/* Global design tokens */
:root {
  --font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  --font-family-brand: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;

  --background: #f4f7fb;
  --color: #0f172a;
  --color2: #111827;
  --color3: #475569;

  --color-anchor: #2563eb;
  --color-hover: #1d4ed8;

  --background-fg: #ffffff;
  --background-fg2: #eef2ff;
  --border-color: #dbe3ef;

  --box-shadow: 0 1px 2px rgba(15, 23, 42, 0.08);
  --box-shadow2: 0 10px 30px rgba(37, 99, 235, 0.1);
}

:root[data-color="dark"] {
  --background: #0b1220;
  --color: #e5edf8;
  --color2: #f8fafc;
  --color3: #9cb0c7;

  --color-anchor: #8bb8ff;
  --color-hover: #b2ceff;

  --background-fg: #111b2e;
  --background-fg2: #17243b;
  --border-color: #213150;

  --box-shadow: 0 1px 2px rgba(2, 6, 23, 0.6);
  --box-shadow2: 0 10px 30px rgba(2, 6, 23, 0.45);
}

:root[data-color="night"] {
  --background: #141d2b;
  --color: #e2e8f0;
  --color2: #f8fafc;
  --color3: #a9b8cb;

  --color-anchor: #9fc5ff;
  --color-hover: #c4dcff;

  --background-fg: #1c293c;
  --background-fg2: #24344a;
  --border-color: #2f445f;

  --box-shadow: 0 1px 2px rgba(2, 6, 23, 0.6);
  --box-shadow2: 0 10px 30px rgba(2, 6, 23, 0.45);
}

body {
  background:
    radial-gradient(circle at 0% 0%, rgba(37, 99, 235, 0.1), transparent 28%),
    radial-gradient(circle at 100% 0%, rgba(20, 184, 166, 0.08), transparent 32%),
    var(--background);
}

a {
  color: var(--color-anchor);
}

a:hover {
  color: var(--color-hover);
}

h1, h2, h3, h4 {
  color: var(--color2);
  letter-spacing: -0.015em;
}

p, li {
  color: var(--color3);
}

/* Header */
#site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  background: color-mix(in srgb, var(--background-fg) 88%, transparent);
  border-bottom: 1px solid var(--border-color);
}

#site-header-brand {
  font-weight: 700;
  letter-spacing: -0.02em;
  font-size: 1.2rem;
}

#site-header-brand a {
  border-radius: 0.8rem;
  margin-left: 0.5rem;
}

#site-header-menu ul {
  gap: 0.3rem;
}

#site-header-menu a {
  border-radius: 999px;
  padding: 0.45rem 0.85rem;
  transition: background-color 0.2s ease, color 0.2s ease;
}

#site-header-menu a.active,
#site-header-menu a:hover {
  border-bottom: 0;
  background: color-mix(in srgb, var(--color-anchor) 14%, transparent);
  color: var(--color2);
}

#site-header-controls .dropdown-btn {
  border-radius: 999px;
  border: 1px solid var(--border-color);
  padding: 0.35rem 0.55rem;
  background: var(--background-fg);
}

#site-header-controls .dropdown-menu {
  border-radius: 0.9rem;
  border: 1px solid var(--border-color);
  background: var(--background-fg);
  box-shadow: var(--box-shadow2);
}

/* Home landing */
.landing-shell {
  width: min(1200px, 94vw);
  margin: 0 auto;
}

.landing-main {
  flex: 1;
  width: 100%;
  display: block;
  padding: clamp(1.4rem, 2vw, 2.2rem) 0 3rem;
}

.landing-hero {
  display: grid;
  gap: 1.5rem;
  grid-template-columns: 1fr;
  background:
    linear-gradient(140deg, color-mix(in srgb, var(--color-anchor) 9%, white), color-mix(in srgb, #14b8a6 7%, white));
  border: 1px solid var(--border-color);
  border-radius: 1.5rem;
  padding: clamp(1.25rem, 3vw, 2.4rem);
  box-shadow: var(--box-shadow2);
}

:root[data-color="dark"] .landing-hero,
:root[data-color="night"] .landing-hero {
  background:
    linear-gradient(140deg, color-mix(in srgb, var(--background-fg) 82%, #2563eb 18%), color-mix(in srgb, var(--background-fg2) 85%, #14b8a6 15%));
}

.landing-eyebrow {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  padding: 0.35rem 0.7rem;
  border-radius: 999px;
  background: color-mix(in srgb, var(--background-fg) 80%, transparent);
  border: 1px solid var(--border-color);
  font-size: 0.85rem;
  color: var(--color2);
}

.landing-hero h1 {
  margin-top: 0.8rem;
  font-size: clamp(1.7rem, 3.2vw, 3.1rem);
  line-height: 1.15;
}

.landing-lead {
  margin-top: 0.7rem;
  max-width: 48ch;
  font-size: clamp(1rem, 1.7vw, 1.15rem);
}

.landing-actions {
  margin-top: 1.25rem;
  display: flex;
  flex-wrap: wrap;
  gap: 0.7rem;
}

.btn-primary,
.btn-secondary {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  padding: 0.72rem 1rem;
  border-radius: 0.85rem;
  font-weight: 600;
  transition: transform 0.2s ease, box-shadow 0.2s ease;
}

.btn-primary {
  background: linear-gradient(120deg, #2563eb, #1d4ed8);
  color: #fff;
  border: 1px solid #1d4ed8;
}

.btn-secondary {
  background: var(--background-fg);
  color: var(--color2);
  border: 1px solid var(--border-color);
}

.btn-primary:hover,
.btn-secondary:hover {
  transform: translateY(-1px);
  box-shadow: 0 10px 20px rgba(15, 23, 42, 0.14);
}

.landing-metrics {
  margin-top: 1.2rem;
  display: grid;
  gap: 0.6rem;
  grid-template-columns: repeat(3, minmax(0, 1fr));
}

.landing-metrics li {
  list-style: none;
  background: color-mix(in srgb, var(--background-fg) 82%, transparent);
  border: 1px solid var(--border-color);
  border-radius: 0.9rem;
  padding: 0.7rem;
}

.landing-metrics strong {
  display: block;
  color: var(--color2);
  font-size: 1.2rem;
}

.landing-metrics span {
  font-size: 0.86rem;
}

.landing-hero-visual {
  display: flex;
  align-items: center;
  justify-content: center;
}

.landing-hero-visual img {
  max-width: min(100%, 560px);
  height: auto;
  border-radius: 1rem;
  border: 1px solid var(--border-color);
}

.principles-grid,
.grade-map,
.open-source-panel {
  margin-top: 1.5rem;
  background: var(--background-fg);
  border: 1px solid var(--border-color);
  border-radius: 1.2rem;
  padding: clamp(1rem, 2vw, 1.6rem);
}

.principles-grid > h2,
.grade-map h2,
.open-source-panel h2 {
  font-size: clamp(1.2rem, 2.3vw, 1.8rem);
}

.principles-items {
  margin-top: 1rem;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 0.8rem;
}

.principle-card {
  background: color-mix(in srgb, var(--background-fg2) 62%, var(--background-fg));
  border: 1px solid var(--border-color);
  border-radius: 1rem;
  padding: 0.95rem;
}

.principle-card i {
  font-size: 1.3rem;
  color: var(--color-anchor);
}

.principle-card h3 {
  margin-top: 0.5rem;
  font-size: 1.03rem;
}

.section-heading {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 0.8rem;
  flex-wrap: wrap;
}

.section-heading a {
  font-weight: 600;
}

.grade-grid {
  margin-top: 1rem;
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(230px, 1fr));
  gap: 0.85rem;
}

.grade-card {
  background: color-mix(in srgb, var(--background-fg2) 70%, var(--background-fg));
  border: 1px solid var(--border-color);
  border-radius: 1rem;
  padding: 0.95rem;
}

.grade-card h3 {
  display: flex;
  align-items: center;
  gap: 0.45rem;
  font-size: 1.05rem;
}

.grade-card i {
  color: var(--color-anchor);
}

.grade-card p {
  margin-top: 0.55rem;
}

.grade-link {
  margin-top: 0.65rem;
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  font-weight: 600;
}

.open-source-panel {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
}

/* Curriculum page */
.curriculum-shell {
  width: 100%;
}

.curriculum-main {
  width: min(1320px, 98vw);
  margin: 0 auto;
  gap: 1rem;
}

.curriculum-article {
  background: var(--background-fg);
  border: 1px solid var(--border-color);
  border-radius: 1.2rem;
  box-shadow: var(--box-shadow2);
  margin: 1.1rem auto 2.5rem;
  overflow: hidden;
}

#article-header {
  padding: 1.1rem 1.1rem 0.6rem;
  background:
    linear-gradient(155deg, color-mix(in srgb, var(--color-anchor) 10%, transparent), color-mix(in srgb, #14b8a6 8%, transparent));
}

.article-kicker {
  display: inline-flex;
  align-items: center;
  gap: 0.35rem;
  border-radius: 999px;
  border: 1px solid var(--border-color);
  background: var(--background-fg);
  color: var(--color2);
  font-size: 0.8rem;
  font-weight: 600;
  padding: 0.28rem 0.62rem;
}

#article-header h1 {
  margin-top: 0.72rem;
  font-size: clamp(1.45rem, 3vw, 2.35rem);
  line-height: 1.2;
}

.article-description {
  margin-top: 0.5rem;
  max-width: 65ch;
}

#article-nav {
  border-bottom: 1px solid var(--border-color);
  padding: 0.65rem 1rem;
}

#article-nav button {
  border: 1px solid var(--border-color);
  background: color-mix(in srgb, var(--background-fg2) 80%, var(--background-fg));
  border-radius: 0.7rem;
  padding: 0.4rem 0.65rem;
  color: var(--color2);
  font-weight: 600;
}

.curriculum-content {
  padding: 0.95rem 1.1rem 1.4rem;
  line-height: 1.65;
}

.curriculum-content h2 {
  margin-top: 1.5rem;
  margin-bottom: 0.7rem;
  font-size: clamp(1.2rem, 2.1vw, 1.6rem);
}

.curriculum-content h3 {
  margin-top: 1.2rem;
  margin-bottom: 0;
  border: 1px solid var(--border-color);
  border-bottom: 0;
  border-radius: 0.85rem 0.85rem 0 0;
  background: color-mix(in srgb, var(--background-fg2) 80%, var(--background-fg));
  padding: 0.75rem 0.9rem;
  font-size: 1.04rem;
}

.curriculum-content h3 + ul {
  margin-top: 0;
  margin-bottom: 0.8rem;
  border: 1px solid var(--border-color);
  border-radius: 0 0 0.85rem 0.85rem;
  background: var(--background-fg);
  padding: 0.9rem 1rem 0.9rem 1.4rem;
}

.curriculum-content li {
  margin-bottom: 0.55rem;
}

.curriculum-content li strong {
  color: var(--color2);
}

.curriculum-content code {
  border-radius: 0.4rem;
  border: 1px solid var(--border-color);
  background: color-mix(in srgb, var(--background-fg2) 80%, var(--background-fg));
  padding: 0.1rem 0.35rem;
}

.curriculum-overview ul {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(220px, 1fr));
  gap: 0.6rem;
  padding-left: 0;
}

.curriculum-overview ul li {
  list-style: none;
  border: 1px solid var(--border-color);
  border-radius: 0.8rem;
  background: color-mix(in srgb, var(--background-fg2) 70%, var(--background-fg));
  padding: 0.7rem 0.85rem;
}

#article-footer {
  border-top: 1px solid var(--border-color);
  padding: 0.9rem 1.1rem 1.1rem;
  display: flex;
  align-items: flex-start;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
}

#article-last-updated {
  display: inline-flex;
  align-items: center;
  gap: 0.32rem;
  color: var(--color3);
}

.article-pagination {
  display: flex;
  flex-wrap: wrap;
  justify-content: flex-end;
  gap: 0.65rem;
}

#article-prev-link,
#article-next-link {
  min-width: 175px;
  border: 1px solid var(--border-color);
  border-radius: 0.82rem;
  background: color-mix(in srgb, var(--background-fg2) 65%, var(--background-fg));
  padding: 0.55rem 0.72rem;
  display: flex;
  flex-direction: column;
  gap: 0.15rem;
}

.pagination-label {
  font-size: 0.78rem;
  color: var(--color3);
}

#article-prev-link strong,
#article-next-link strong {
  color: var(--color2);
}

/* Sidebar and TOC */
#sidebar,
#toc {
  background: var(--background-fg);
  border: 1px solid var(--border-color);
}

#sidebar .sticky,
#toc .sticky {
  padding: 1rem 0.8rem;
}

.sidebar-heading {
  margin-bottom: 0.7rem;
}

.sidebar-kicker {
  display: inline-flex;
  align-items: center;
  gap: 0.3rem;
  font-size: 0.76rem;
  color: var(--color3);
  text-transform: uppercase;
  letter-spacing: 0.06em;
}

.sidebar-section {
  display: block;
  margin-top: 0.9rem;
  margin-bottom: 0.35rem;
  font-size: 0.85rem;
  color: var(--color2);
}

.sidebar-link {
  display: block;
  border-radius: 0.62rem;
  padding: 0.42rem 0.58rem;
  margin-bottom: 0.2rem;
}

.sidebar-link.current {
  background: color-mix(in srgb, var(--color-anchor) 16%, transparent);
  color: var(--color2);
  font-weight: 600;
}

.toc-title {
  display: inline-flex;
  align-items: center;
  gap: 0.32rem;
  margin-bottom: 0.75rem;
}

#toc nav ul {
  margin: 0;
  padding-left: 0.65rem;
}

#toc nav li {
  margin-bottom: 0.35rem;
}

/* Footer */
#site-footer {
  border-top: 1px solid var(--border-color);
  background: color-mix(in srgb, var(--background-fg) 92%, transparent);
}

#site-footer a {
  transition: color 0.2s ease;
}

#site-footer-social a,
#site-footer-fund a {
  border: 1px solid transparent;
  border-radius: 0.65rem;
  padding: 0.2rem 0.38rem;
}

#site-footer-social a:hover,
#site-footer-fund a:hover {
  border-color: var(--border-color);
  background: color-mix(in srgb, var(--background-fg2) 80%, var(--background-fg));
}

/* Responsive */
@media (min-width: 960px) {
  .landing-hero {
    grid-template-columns: 1.08fr 0.92fr;
    align-items: center;
  }
}

@media (max-width: 1279px) {
  .curriculum-main {
    width: min(1040px, 96vw);
  }
}

@media (max-width: 767px) {
  .landing-main {
    padding-top: 1rem;
  }

  .landing-metrics {
    grid-template-columns: 1fr;
  }

  #article-footer {
    flex-direction: column;
  }

  .article-pagination {
    width: 100%;
    justify-content: stretch;
  }

  #article-prev-link,
  #article-next-link {
    width: 100%;
  }
}