/* Hallmark · editorial · Long Document · existing green course palette */
:root { color-scheme: light; --ink: #17231d; --muted: #59665f; --paper: #fbfcfa; --soft: #f1f5f1; --line: #ced8d0; --blue: #176f91; --accent: #176f91; --font-body: ui-sans-serif, system-ui, -apple-system, "Noto Sans CJK SC", sans-serif; --font-display: Charter, "Bitstream Charter", Georgia, serif; --font-code: ui-monospace, SFMono-Regular, Menlo, monospace; }
* { box-sizing: border-box; }
body { margin: 0; background: var(--paper); color: var(--ink); font-family: var(--font-body); line-height: 1.85; }
a { color: var(--blue); text-underline-offset: 3px; }
.shell { width: min(1260px, calc(100% - 40px)); margin-inline: auto; }
header { position: sticky; top: 0; background: var(--paper); z-index: 10; border-bottom: 1px solid var(--line); }
header .shell { display: flex; min-height: 64px; align-items: center; justify-content: space-between; gap: 24px; }
.brand { color: var(--ink); text-decoration: none; font-weight: 750; }
nav { display: flex; gap: 24px; font-size: .9rem; }
nav a { text-decoration: none; }
.reading-layout { display: grid; grid-template-columns: 220px minmax(0, 1fr); gap: 56px; padding-block: 48px 80px; }
aside { position: sticky; top: 96px; align-self: start; max-height: calc(100svh - 120px); overflow-y: auto; font-size: .85rem; }
aside summary { color: var(--muted); margin-bottom: 12px; }
aside a { display: block; padding: 7px 0; text-decoration: none; line-height: 1.5; }
main { min-width: 0; }
main > p, main > ul, main > ol { max-width: 76ch; }
.article-context { margin-top: 0; font-size: .9rem; }
.clip { margin: 28px 0; }
.clip video { display: block; width: 100%; height: auto; background: var(--ink); }
.clip figcaption { margin-top: 10px; color: var(--muted); font-size: .9rem; }
main details { margin-block: 20px; padding: 16px 20px; background: var(--soft); border-inline-start: 3px solid var(--line); }
main summary { cursor: pointer; color: var(--blue); }
main details > :last-child { margin-bottom: 0; }
.lesson-nav { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 16px; border-top: 1px solid var(--line); margin-top: 48px; padding-top: 24px; }
.lesson-nav a { min-height: 44px; display: inline-flex; align-items: center; white-space: nowrap; }
.signal-flow { display: flex; flex-wrap: wrap; gap: 12px; align-items: center; padding: 20px; margin-block: 24px; background: var(--soft); }
.signal-flow span { min-width: 0; }
h1,h2,h3,h4 { font-family: var(--font-display); line-height: 1.3; }
h1 { margin-top: 0; font-size: clamp(2rem, 3.5vw, 3rem); }
h2 { border-top: 1px solid var(--line); margin-top: 48px; padding-top: 24px; font-size: 1.65rem; }
h3 { margin-top: 36px; font-size: 1.3rem; }
p,li { overflow-wrap: anywhere; }
pre { padding: 20px; background: var(--soft); overflow-x: auto; border: 1px solid var(--line); line-height: 1.6; }
code { font: .88em var(--font-code); }
blockquote { margin-inline: 0; padding: 4px 24px; border-left: 3px solid var(--blue); color: var(--muted); }
img { max-width: 100%; height: auto; }
.table-scroll { max-width: 100%; overflow-x: auto; margin-block: 24px; }
table { width: 100%; border-collapse: collapse; font-size: .9rem; }
th,td { text-align: start; padding: 12px; border-bottom: 1px solid var(--line); min-width: 110px; vertical-align: top; }
th { background: var(--soft); }
footer { border-top: 1px solid var(--line); padding-block: 24px 40px; display: flex; flex-wrap: wrap; justify-content: space-between; gap: 16px; font-size: .9rem; }
.katex-display { overflow-x: auto; overflow-y: clip; padding-block: 8px; }
@media(max-width: 900px) { .reading-layout { grid-template-columns: minmax(0, 1fr); gap: 20px; padding-top: 24px; } aside { position: static; max-height: 160px; } aside details { border-bottom: 1px solid var(--line); padding-bottom: 12px; } aside a { display: inline-block; margin-right: 20px; } }
@media(max-width: 420px) { .shell { width: calc(100% - 24px); } body { font-size: 15px; } th,td { padding: 8px; } }

/* L0 reading treatment: carry the reference's paper, evidence, and boundary language into the document flow. */
.lesson-l0 main { max-width: 860px; }
.lesson-l0 .lesson-eyebrow { margin: 0 0 12px; color: var(--page-accent); font: 700 .78rem/1.35 var(--font-code); letter-spacing: .08em; text-transform: uppercase; }
.lesson-l0 .lesson-lede { max-width: 58ch; margin-top: 0; color: var(--ink); font-size: 1.28rem; line-height: 1.6; }
.lesson-l0 .lesson-context { max-width: 68ch; color: var(--muted); }
.lesson-l0 .experiment-contract { margin: 2rem 0 3rem; padding: 1.2rem; border: 1px solid color-mix(in srgb, var(--page-accent) 28%, var(--line)); border-top: 4px solid var(--page-accent); background: var(--surface); box-shadow: var(--shadow-soft); }
.lesson-l0 .contract-label { margin: 0 0 1rem; color: var(--page-accent); font: 700 .76rem/1.35 var(--font-code); letter-spacing: .08em; text-transform: uppercase; }
.lesson-l0 .contract-flow { display: flex; align-items: stretch; gap: .55rem; }
.lesson-l0 .contract-step { flex: 1 1 0; min-width: 0; padding: .85rem .9rem; border: 1px solid var(--line); background: var(--paper); }
.lesson-l0 .contract-step strong { display: block; margin-bottom: .25rem; font-size: .95rem; }
.lesson-l0 .contract-step span { display: block; color: var(--muted); font-size: .85rem; line-height: 1.45; }
.lesson-l0 .contract-arrow { display: grid; place-items: center; flex: none; color: var(--page-accent); font-size: 1.25rem; }
.lesson-l0 h2::before { content: ""; display: block; width: 3.5rem; height: 3px; margin-bottom: .9rem; background: var(--page-accent); }
.lesson-l0 .clip, .lesson-l0 .report-figure { margin: 2.3rem 0; padding: 1rem; border: 1px solid var(--line); border-top: 3px solid var(--page-accent); background: var(--surface); box-shadow: var(--shadow-soft); }
.lesson-l0 .clip figcaption, .lesson-l0 .report-figure figcaption { margin-top: .8rem; color: var(--ink); font-size: .9rem; font-weight: 650; }
.lesson-l0 .clip figcaption::before { content: "Evidence / "; color: var(--page-accent); font: 700 .74rem/1.35 var(--font-code); letter-spacing: .05em; text-transform: uppercase; }
.lesson-l0 .clip details { margin: 1rem 0 0; border-inline-start-color: var(--page-accent); }
.lesson-l0 .report-figure { text-align: left; }
.lesson-l0 .report-figure img { display: block; width: 100%; border: 1px solid var(--line); }
.lesson-l0 .table-scroll { margin-block: 1.8rem; padding: .3rem; border: 1px solid var(--line); background: var(--surface); box-shadow: var(--shadow-soft); }
.lesson-l0 .table-scroll table { margin: 0; }
.lesson-l0 .table-scroll th { color: var(--page-accent); font: 700 .76rem/1.35 var(--font-code); letter-spacing: .03em; }
.lesson-l0 .evidence-callout { margin: 2rem 0; padding: 1.2rem 1.3rem; border: 1px solid color-mix(in srgb, var(--page-accent) 28%, var(--line)); border-inline-start: 4px solid var(--page-accent); background: var(--page-soft); }
.lesson-l0 .evidence-callout strong { display: block; margin-bottom: .35rem; color: var(--page-accent); font: 700 .78rem/1.35 var(--font-code); letter-spacing: .08em; text-transform: uppercase; }
.lesson-l0 .evidence-callout p { margin: 0; max-width: 68ch; }
.lesson-l0 #limits + p { margin-top: 1.8rem; padding: 1.2rem 1.3rem .7rem; border: 1px solid var(--line); border-bottom: 0; background: var(--page-soft); }
.lesson-l0 #limits + p + p { margin-top: 0; padding: .7rem 1.3rem 1.2rem; border: 1px solid var(--line); border-top: 0; background: var(--page-soft); }
@media(max-width: 700px) {
  .lesson-l0 .lesson-lede { font-size: 1.12rem; }
  .lesson-l0 .experiment-contract { margin-block: 1.6rem 2.4rem; padding: 1rem; }
  .lesson-l0 .contract-flow { display: grid; grid-template-columns: minmax(0, 1fr); gap: .45rem; }
  .lesson-l0 .contract-arrow { min-height: 1rem; transform: rotate(90deg); }
  .lesson-l0 .clip, .lesson-l0 .report-figure { margin-block: 1.8rem; padding: .65rem; }
}