:root {
  --learn-ink: #171916;
  --learn-paper: #f3f0e7;
  --learn-deep: #e7e2d5;
  --learn-line: #b9b5aa;
  --learn-blue: #195f91;
  --learn-orange: #c4512e;
  --learn-green: #3f704f;
  --learn-violet: #66558a;
}

* { box-sizing: border-box; }

.learn-body {
  margin: 0;
  color: var(--learn-ink);
  background: #d9d4c8;
  font-family: Arial, Helvetica, sans-serif;
}

.learn-masthead {
  position: sticky;
  top: 0;
  z-index: 40;
  min-height: 58px;
  display: flex;
  align-items: stretch;
  justify-content: space-between;
  border-bottom: 1px solid var(--learn-ink);
  background: rgba(243, 240, 231, .96);
  backdrop-filter: blur(12px);
}

.learn-brand {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 0 22px;
  color: inherit;
  text-decoration: none;
  font: 700 11px/1 var(--mono, monospace);
  letter-spacing: .07em;
  text-transform: uppercase;
}

.learn-brand span {
  display: grid;
  place-items: center;
  width: 35px;
  height: 24px;
  color: var(--learn-paper);
  background: var(--learn-ink);
  font-size: 9px;
}

.learn-masthead nav { display: flex; }
.learn-masthead nav a {
  display: grid;
  place-items: center;
  min-width: 90px;
  padding: 0 16px;
  border-left: 1px solid var(--learn-line);
  color: inherit;
  text-decoration: none;
  font: 700 9px/1 var(--mono, monospace);
  letter-spacing: .08em;
  text-transform: uppercase;
}
.learn-masthead nav a:hover,
.learn-masthead nav a:focus-visible,
.learn-masthead nav a[aria-current="page"] { background: var(--learn-ink); color: var(--learn-paper); }

.curriculum-page,
.lesson-page,
.field-note-page {
  width: min(1380px, calc(100vw - 32px));
  margin: 16px auto 54px;
  background: var(--learn-paper);
  box-shadow: 9px 11px 0 rgba(23, 25, 22, .08);
}

.curriculum-hero {
  min-height: 640px;
  padding: clamp(54px, 8vw, 115px);
  display: grid;
  align-content: space-between;
  border-bottom: 1px solid var(--learn-ink);
}
.lesson-eyebrow {
  margin: 0 0 24px;
  color: var(--learn-orange);
  font: 700 10px/1.2 var(--mono, monospace);
  letter-spacing: .12em;
  text-transform: uppercase;
}
.curriculum-hero h1,
.lesson-hero h1 {
  max-width: 980px;
  margin: 0;
  font: 400 clamp(62px, 9vw, 132px)/.82 Georgia, serif;
  letter-spacing: -.065em;
}
.curriculum-hero > div > p:last-child {
  max-width: 690px;
  margin: 34px 0 0;
  font: 400 clamp(17px, 2vw, 24px)/1.45 Georgia, serif;
}
.learning-loop {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding-top: 28px;
  border-top: 1px solid var(--learn-ink);
  font: 700 10px/1 var(--mono, monospace);
  letter-spacing: .08em;
  text-transform: uppercase;
}
.learning-loop span { padding: 9px 12px; border: 1px solid var(--learn-ink); }
.learning-loop i { font-style: normal; }

.curriculum-list,
.field-notes { padding: clamp(32px, 6vw, 82px); border-bottom: 1px solid var(--learn-ink); }
.curriculum-heading {
  display: grid;
  grid-template-columns: 150px 1fr auto;
  align-items: baseline;
  gap: 20px;
  margin-bottom: 34px;
}
.curriculum-heading > span {
  font: 700 9px/1 var(--mono, monospace);
  letter-spacing: .1em;
  text-transform: uppercase;
}
.curriculum-heading h2,
.section-heading h2 {
  margin: 0;
  font: 400 clamp(32px, 5vw, 64px)/.95 Georgia, serif;
  letter-spacing: -.045em;
}
.curriculum-heading button {
  border: 0;
  border-bottom: 1px solid;
  background: transparent;
  font: 700 9px/1.8 var(--mono, monospace);
  text-transform: uppercase;
  cursor: pointer;
}
.curriculum-row {
  min-height: 112px;
  display: grid;
  grid-template-columns: 150px minmax(0, 1fr) 140px;
  align-items: center;
  gap: 20px;
  border-top: 1px solid var(--learn-ink);
  color: inherit;
  text-decoration: none;
}
.curriculum-row:last-child { border-bottom: 1px solid var(--learn-ink); }
.curriculum-row:hover,
.curriculum-row:focus-visible { padding-left: 14px; background: var(--learn-deep); }
.curriculum-number { font: 400 42px/1 Georgia, serif; }
.curriculum-row b { display: block; font: 400 clamp(22px, 3vw, 36px)/1 Georgia, serif; }
.curriculum-row small { display: block; margin-top: 8px; color: #62635e; font-size: 13px; }
.curriculum-state { text-align: right; font: 700 9px/1.4 var(--mono, monospace); text-transform: uppercase; }
.curriculum-row.completed .curriculum-state { color: var(--learn-green); }

.field-note-grid { display: grid; grid-template-columns: repeat(3, 1fr); border: 1px solid var(--learn-ink); }
.field-note-link { min-height: 240px; padding: 24px; color: inherit; text-decoration: none; border-right: 1px solid var(--learn-ink); }
.field-note-link:last-child { border-right: 0; }
.field-note-link:hover, .field-note-link:focus-visible { background: var(--learn-ink); color: var(--learn-paper); }
.field-note-link span, .field-note-link small { display: block; }
.field-note-link span { font: 700 9px/1 var(--mono, monospace); text-transform: uppercase; }
.field-note-link b { display: block; margin: 48px 0 15px; font: 400 34px/1 Georgia, serif; }
.field-note-link small { line-height: 1.5; }
.curriculum-page > .provenance { margin: 0; border: 0; }

.lesson-page { display: grid; grid-template-columns: 210px minmax(0, 1fr); }
.lesson-rail {
  position: sticky;
  top: 58px;
  height: calc(100vh - 74px);
  padding: 28px 22px;
  display: flex;
  flex-direction: column;
  border-right: 1px solid var(--learn-ink);
  font: 700 9px/1.4 var(--mono, monospace);
  letter-spacing: .08em;
  text-transform: uppercase;
}
.lesson-rail a { color: inherit; }
.lesson-rail > span { margin-top: auto; }
.rail-progress { height: 4px; margin-top: 12px; background: var(--learn-line); }
.rail-progress i { display: block; width: var(--progress); height: 100%; background: var(--learn-orange); }
.lesson-article { min-width: 0; }
.lesson-hero {
  min-height: 710px;
  padding: clamp(42px, 7vw, 92px);
  display: grid;
  align-content: space-between;
  border-bottom: 1px solid var(--learn-ink);
}
.lesson-hero h1 { max-width: 900px; font-size: clamp(60px, 8vw, 112px); }
.lesson-lede { max-width: 700px; margin: 32px 0 0; font: 400 22px/1.45 Georgia, serif; }
.provenance {
  margin-top: 45px;
  padding: 14px 0;
  display: grid;
  grid-template-columns: 130px 1fr auto;
  gap: 18px;
  border-top: 1px solid var(--learn-ink);
  border-bottom: 1px solid var(--learn-ink);
  font: 700 9px/1.3 var(--mono, monospace);
  text-transform: uppercase;
}
.provenance a { color: inherit; overflow-wrap: anywhere; }
.provenance code { color: var(--learn-orange); }

.lesson-section { padding: clamp(38px, 6vw, 80px); border-bottom: 1px solid var(--learn-ink); }
.section-heading { display: grid; grid-template-columns: 150px minmax(0, 1fr); gap: 20px; margin-bottom: 46px; }
.section-heading > span { font: 700 9px/1.2 var(--mono, monospace); letter-spacing: .1em; text-transform: uppercase; }
.boundary-pair { display: grid; grid-template-columns: 1fr 1fr; border: 1px solid var(--learn-ink); }
.boundary-pair > div { min-height: 230px; padding: 25px; }
.boundary-pair > div:first-child { border-right: 1px solid var(--learn-ink); }
.boundary-pair b { color: var(--learn-orange); font: 700 9px/1 var(--mono, monospace); text-transform: uppercase; }
.boundary-pair p { margin: 38px 0 0; font: 400 19px/1.5 Georgia, serif; }

.lesson-shape {
  min-height: 260px;
  padding: 28px;
  display: flex;
  align-items: center;
  justify-content: center;
  gap: 13px;
  overflow-x: auto;
  border: 1px solid var(--learn-ink);
  background-image: linear-gradient(var(--learn-line) 1px, transparent 1px), linear-gradient(90deg, var(--learn-line) 1px, transparent 1px);
  background-size: 24px 24px;
}
.shape-node {
  flex: 0 0 135px;
  min-height: 80px;
  padding: 12px;
  border: 1px solid var(--learn-ink);
  background: var(--learn-paper);
  color: inherit;
  cursor: pointer;
}
.shape-node.active { outline: 4px solid rgba(25,95,145,.22); transform: translateY(-3px); }
.shape-node span, .shape-node small { display: block; }
.shape-node span { font-weight: 700; }
.shape-node small { margin-top: 8px; font: 700 8px/1 var(--mono, monospace); text-transform: uppercase; }
.shape-node.transform { border-top: 5px solid var(--learn-blue); }
.shape-node.trace, .shape-node.state { border-top: 5px solid var(--learn-violet); }
.shape-node.evaluation { border-top: 5px solid var(--learn-orange); }
.shape-node.feedback { border-top: 5px solid var(--learn-green); }
.shape-arrow { font: 700 20px/1 var(--mono, monospace); }
.inspectable-note { margin: 22px 0 0; font: 400 16px/1.55 Georgia, serif; }

.lesson-lab { display: grid; grid-template-columns: 240px minmax(0, 1fr); border: 1px solid var(--learn-ink); }
.lab-controls { padding: 20px; border-right: 1px solid var(--learn-ink); }
.lab-controls label { display: block; margin-bottom: 20px; font: 700 9px/1.4 var(--mono, monospace); text-transform: uppercase; }
.lab-controls input[type="range"] { width: 100%; margin-top: 12px; accent-color: var(--learn-orange); }
.lab-controls input[type="text"] { width: 100%; margin-top: 10px; padding: 10px; border: 1px solid var(--learn-ink); background: white; }
.lab-controls button, .lesson-button {
  min-height: 40px;
  padding: 0 15px;
  border: 1px solid var(--learn-ink);
  background: var(--learn-ink);
  color: var(--learn-paper);
  font: 700 9px/1 var(--mono, monospace);
  letter-spacing: .06em;
  text-transform: uppercase;
  cursor: pointer;
}
.lab-output { min-width: 0; padding: 20px; }
.lab-status { margin: 0 0 18px; color: #555750; font: 700 9px/1.4 var(--mono, monospace); text-transform: uppercase; }
.trace-table { border: 1px solid var(--learn-ink); }
.trace-row {
  width: 100%;
  display: grid;
  grid-template-columns: 160px minmax(0, 1fr) minmax(0, 1fr);
  gap: 12px;
  padding: 13px;
  border: 0;
  border-bottom: 1px solid var(--learn-line);
  background: transparent;
  color: inherit;
  text-align: left;
  cursor: pointer;
}
.trace-row:last-child { border-bottom: 0; }
.trace-row.active { background: #e1dcd0; box-shadow: inset 4px 0 var(--learn-blue); }
.trace-row b { font: 700 10px/1.4 var(--mono, monospace); }
.trace-row span, .trace-row strong { overflow-wrap: anywhere; font: 400 12px/1.4 var(--mono, monospace); }
.trace-row strong { color: var(--learn-blue); }

.code-workbench { border: 1px solid var(--learn-ink); background: #171916; color: #ece9df; }
.code-toolbar { height: 50px; display: flex; border-bottom: 1px solid #565850; }
.code-toolbar button {
  padding: 0 18px;
  border: 0;
  border-right: 1px solid #565850;
  background: transparent;
  color: inherit;
  font: 700 9px/1 var(--mono, monospace);
  text-transform: uppercase;
  cursor: pointer;
}
.code-toolbar button[aria-selected="true"] { background: var(--learn-paper); color: var(--learn-ink); }
.code-toolbar .copy-control { margin-left: auto; border-left: 1px solid #565850; border-right: 0; }
.code-workbench pre { min-height: 330px; margin: 0; padding: 28px; overflow: auto; font: 400 13px/1.7 var(--mono, monospace); }
.code-workbench pre[hidden] { display: none; }

.interpretation-section { background: #282b26; color: var(--learn-paper); }
.interpretation-section p { max-width: 780px; margin: 0 0 0 170px; font: 400 clamp(22px, 3vw, 38px)/1.25 Georgia, serif; }
.quiz-options { display: grid; border: 1px solid var(--learn-ink); margin-bottom: 22px; }
.quiz-options label { padding: 18px; border-bottom: 1px solid var(--learn-line); cursor: pointer; }
.quiz-options label:last-child { border-bottom: 0; }
.quiz-options input { accent-color: var(--learn-orange); }
.quiz-result { min-height: 48px; margin: 18px 0 0; font: 700 12px/1.5 var(--mono, monospace); }
.quiz-result.correct { color: var(--learn-green); }
.quiz-result.incorrect { color: var(--learn-orange); }

.lesson-pagination { display: grid; grid-template-columns: 1fr 1fr; }
.lesson-pagination a { min-height: 140px; padding: 28px; color: inherit; text-decoration: none; font: 400 24px/1.15 Georgia, serif; }
.lesson-pagination a:first-child { border-right: 1px solid var(--learn-ink); }
.lesson-pagination a:hover, .lesson-pagination a:focus-visible { background: var(--learn-deep); }
.lesson-pagination a span { display: block; margin-bottom: 20px; font: 700 9px/1 var(--mono, monospace); text-transform: uppercase; }
.lesson-pagination .next { text-align: right; }

.field-note-page { padding: clamp(32px, 6vw, 82px); }
.back-link { color: inherit; font: 700 9px/1 var(--mono, monospace); text-transform: uppercase; }
.field-note-page .lesson-hero { min-height: 620px; padding-left: 0; padding-right: 0; }
.note-register { border: 1px solid var(--learn-ink); }
.note-register section { min-height: 210px; display: grid; grid-template-columns: 70px 1fr 1fr; gap: 25px; padding: 28px; border-bottom: 1px solid var(--learn-ink); }
.note-register section:last-child { border-bottom: 0; }
.note-register span { font: 700 10px/1 var(--mono, monospace); }
.note-register h2 { margin: 0; font: 400 35px/1 Georgia, serif; }
.note-register p { margin: 0; line-height: 1.55; }
.field-note-boundary { margin-top: 28px; padding: 32px; }
.field-note-boundary p { margin: 18px 0 0; font-size: 22px; }

:focus-visible { outline: 3px solid var(--learn-orange); outline-offset: 3px; }

@media (max-width: 760px) {
  .learn-masthead { position: static; display: block; }
  .learn-brand { min-height: 52px; }
  .learn-masthead nav { overflow-x: auto; border-top: 1px solid var(--learn-ink); }
  .learn-masthead nav a { min-width: 94px; min-height: 42px; }
  .curriculum-page, .lesson-page, .field-note-page { width: calc(100vw - 16px); margin: 8px auto 28px; }
  .curriculum-hero { min-height: 610px; padding: 38px 20px; }
  .curriculum-hero h1, .lesson-hero h1 { font-size: clamp(54px, 18vw, 76px); }
  .learning-loop { flex-wrap: wrap; justify-content: flex-start; }
  .learning-loop i { display: none; }
  .curriculum-list, .field-notes, .lesson-section, .field-note-page { padding: 42px 20px; }
  .curriculum-heading { grid-template-columns: 1fr; }
  .curriculum-row { min-height: 145px; grid-template-columns: 54px minmax(0, 1fr); gap: 12px; }
  .curriculum-state { grid-column: 2; text-align: left; }
  .field-note-grid { grid-template-columns: 1fr; }
  .field-note-link { border-right: 0; border-bottom: 1px solid var(--learn-ink); }
  .field-note-link:last-child { border-bottom: 0; }
  .lesson-page { display: block; }
  .lesson-rail { position: static; width: 100%; height: auto; flex-direction: row; align-items: center; gap: 14px; border-right: 0; border-bottom: 1px solid var(--learn-ink); }
  .lesson-rail > span { margin: 0 0 0 auto; }
  .rail-progress { width: 60px; margin: 0; }
  .lesson-hero { min-height: 650px; padding: 48px 20px; }
  .provenance { grid-template-columns: 1fr; }
  .section-heading { grid-template-columns: 1fr; }
  .boundary-pair, .lesson-lab { grid-template-columns: 1fr; }
  .boundary-pair > div:first-child { border-right: 0; border-bottom: 1px solid var(--learn-ink); }
  .lesson-shape { justify-content: flex-start; }
  .lab-controls { border-right: 0; border-bottom: 1px solid var(--learn-ink); }
  .trace-row { grid-template-columns: 1fr; }
  .interpretation-section p { margin-left: 0; }
  .code-workbench pre { min-height: 280px; font-size: 11px; }
  .lesson-pagination { grid-template-columns: 1fr; }
  .lesson-pagination a:first-child { border-right: 0; border-bottom: 1px solid var(--learn-ink); }
  .note-register section { grid-template-columns: 42px 1fr; }
  .note-register p { grid-column: 2; }
}

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { scroll-behavior: auto !important; transition: none !important; animation: none !important; }
  .shape-node.active { transform: none; }
}