:root {
  --purple: #361a54;
  --purple-deep: #26113d;
  --purple-soft: #f4f0f7;
  --purple-mid: #75558f;
  --yellow: #fdd633;
  --yellow-deep: #8a6800;
  --yellow-soft: #fff9df;
  --ink: #19171c;
  --muted: #625d68;
  --line: #ded9e2;
  --paper: #fffefa;
  --white: #ffffff;
  --max-width: 1180px;
  --content-width: 820px;
  --header-height: 74px;
  --section-nav-height: 60px;
}

*, *::before, *::after { box-sizing: border-box; }

html {
  scroll-behavior: smooth;
  scroll-padding-top: calc(var(--header-height) + var(--section-nav-height) + 22px);
  background: var(--purple-deep);
}

body {
  margin: 0;
  color: var(--ink);
  background: var(--paper);
  font-family: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif;
  font-size: 17px;
  line-height: 1.72;
  text-rendering: optimizeLegibility;
  -webkit-font-smoothing: antialiased;
}

img { display: block; max-width: 100%; height: auto; }
button, input { font: inherit; }

a {
  color: var(--purple);
  text-decoration-thickness: 1px;
  text-underline-offset: 0.2em;
}

a:hover { text-decoration-thickness: 2px; }

:focus-visible {
  outline: 3px solid var(--yellow);
  outline-offset: 4px;
  border-radius: 2px;
}

::selection { background: var(--yellow); color: var(--purple-deep); }

.wide-container {
  width: min(100% - 48px, var(--max-width));
  margin-inline: auto;
}

.skip-link {
  position: fixed;
  top: 10px;
  left: 10px;
  z-index: 999;
  padding: 0.7rem 1rem;
  color: var(--white);
  background: var(--purple);
  transform: translateY(-160%);
}

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

h1, h2, h3 {
  margin: 0;
  color: var(--purple-deep);
  line-height: 1.14;
  letter-spacing: -0.035em;
}

h1 { font-size: clamp(2.55rem, 5vw, 5rem); font-weight: 800; }
h2 { font-size: clamp(2.15rem, 4vw, 3.65rem); font-weight: 750; }
h3 { font-size: clamp(1.22rem, 2vw, 1.48rem); letter-spacing: -0.02em; }

p { margin: 0 0 1.25rem; }
strong { font-weight: 700; }
code {
  padding: 0.12rem 0.38rem;
  border-radius: 3px;
  color: var(--purple);
  background: var(--purple-soft);
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.88em;
}

.eyebrow {
  margin: 0 0 0.7rem;
  color: var(--purple-mid);
  font-size: 0.76rem;
  font-weight: 800;
  line-height: 1.4;
  letter-spacing: 0.16em;
  text-transform: uppercase;
}

.lede {
  margin-bottom: 1.6rem;
  color: #37313c;
  font-size: clamp(1.14rem, 1.5vw, 1.28rem);
  line-height: 1.62;
  letter-spacing: -0.012em;
}

/* Header */
.site-header {
  position: sticky;
  top: 0;
  z-index: 100;
  min-height: var(--header-height);
  color: var(--white);
  background: var(--purple);
  border-bottom: 1px solid rgba(255, 255, 255, 0.13);
}

.header-inner {
  min-height: var(--header-height);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 2rem;
}

.challenge-brand {
  display: flex;
  flex-direction: column;
  gap: 0.05rem;
  color: var(--white);
  line-height: 1.2;
  text-decoration: none;
}

.challenge-brand span {
  font-size: 0.68rem;
  font-weight: 700;
  letter-spacing: 0.13em;
  text-transform: uppercase;
  opacity: 0.76;
}

.challenge-brand strong { font-size: 1rem; letter-spacing: -0.01em; }

.primary-nav { display: flex; align-items: center; gap: 1.75rem; }
.primary-nav a {
  color: var(--white);
  font-size: 0.9rem;
  font-weight: 650;
  text-decoration: none;
}
.primary-nav > a:first-child:hover { text-decoration: underline; text-decoration-color: var(--yellow); }
.primary-nav .github-link {
  display: inline-flex;
  align-items: center;
  gap: 0.52rem;
  padding: 0.58rem 0.82rem;
  border: 1px solid rgba(255, 255, 255, 0.48);
  border-radius: 5px;
}
.primary-nav .github-link:hover { border-color: var(--yellow); }
.primary-nav svg { width: 18px; height: 18px; }

.nav-toggle {
  display: none;
  width: 42px;
  height: 42px;
  align-items: center;
  justify-content: center;
  color: var(--white);
  background: transparent;
  border: 1px solid rgba(255, 255, 255, 0.4);
  border-radius: 4px;
  cursor: pointer;
}
.nav-toggle svg { width: 21px; height: 21px; }

/* Hero */
.challenge-hero {
  overflow: hidden;
  padding: clamp(4.25rem, 8vw, 8rem) 0 clamp(4rem, 7vw, 6.7rem);
  background: var(--paper);
}

.hero-layout {
  display: grid;
  grid-template-columns: repeat(2, minmax(0, 1fr));
  align-items: center;
  gap: clamp(2rem, 4vw, 4rem);
}

.hero-copy { position: relative; z-index: 1; }
.hero-copy h1 {
  max-width: 700px;
  font-size: clamp(2.65rem, 4.2vw, 4.25rem);
}
.marker-highlight {
  padding: 0.02em 0.12em;
  margin: 0 -0.06em;
  background: linear-gradient(
    to bottom,
    transparent 12%,
    var(--yellow) 12%,
    var(--yellow) 93%,
    transparent 93%
  );
  -webkit-box-decoration-break: clone;
  box-decoration-break: clone;
}
.hero-lead {
  max-width: 630px;
  margin: 1.6rem 0 2rem;
  color: var(--muted);
  font-size: clamp(1.08rem, 1.4vw, 1.23rem);
  line-height: 1.65;
}

.button-row { display: flex; flex-wrap: wrap; align-items: center; gap: 0.8rem; }
.button {
  min-height: 48px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  gap: 0.55rem;
  padding: 0.7rem 1.15rem;
  border: 1px solid var(--purple);
  border-radius: 5px;
  font-size: 0.92rem;
  font-weight: 750;
  line-height: 1;
  text-decoration: none;
  transition: background-color 150ms ease, color 150ms ease, border-color 150ms ease;
}
.button svg { width: 17px; height: 17px; }
.button-primary { color: var(--white); background: var(--purple); }
.button-primary:hover { color: var(--purple); background: var(--yellow); border-color: var(--yellow); }
.button-secondary { color: var(--purple); background: transparent; }
.button-secondary:hover { background: var(--purple-soft); }

.hero-notebook-link {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  margin-top: 1.2rem;
  font-size: 0.84rem;
  font-weight: 700;
}
.hero-notebook-link svg { width: 17px; height: 17px; }

.hero-art {
  min-width: 0;
  margin: 0;
  display: flex;
  align-items: center;
  justify-content: center;
}
.hero-art img {
  width: min(118%, 700px);
  max-width: none;
  max-height: 600px;
  object-fit: contain;
}

/* Sticky document navigation */
.section-nav {
  position: sticky;
  top: var(--header-height);
  z-index: 90;
  height: var(--section-nav-height);
  background: rgba(255, 254, 250, 0.97);
  border-top: 1px solid var(--line);
  border-bottom: 1px solid var(--line);
  backdrop-filter: blur(8px);
}
.section-nav-scroll {
  height: 100%;
  display: flex;
  align-items: stretch;
  gap: 1.9rem;
  overflow-x: auto;
  scrollbar-width: none;
}
.section-nav-scroll::-webkit-scrollbar { display: none; }
.section-nav a {
  position: relative;
  display: inline-flex;
  align-items: center;
  flex: 0 0 auto;
  color: var(--muted);
  font-size: 1rem;
  font-weight: 650;
  letter-spacing: -0.005em;
  text-decoration: none;
}
.section-nav a::after {
  content: "";
  position: absolute;
  right: 0;
  bottom: -1px;
  left: 0;
  height: 3px;
  background: transparent;
}
.section-nav a:hover, .section-nav a.active { color: var(--purple); }
.section-nav a.active::after { background: var(--purple); }

/* Documentation content */
.challenge-content { overflow: hidden; }
.doc-section {
  display: grid;
  grid-template-columns: minmax(180px, 245px) minmax(0, var(--content-width));
  justify-content: space-between;
  gap: clamp(2.5rem, 8vw, 7rem);
  padding-top: clamp(5.5rem, 9vw, 8.5rem);
  padding-bottom: clamp(5.5rem, 9vw, 8.5rem);
  border-bottom: 1px solid var(--line);
  scroll-margin-top: calc(var(--header-height) + var(--section-nav-height) + 20px);
}

.section-heading {
  display: grid;
  grid-template-columns: 32px minmax(0, 1fr);
  align-items: start;
  gap: 0.85rem;
}
.section-heading h2 { font-size: clamp(2.25rem, 4vw, 3.45rem); }
.section-number {
  margin: 0.38rem 0 0;
  color: var(--purple-mid);
  font-size: 0.72rem;
  font-weight: 750;
  letter-spacing: 0.07em;
}
.section-number svg { width: 18px; height: 18px; }
.prose-column { min-width: 0; }
.prose-column h3 { margin: 3rem 0 1rem; }
.prose-column > h3:first-child { margin-top: 0; }
.prose-column ul { padding-left: 1.25rem; }

.takeaway {
  display: grid;
  grid-template-columns: 5px minmax(0, 1fr);
  gap: 1.1rem;
  margin: 2.3rem 0;
  padding: 1.25rem 1.4rem 1.25rem 0;
  background: var(--yellow-soft);
}
.takeaway-mark { background: var(--yellow); }
.takeaway p { margin: 0; }
.takeaway .takeaway-label {
  margin-bottom: 0.2rem;
  color: var(--yellow-deep);
  font-size: 0.7rem;
  font-weight: 800;
  letter-spacing: 0.12em;
  text-transform: uppercase;
}

.team-note {
  display: grid;
  grid-template-columns: 30px minmax(0, 1fr);
  gap: 1rem;
  margin-top: 2.8rem;
  padding: 1.4rem 0;
  border-top: 3px solid var(--yellow);
  border-bottom: 1px solid var(--line);
}
.team-note > svg { width: 23px; height: 23px; margin-top: 0.15rem; color: var(--purple); }
.team-note h3 { margin: 0 0 0.45rem; }
.team-note p { margin: 0; color: var(--muted); }

/* Skills */
.skills-list {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 0 2.7rem;
  margin: 2rem 0 2.6rem;
  padding: 0 !important;
  list-style: none;
}
.skills-list li {
  display: grid;
  grid-template-columns: 5px minmax(0, 1fr);
  align-items: start;
  gap: 1.1rem;
  padding: 1.25rem 0;
  border-top: 1px solid var(--line);
}
.skills-list li:last-child, .skills-list li:nth-last-child(2):nth-child(odd) {
  border-bottom: 1px solid var(--line);
}
.skills-list .skill-mark {
  height: 1.1em;
  margin-top: 0.28em;
  background: var(--yellow);
}
.skills-list h3 { margin: 0 0 0.3rem; font-size: 1.12rem; }
.skills-list p { margin: 0; color: var(--muted); font-size: 0.96rem; line-height: 1.6; }

/* Tables */
.table-wrap {
  width: 100%;
  overflow-x: auto;
  margin: 1.7rem 0 3.2rem;
  border-top: 2px solid var(--purple);
}
table { width: 100%; border-collapse: collapse; font-size: 0.94rem; }
caption {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
}
th, td { padding: 0.9rem 1rem; text-align: left; border-bottom: 1px solid var(--line); }
th {
  color: var(--purple);
  background: var(--purple-soft);
  font-size: 0.72rem;
  font-weight: 800;
  letter-spacing: 0.07em;
  text-transform: uppercase;
  white-space: nowrap;
}
td:first-child { font-weight: 600; }

.split-list { margin: 1rem 0 3rem; }
.split-list div { padding: 1.1rem 0; border-top: 1px solid var(--line); }
.split-list div:last-child { border-bottom: 1px solid var(--line); }
.split-list dt { color: var(--purple); font-weight: 750; }
.split-list dt span {
  float: right;
  color: var(--muted);
  font-size: 0.76rem;
  font-weight: 650;
  letter-spacing: 0.03em;
}
.split-list dd { margin: 0.3rem 0 0; color: var(--muted); }

.text-link {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  font-weight: 700;
}
.text-link svg { width: 16px; height: 16px; }

/* Baselines */
.baseline-list {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 2.7rem;
  margin: 2.8rem 0 2.5rem;
}
.baseline-list > div { padding-top: 1.4rem; border-top: 3px solid var(--purple); }
.baseline-list h3 { margin: 0 0 1rem; }
.baseline-index {
  margin-bottom: 0.55rem;
  color: var(--purple-mid);
  font-size: 0.7rem;
  font-weight: 800;
  letter-spacing: 0.1em;
  text-transform: uppercase;
}
.tag-list {
  display: flex;
  flex-wrap: wrap;
  gap: 0.45rem;
  margin: 1.2rem 0 1.5rem;
  padding: 0 !important;
  list-style: none;
}
.tag-list li {
  padding: 0.28rem 0.68rem;
  color: var(--purple);
  background: var(--purple-soft);
  border: 1px solid #dbd0e3;
  border-radius: 999px;
  font-size: 0.78rem;
  font-weight: 650;
}

/* Evaluation */
.metric-block { padding: 3.1rem 0 1.4rem; border-top: 1px solid var(--line); }
.metric-block:first-of-type { margin-top: 3rem; }
.metric-block h3 { margin: 0 0 1.5rem; }
.metric-kicker {
  margin-bottom: 0.45rem;
  color: var(--purple-mid);
  font-size: 0.7rem;
  font-weight: 800;
  letter-spacing: 0.11em;
  text-transform: uppercase;
}
.equation {
  display: flex;
  align-items: center;
  gap: clamp(0.75rem, 2.5vw, 1.6rem);
  margin: 2rem 0;
  color: var(--purple-deep);
  font-family: "Cambria Math", "STIX Two Math", Georgia, serif;
  font-size: clamp(1.55rem, 4vw, 2.55rem);
  line-height: 1.1;
}
.math-variable { font-style: italic; }
.equation sub, .annotated-equation sub { font-size: 0.56em; }
.fraction {
  display: inline-grid;
  grid-template-rows: auto auto;
  text-align: center;
  font-size: 0.67em;
  line-height: 1.4;
}
.fraction > span:first-child { padding: 0 0.55rem 0.3rem; border-bottom: 1.5px solid currentColor; }
.fraction > span:last-child { padding-top: 0.28rem; }
.worked-example {
  display: flex;
  align-items: center;
  flex-wrap: wrap;
  gap: 0.65rem;
  margin: 1.5rem 0;
  color: var(--muted);
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.9rem;
}
.worked-example strong { color: var(--purple); }
.metric-direction, .lower-better {
  display: flex;
  align-items: center;
  gap: 0.5rem;
  color: var(--purple);
  font-weight: 750;
}
.metric-direction svg, .lower-better svg { width: 18px; height: 18px; }

.annotated-equation {
  display: flex;
  align-items: flex-end;
  flex-wrap: wrap;
  gap: clamp(0.75rem, 2vw, 1.35rem);
  margin: 2.4rem 0 2.2rem;
  color: var(--purple-deep);
  font-family: "Cambria Math", "STIX Two Math", Georgia, serif;
  font-size: clamp(2rem, 5vw, 3.6rem);
  line-height: 1;
}
.equation-result { padding-bottom: 0.05em; }
.equation-operator { padding-bottom: 0.05em; }
.annotated-term {
  display: inline-flex;
  flex-direction: column;
  align-items: center;
  gap: 0.45rem;
}
.annotated-term small {
  font-family: "Inter", sans-serif;
  font-size: 0.65rem;
  font-weight: 800;
  line-height: 1.2;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}
.annotated-term strong {
  position: relative;
  min-width: 1.5em;
  padding-top: 0.45rem;
  border-top: 2px solid currentColor;
  text-align: center;
}
.annotated-term strong::before,
.annotated-term strong::after {
  content: "";
  position: absolute;
  top: -2px;
  width: 7px;
  height: 6px;
  border-top: 2px solid currentColor;
}
.annotated-term strong::before { left: -2px; border-left: 2px solid currentColor; border-radius: 5px 0 0; }
.annotated-term strong::after { right: -2px; border-right: 2px solid currentColor; border-radius: 0 5px 0 0; }
.term-fertility { color: #70409a; }
.term-unknown { color: var(--yellow-deep); }
.table-compact { max-width: 520px; margin-bottom: 1rem; }
.table-compact td:last-child { font-variant-numeric: tabular-nums; }
.equation-final { margin-bottom: 1.8rem; }
.lower-better {
  width: fit-content;
  margin-top: 1.8rem;
  padding: 0.5rem 0.7rem;
  color: var(--purple-deep);
  background: var(--yellow);
  font-size: 0.77rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}

/* Leaderboard page */
.leaderboard-hero {
  padding: clamp(4.5rem, 8vw, 7rem) 0 clamp(3.5rem, 6vw, 5rem);
  background: var(--purple-soft);
  border-bottom: 1px solid var(--line);
}
.leaderboard-hero-inner { max-width: 960px; }
.leaderboard-hero h1 { margin-bottom: 1.2rem; }
.leaderboard-lead {
  max-width: 700px;
  margin: 0;
  color: var(--muted);
  font-size: clamp(1.08rem, 1.6vw, 1.25rem);
}
.back-link {
  display: inline-flex;
  align-items: center;
  gap: 0.45rem;
  margin-bottom: 3rem;
  font-size: 0.82rem;
  font-weight: 700;
}
.back-link svg { width: 16px; height: 16px; }
.leaderboard-page-section { padding: clamp(3.5rem, 7vw, 6rem) 0 clamp(5rem, 9vw, 8rem); }
.leaderboard-page-heading {
  display: flex;
  align-items: flex-end;
  justify-content: space-between;
  gap: 2rem;
}
.leaderboard-page-heading h2 { font-size: clamp(1.8rem, 3vw, 2.6rem); }
.leaderboard-page-heading p { margin: 0.4rem 0 0; color: var(--muted); }
.feed-notice {
  width: fit-content;
  display: flex;
  align-items: center;
  gap: 0.46rem;
  margin: 0;
  color: var(--muted);
  font-size: 0.68rem;
  font-weight: 800;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  white-space: nowrap;
}
.feed-notice span { width: 7px; height: 7px; border-radius: 50%; background: #2f8f5b; }
.leaderboard-table-wrap { margin: 0.8rem 0 0; background: var(--white); }
.leaderboard-table { min-width: 790px; }
.leaderboard-table th svg { width: 13px; height: 13px; margin-left: 0.2rem; vertical-align: -2px; }
.leaderboard-table td { height: 64px; white-space: nowrap; font-variant-numeric: tabular-nums; }
.leaderboard-table td:first-child { width: 68px; }
.leaderboard-table .rank-number {
  width: 28px;
  height: 28px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  border-radius: 50%;
  color: var(--muted);
  font-size: 0.78rem;
  font-weight: 800;
}
.leaderboard-table .rank-1 .rank-number { color: var(--purple-deep); background: var(--yellow); }
.leaderboard-table .rank-2 .rank-number { background: #e4e0e6; }
.leaderboard-table .rank-3 .rank-number { color: #744523; background: #edd7c7; }
.leaderboard-table .top-rank { background: #fffdf4; }
.leaderboard-table .score-value { color: var(--purple); }
.leaderboard-table a { display: inline-flex; align-items: center; gap: 0.3rem; font-weight: 650; }
.leaderboard-table a svg { width: 13px; height: 13px; }
.leaderboard-table .baseline-row { color: var(--muted); background: var(--purple-soft); }
.leaderboard-table .baseline-row .score-value { color: var(--muted); }
.baseline-tag {
  display: inline-block;
  margin-left: 0.4rem;
  padding: 0.14rem 0.42rem;
  border-radius: 999px;
  background: var(--white);
  border: 1px solid var(--line);
  color: var(--muted);
  font-size: 0.64rem;
  font-weight: 800;
  letter-spacing: 0.08em;
  text-transform: uppercase;
}
.leaderboard-table .reconstruction { font-variant-numeric: tabular-nums; }
.leaderboard-table .reconstruction-lossy {
  padding: 0.14rem 0.42rem;
  border-radius: 4px;
  color: #8a4b16;
  background: #fdeede;
  font-weight: 700;
}
.leaderboard-source-note { margin: 1.25rem 0 0; color: var(--muted); font-size: 0.84rem; }
.leaderboard-empty {
  margin: 0.8rem 0 0;
  padding: clamp(2.6rem, 6vw, 4.2rem) 1.5rem;
  display: grid;
  justify-items: center;
  gap: 0.55rem;
  text-align: center;
  background: var(--white);
  border: 1px dashed var(--line);
  border-radius: 14px;
}
.leaderboard-empty svg { width: 30px; height: 30px; color: var(--purple-mid); }
.leaderboard-empty h3 { margin: 0.35rem 0 0; font-size: 1.22rem; }
.leaderboard-empty p { max-width: 46ch; margin: 0; color: var(--muted); }
.leaderboard-empty .button { margin-top: 1rem; }

/* Submission */
.check-list { display: grid; gap: 0.55rem; margin: 1.2rem 0 3.6rem; list-style: none; }
.check-list li { position: relative; padding-left: 1.2rem; }
.check-list li::before {
  content: "";
  position: absolute;
  top: 0.72em;
  left: 0;
  width: 5px;
  height: 5px;
  border-radius: 50%;
  background: var(--purple);
}
.submission-steps { margin: 1.5rem 0 3.2rem; padding: 0; list-style: none; counter-reset: steps; }
.submission-steps li {
  display: grid;
  grid-template-columns: 38px minmax(0, 1fr);
  gap: 1rem;
  padding: 1.15rem 0;
  border-top: 1px solid var(--line);
}
.submission-steps li:last-child { border-bottom: 1px solid var(--line); }
.submission-steps li > span {
  width: 30px;
  height: 30px;
  display: inline-flex;
  align-items: center;
  justify-content: center;
  margin-top: 0.1rem;
  color: var(--purple);
  background: var(--yellow);
  border-radius: 50%;
  font-size: 0.75rem;
  font-weight: 800;
}
.submission-steps strong { display: block; color: var(--purple-deep); }
.submission-steps p { margin: 0.18rem 0 0; color: var(--muted); }
.automation-note {
  display: grid;
  grid-template-columns: 32px minmax(0, 1fr);
  gap: 1rem;
  margin: 0 0 2.2rem;
  padding: 1.3rem 0;
  border-top: 3px solid var(--yellow);
  border-bottom: 1px solid var(--line);
}
.automation-note > svg { width: 24px; height: 24px; color: var(--purple); }
.automation-note h3 { margin: 0 0 0.35rem; }
.automation-note p { margin: 0; }

.starter-notebook {
  display: grid;
  grid-template-columns: 34px minmax(0, 1fr);
  gap: 1rem;
  margin: 0 0 3.5rem;
  padding: 1.5rem 0;
  border-top: 3px solid var(--purple);
  border-bottom: 1px solid var(--line);
}
.starter-notebook > svg {
  width: 25px;
  height: 25px;
  margin-top: 0.15rem;
  color: var(--purple);
}
.starter-notebook .starter-notebook-label {
  margin: 0 0 0.35rem;
  color: var(--purple-mid);
  font-size: 0.68rem;
  font-weight: 800;
  letter-spacing: 0.11em;
  text-transform: uppercase;
}
.starter-notebook h3 { margin: 0 0 0.6rem; }
.starter-notebook p { margin-bottom: 0.85rem; }
.starter-notebook .text-link { font-size: 0.88rem; }

/* FAQ */
.faq-list details { border-top: 1px solid var(--line); }
.faq-list details:last-child { border-bottom: 1px solid var(--line); }
.faq-list summary {
  position: relative;
  padding: 1.3rem 3rem 1.3rem 0;
  color: var(--purple-deep);
  font-weight: 700;
  line-height: 1.45;
  list-style: none;
  cursor: pointer;
}
.faq-list summary::-webkit-details-marker { display: none; }
.faq-list summary::after {
  content: "+";
  position: absolute;
  top: 1.05rem;
  right: 0;
  color: var(--purple);
  font-size: 1.55rem;
  font-weight: 400;
}
.faq-list details[open] summary::after { content: "−"; }
.faq-list details p { max-width: 680px; padding: 0 2rem 1.3rem 0; color: var(--muted); }

/* Learning and footer */
.learning-section {
  padding-top: clamp(4.5rem, 8vw, 7rem);
  padding-bottom: clamp(4.5rem, 8vw, 7rem);
  color: rgba(255, 255, 255, 0.8);
  background: var(--purple);
  box-shadow: 0 0 0 100vmax var(--purple);
  clip-path: inset(0 -100vmax);
}
.learning-section .eyebrow { color: var(--yellow); }
.learning-section h2, .learning-section h3 { color: var(--white); }
.learning-layout { display: grid; grid-template-columns: 0.8fr 1.2fr; gap: clamp(3rem, 8vw, 7rem); }
.course-list > div { padding: 1.2rem 0 1.5rem; border-top: 1px solid rgba(255, 255, 255, 0.24); }
.course-list > div:last-child { border-bottom: 1px solid rgba(255, 255, 255, 0.24); }
.course-list span { color: var(--yellow); font-size: 0.7rem; font-weight: 800; letter-spacing: 0.1em; text-transform: uppercase; }
.course-list h3 { margin: 0.45rem 0 0.65rem; }
.course-list p { margin: 0; }
.text-link-light { margin-top: 2rem; color: var(--white); }

.site-footer { color: rgba(255, 255, 255, 0.66); background: var(--purple-deep); }
.footer-inner {
  min-height: 170px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 2rem;
  padding-top: 2rem;
  padding-bottom: 2rem;
}
.footer-inner p { margin: 0; font-size: 0.86rem; }
.footer-inner .footer-title { margin-bottom: 0.15rem; color: var(--white); font-weight: 750; }
.footer-links { display: flex; flex-wrap: wrap; gap: 1.6rem; }
.footer-links a { color: var(--white); font-size: 0.84rem; font-weight: 650; }

/* Fallback styling for legacy content routes */
.container { width: min(100% - 48px, var(--max-width)); margin-inline: auto; }
.prose { max-width: var(--content-width); margin: 4rem auto; }

/* Tool calling hackathon: stacked hero banner, tool-call example and code blocks */
.hero-layout.hero-stacked { grid-template-columns: minmax(0, 1fr); gap: clamp(2.5rem, 5vw, 3.75rem); }
.hero-stacked .hero-copy h1 { max-width: 960px; }
.hero-stacked .hero-lead { max-width: 720px; }
.hero-banner { min-width: 0; margin: 0; }
.hero-banner a { display: block; }
.hero-banner img {
  display: block;
  width: 100%;
  height: auto;
  border: 1px solid var(--line);
  border-radius: 8px;
  box-shadow: 0 22px 60px rgba(54, 26, 84, 0.12);
}

.tool-example {
  margin: 2.2rem 0;
  padding: 1.5rem 1.5rem 0.4rem;
  background: var(--white);
  border: 1px solid var(--line);
  border-top: 3px solid var(--purple);
}
.tool-example .tool-example-label {
  margin: 0 0 0.55rem;
  color: var(--purple-mid);
  font-size: 0.68rem;
  font-weight: 800;
  letter-spacing: 0.11em;
  text-transform: uppercase;
}
.tool-example-request {
  margin: 0 0 1.5rem;
  color: var(--purple-deep);
  font-size: 1.15rem;
  font-weight: 650;
}
.tool-chips {
  display: flex;
  flex-wrap: wrap;
  gap: 0.45rem;
  margin: 0 0 1.5rem;
  padding: 0 !important;
  list-style: none;
}
.tool-chips code {
  display: inline-block;
  padding: 0.35rem 0.65rem;
  color: var(--muted);
  background: var(--paper);
  border: 1px solid var(--line);
  border-radius: 5px;
}
.tool-chips .is-answer code {
  color: var(--purple);
  background: var(--yellow-soft);
  border-color: var(--yellow);
  font-weight: 700;
}
.code-block {
  margin: 0 0 2.2rem;
  padding: 1.15rem 1.3rem;
  overflow-x: auto;
  color: #f4f0f7;
  background: var(--purple-deep);
  border-radius: 6px;
  font-family: ui-monospace, SFMono-Regular, Menlo, Consolas, monospace;
  font-size: 0.84rem;
  line-height: 1.6;
}
.tool-example .code-block { margin-bottom: 1.1rem; }
.code-block code { padding: 0; color: inherit; background: none; font-size: inherit; }

.cross-list { display: grid; gap: 0.55rem; margin: 1.2rem 0 2.4rem; list-style: none; }
.cross-list li { position: relative; padding-left: 1.4rem; }
.cross-list li::before {
  content: "\00d7";
  position: absolute;
  top: 0;
  left: 0;
  color: #b3261e;
  font-weight: 800;
}
.link-row { display: flex; flex-wrap: wrap; gap: 0.6rem 1.6rem; }

@media (max-width: 960px) {
  .hero-layout { grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 2rem; }
  .doc-section { grid-template-columns: minmax(150px, 195px) minmax(0, 1fr); gap: 3rem; }
}

@media (max-width: 760px) {
  :root { --header-height: 66px; --section-nav-height: 52px; }
  body { font-size: 16px; }
  .wide-container, .container { width: min(100% - 32px, var(--max-width)); }
  .header-inner { min-height: var(--header-height); }
  .challenge-brand span { font-size: 0.58rem; }
  .challenge-brand strong { font-size: 0.89rem; }
  .nav-toggle { display: inline-flex; }
  .primary-nav {
    position: absolute;
    top: 100%;
    right: 0;
    left: 0;
    display: none;
    flex-direction: column;
    align-items: stretch;
    gap: 0;
    padding: 0.5rem 1rem 1rem;
    background: var(--purple);
    border-bottom: 1px solid rgba(255, 255, 255, 0.18);
  }
  .primary-nav.open { display: flex; }
  .primary-nav a { padding: 0.8rem; }
  .primary-nav .github-link { margin-top: 0.3rem; justify-content: center; }
  .challenge-hero { padding-top: 4rem; }
  .hero-layout { grid-template-columns: 1fr; }
  .hero-art { margin-top: 1.2rem; }
  .hero-art img { width: min(100%, 620px); max-width: 100%; max-height: none; }
  .section-nav-scroll { gap: 1.4rem; }
  .doc-section {
    display: block;
    padding-top: 5rem;
    padding-bottom: 5rem;
  }
  .section-heading { margin-bottom: 2.5rem; }
  .section-number { margin-top: 0.25rem; }
  .section-heading h2 { font-size: 2.5rem; }
  .learning-layout { grid-template-columns: 1fr; gap: 2.5rem; }
}

@media (max-width: 560px) {
  h1 { font-size: clamp(2.4rem, 12vw, 3.35rem); }
  .button-row { align-items: stretch; }
  .button { flex: 1 1 auto; }
  .section-nav a { font-size: 0.92rem; }
  .baseline-list { grid-template-columns: 1fr; gap: 1.5rem; }
  .skills-list { grid-template-columns: 1fr; gap: 0; }
  .skills-list li:nth-last-child(2):nth-child(odd) { border-bottom: 0; }
  .skills-list li:last-child { border-bottom: 1px solid var(--line); }
  .split-list dt span { display: block; float: none; margin-top: 0.1rem; }
  .equation { font-size: 1.48rem; gap: 0.6rem; }
  .equation .fraction { font-size: 0.63em; }
  .annotated-equation { align-items: flex-end; font-size: 2rem; gap: 0.65rem; }
  .annotated-term small { max-width: 100px; text-align: center; font-size: 0.53rem; }
  .footer-inner { min-height: 190px; flex-direction: column; align-items: flex-start; justify-content: center; }
  .leaderboard-page-heading { align-items: flex-start; flex-direction: column; gap: 1.2rem; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { transition-duration: 0.01ms !important; }
}

@media print {
  .site-header, .section-nav, .site-footer, .button-row { display: none; }
  body { color: #000; background: #fff; }
  .challenge-hero { padding: 2rem 0; }
  .doc-section { display: block; padding: 2.5rem 0; break-inside: avoid; }
  .section-heading { margin-bottom: 1.5rem; }
  .learning-section, .leaderboard-hero { color: #000; background: #fff; box-shadow: none; }
  .learning-section h2, .learning-section h3 { color: #000; }
}