1fr));
  gap: 0.5rem;
  list-style: none;
  margin: 1rem 0 0;
  padding: 0;
}

.feature-probes__list li {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  padding: 0.35rem 0.5rem;
  background: var(--bg-raised);
  border-radius: var(--radius);
  font-size: 0.95rem;
  color: var(--text-muted);
}

.feature-probes__list li::before {
  content: "";
  width: 0.6rem;
  height: 0.6rem;
  border-radius: 50%;
  background: var(--text-dim);
  flex-shrink: 0;
}

.feature-probes__list li.is-supported::before {
  background: oklch(70% 0.2 145);
  box-shadow: 0 0 8px oklch(70% 0.2 145 / 0.6);
}

.feature-probes__list li.is-unsupported::before {
  background: oklch(55% 0.16 30);
}

.site-footer__colophon {
  text-align: center;
  color: var(--text-dim);
  font-size: 0.85rem;
}

.site-footer__colophon p {
  margin-block: 0.5rem;
}

/* === Details / accordion ================================================= */
details {
  border: 1px solid var(--border);
  border-radius: var(--radius);
  padding: 0.75rem 1rem;
  background: var(--bg-raised);
}

summary {
  cursor: pointer;
  font-weight: 600;
}

@supports (interpolate-size: allow-keywords) {
  details::details-content {
    block-size: 0;
    overflow: hidden;
    transition: block-size 250ms ease, content-visibility 250ms ease;
    transition-behavior: allow-discrete;
  }

  details[open]::details-content {
    block-size: auto;
  }
}

/* === 404 ================================================================= */
.page-404 {
  text-align: center;
  padding-top: 6rem;
}

/* === Print =============================================================== */
@media print {
  .site-header, .site-footer, .reading-progress, .theme-lab, .skip-link {
    display: none !important;
  }
  body { background: white; color: black; }
}

/* === Reduced motion ====================================================== */
@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after {
    animation-duration: 0.01ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.01ms !important;
    scroll-behavior: auto !important;
  }
}