/* Canonical lesson stylesheet. Copy byte-for-byte to every subject assets/course.css. */
@font-face {
  font-family: "Archivo Variable";
  font-style: normal;
  font-weight: 100 900;
  font-display: swap;
  src: url("/fonts/archivo-latin-wght-normal.woff2") format("woff2-variations");
}

@font-face {
  font-family: "Inter Variable";
  font-style: normal;
  font-weight: 100 900;
  font-display: swap;
  src: url("/fonts/inter-latin-wght-normal.woff2") format("woff2-variations");
}

@font-face {
  font-family: "Roboto Mono";
  font-style: normal;
  font-weight: 400;
  font-display: swap;
  src: url("/fonts/roboto-mono-latin-400-normal.woff2") format("woff2");
}

@font-face {
  font-family: "Roboto Mono";
  font-style: normal;
  font-weight: 600;
  font-display: swap;
  src: url("/fonts/roboto-mono-latin-600-normal.woff2") format("woff2");
}

:root {
  --bg: #fcfcfd;
  --surface: #ffffff;
  --ink: #101318;
  --text-2: #4f545c;
  --text-3: #6b7280;
  --rule: #dfe2e6;
  --rule-soft: #eef0f2;
  --rule-strong: #101318;
  --brand: #0b2a6b;
  --accent: #1e4fe0;
  --accent-soft: #e4eafe;
  --facet: #8a5b00;
  --facet-soft: #f7efdd;
  --ok: #127a45;
  --ok-soft: #e3f3e9;
  --bad: #a83232;
  --bad-soft: #f8e1e1;
  --bar-idle: #c9ced6;
  --code-bg: #f2f3f5;
  --lesson-ink: #101318;
  --lesson-muted: #4f545c;
  --lesson-rule: #dfe2e6;
  --lesson-accent: #1e4fe0;
  --lesson-accent-soft: #e4eafe;
  --lesson-title-size: 3rem;
  --lesson-section-size: 1.6875rem;
  --lesson-subsection-size: 1.1875rem;
  --lesson-body-size: 1.0625rem;
  --lesson-small-size: 0.9375rem;
  --lesson-meta-size: 0.625rem;
  --radius: 0;
  --font-display: "Archivo Variable", "Archivo", Arial, sans-serif;
  --font-ui: "Inter Variable", "Inter", Arial, sans-serif;
  --font-mono: "Roboto Mono", ui-monospace, monospace;
  --site-width: 65rem;
  --reading-width: 55rem;
  --paper: #ffffff;
  --muted: var(--text-2);
  color: var(--lesson-ink);
  background: var(--bg);
  font: 16px/1.55 var(--font-ui);
  font-synthesis: none;
  text-rendering: optimizeLegibility;
}

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

html {
  min-width: 20rem;
  background: var(--bg);
  color: var(--lesson-ink);
}

body {
  max-width: 44rem;
  margin: 0 auto;
  padding: 3.375rem 0 5rem;
  background: var(--bg);
  font-family: var(--font-ui);
  font-size: var(--lesson-body-size);
  line-height: 1.6;
  overflow-wrap: break-word;
}

[hidden] {
  display: none !important;
}

h1,
h2,
h3,
h4 {
  font-family: var(--font-display);
  line-height: 1.08;
}

h1 {
  margin: 0 0 0.75rem;
  font-size: var(--lesson-title-size);
  font-weight: 700;
  letter-spacing: -0.1125rem;
}

h2 {
  margin: 3rem 0 0.875rem;
  padding-top: 1rem;
  border-top: 2px solid var(--rule-strong);
  font-size: var(--lesson-section-size);
  font-weight: 700;
  letter-spacing: -0.04375rem;
}

h3 {
  margin: 1.75rem 0 0.5rem;
  font-size: var(--lesson-subsection-size);
  font-weight: 600;
  letter-spacing: -0.01875rem;
}

p {
  margin: 0 0 1rem;
}

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

:focus-visible {
  outline: 2px solid var(--lesson-accent);
  outline-offset: 3px;
}

.subtitle {
  margin-bottom: 0.75rem;
  color: var(--lesson-muted);
  font-size: var(--lesson-subsection-size);
  line-height: 1.45;
}

.meta,
nav.course {
  color: var(--text-3);
  font: 400 var(--lesson-meta-size)/1.4 var(--font-mono);
  letter-spacing: 0.0875rem;
  text-transform: uppercase;
}

.meta {
  margin-bottom: 3rem;
}

nav.course {
  margin-bottom: 2rem;
}

nav.course a + a::before {
  color: var(--text-3);
  content: " / ";
}

code,
pre {
  font-family: var(--font-mono);
  font-size: 0.9em;
}

code {
  padding: 0.1em 0.3em;
  border-radius: var(--radius);
  background: var(--code-bg);
}

pre {
  padding: 1rem 1.25rem;
  overflow-x: auto;
  border-left: 3px solid var(--lesson-rule);
  background: var(--code-bg);
  line-height: 1.45;
}

pre code {
  padding: 0;
  background: none;
}

hr {
  margin: 2.5rem 0;
  border: 0;
  border-top: 1px solid var(--rule);
}

.aside,
.claim {
  margin: 1.5rem 0;
  padding: 0.125rem 0 0.125rem 1.125rem;
  border-left: 2px solid var(--rule-strong);
  color: var(--lesson-muted);
  font-size: var(--lesson-small-size);
}

.claim .src {
  display: block;
  margin-top: 0.35rem;
  color: var(--text-3);
  font: 400 var(--lesson-meta-size)/1.4 var(--font-mono);
  letter-spacing: 0.0875rem;
  text-transform: uppercase;
}

.win {
  margin: 1.5rem 0;
  padding: 0.25rem 0 0.25rem 1.25rem;
  border-left: 6px solid var(--lesson-accent);
  border-radius: var(--radius);
  background: var(--bg);
}

.win strong {
  color: var(--lesson-accent);
}

.cite {
  color: var(--lesson-muted);
  font-size: 0.85rem;
}

sup a {
  text-decoration: none;
}

.card,
.quiz,
.sorter,
.recall {
  margin: 1.5rem 0;
  padding: 1.375rem;
  border: 1px solid var(--rule-strong);
  border-radius: var(--radius);
  background: var(--surface);
}

button,
textarea {
  border-radius: var(--radius);
  font: inherit;
}

button {
  padding: 0.5625rem 0.875rem;
  border: 1px solid var(--lesson-ink);
  background: var(--surface);
  color: var(--lesson-ink);
  cursor: pointer;
  font: 400 var(--lesson-meta-size)/1.3 var(--font-mono);
  letter-spacing: 0.0875rem;
  text-transform: uppercase;
}

button.primary {
  background: var(--lesson-ink);
  color: var(--surface);
}

button[disabled] {
  cursor: default;
  opacity: 0.45;
}

.row {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem;
}

.nav {
  display: flex;
  justify-content: space-between;
  margin-top: 3.25rem;
  padding-top: 1.125rem;
  border-top: 2px solid var(--rule-strong);
  font: 400 0.6875rem/1.4 var(--font-mono);
  letter-spacing: 0.0875rem;
  text-transform: uppercase;
}

.footer-note {
  margin-top: 3rem;
  padding-top: 1rem;
  border-top: 2px solid var(--rule-strong);
  color: var(--lesson-muted);
  font-size: var(--lesson-small-size);
}

table {
  width: 100%;
  margin: 1rem 0;
  border-collapse: collapse;
  font-size: var(--lesson-small-size);
}

th,
td {
  padding: 0.4rem 0.6rem;
  border-bottom: 1px solid var(--lesson-rule);
  text-align: left;
  vertical-align: top;
}

th {
  font-weight: 600;
}

.tag {
  display: inline-block;
  padding: 0.1em 0.45em;
  border: 1px solid var(--rule);
  border-radius: var(--radius);
  font: 400 0.72rem/1.4 var(--font-mono);
  letter-spacing: 0.04em;
  text-transform: uppercase;
  white-space: nowrap;
}

.tag.ok {
  border-color: var(--ok);
  background: var(--ok-soft);
  color: var(--ok);
}

.tag.weak {
  border-color: var(--facet);
  background: var(--facet-soft);
  color: var(--facet);
}

.tag.no {
  border-color: var(--bad);
  background: var(--bad-soft);
  color: var(--bad);
}

.quiz .q,
.recall .q,
.sorter .item {
  margin-bottom: 0.75rem;
  font: 700 var(--lesson-subsection-size)/1.25 var(--font-display);
  letter-spacing: -0.025rem;
}

.quiz .opts {
  display: grid;
  gap: 0.5rem;
}

.quiz label {
  display: block;
  margin: 0.3rem 0;
  cursor: pointer;
}

.quiz .opt {
  display: block;
  width: 100%;
  font-family: var(--font-mono);
  text-align: left;
}

.quiz .opt.right,
.sorter .bucket.right {
  border-color: var(--ok);
  background: var(--ok-soft);
}

.quiz .opt.wrong,
.sorter .bucket.wrong {
  border-color: var(--bad);
  background: var(--bad-soft);
}

.quiz .fb,
.quiz .result,
.sorter .fb {
  min-height: 1.4em;
  margin: 0.75rem 0 0;
  font-size: var(--lesson-small-size);
}

.quiz .fb.ok,
.quiz.ok .result,
.sorter .fb.ok {
  color: var(--ok);
}

.quiz .fb.no,
.quiz.bad .result,
.sorter .fb.no {
  color: var(--bad);
}

.sorter .buckets {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(9rem, 1fr));
  gap: 0.5rem;
}

.sorter .bucket {
  font-family: var(--font-mono);
  font-size: 0.85rem;
}

.sorter .score {
  margin-top: 0.5rem;
  color: var(--text-3);
  font-size: 0.85rem;
}

.recall textarea {
  width: 100%;
  min-height: 5.5rem;
  padding: 0.6rem;
  border: 1px solid var(--lesson-rule);
  background: var(--surface);
  color: var(--lesson-ink);
  font-size: var(--lesson-small-size);
}

.recall .model,
.recall .answer {
  margin-top: 1rem;
  padding-top: 0.8rem;
  border-top: 1px dashed var(--lesson-rule);
  font-size: var(--lesson-small-size);
}

.recall .model h4 {
  margin: 0 0 0.4rem;
  color: var(--text-3);
  font: 600 var(--lesson-meta-size)/1.4 var(--font-mono);
  letter-spacing: 0.0875rem;
  text-transform: uppercase;
}

.arr {
  height: 8rem;
  display: flex;
  align-items: flex-end;
  gap: 0.4rem;
  margin: 1rem 0;
}

.arr .bar {
  flex: 1;
  display: flex;
  align-items: flex-end;
  justify-content: center;
  padding-bottom: 0.25rem;
  border-radius: var(--radius);
  background: var(--bar-idle);
  font-family: var(--font-mono);
  font-size: 0.6875rem;
  transition: background-color 150ms ease-out, height 200ms ease-out;
}

.arr .bar.cmp {
  background: var(--lesson-accent);
  color: var(--surface);
}

.arr .bar.done {
  background: var(--ok);
  color: var(--surface);
}

.status {
  min-height: 1.4em;
  color: var(--lesson-muted);
  font-family: var(--font-mono);
  font-size: 0.9rem;
}

@media (hover: hover) and (pointer: fine) {
  a:hover {
    text-decoration-thickness: 2px;
  }

  button:hover {
    background: var(--code-bg);
  }

  button.primary:hover {
    background: var(--lesson-ink);
  }
}

@media (max-width: 40rem) {
  body {
    width: auto;
    padding: 1.875rem 1.25rem 2.75rem;
    font-size: 1rem;
  }

  h1 {
    font-size: 2.125rem;
    letter-spacing: -0.075rem;
  }

  h2 {
    margin-top: 2.25rem;
    font-size: 1.375rem;
    letter-spacing: -0.03125rem;
  }

  .subtitle {
    font-size: 1rem;
  }

  .meta {
    margin-bottom: 1.625rem;
  }

  .win {
    padding-left: 1rem;
    border-left-width: 5px;
  }

  .nav {
    flex-direction: column;
    align-items: flex-start;
    gap: 0.75rem;
  }

  table {
    display: block;
    overflow-x: auto;
  }

  .arr {
    height: 6.875rem;
  }
}

@media (prefers-reduced-motion: reduce) {
  .arr .bar {
    transition: background-color 80ms ease-out;
  }
}

@media print {
  body {
    max-width: none;
    padding: 0;
    background: var(--surface);
    font-size: 11pt;
  }

  button,
  .nav,
  .noprint {
    display: none !important;
  }

  a {
    color: inherit;
    text-decoration: none;
  }
}