/* /learn: long-form lesson text, the hub groups and lesson navigation.
   Built on the tokens in site.css; nothing here overrides site.css components. */

/* ── hub ── */
.learn-chips { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 8px; }
.learn-chips .chip { display: inline-flex; align-items: center; }
.learn-feature { display: grid; grid-template-columns: minmax(0, 2fr) minmax(0, 3fr); overflow: hidden; }
.learn-feature-copy { display: grid; gap: 12px; align-content: center; padding: clamp(24px, 3vw, 40px); }
.learn-group { padding-block: clamp(28px, 4vw, 48px); }
.learn-group-head { display: flex; align-items: baseline; justify-content: space-between; gap: 16px;
  margin-bottom: 18px; padding-bottom: 12px; border-bottom: 1px solid var(--line); }
.learn-card p { display: -webkit-box; -webkit-line-clamp: 2; -webkit-box-orient: vertical; overflow: hidden; }
@media (max-width: 760px) { .learn-feature { grid-template-columns: 1fr; } }

/* ── lesson header ── */
.learn-tags { display: flex; flex-wrap: wrap; gap: 6px; }
.learn-title { font-size: clamp(1.9rem, 1.2rem + 2.2vw, 3rem); }
.learn-wrap { max-width: 760px; display: grid; grid-template-columns: minmax(0, 1fr); gap: 20px; }
.learn-wrap > *, .learn-prose > * { min-width: 0; max-width: 100%; }
.learn-wrap a { overflow-wrap: anywhere; }   /* long bare URLs in source lists must wrap on phones */
.learn-title { overflow-wrap: anywhere; }
.learn-video { border-radius: var(--r-lg); overflow: hidden; background: var(--surface);
  box-shadow: inset 0 0 0 1px var(--line); }
.learn-video { aspect-ratio: 16 / 9; }
.learn-video iframe { width: 100%; height: 100%; border: 0; }

/* ── lesson text ── */
.learn-prose { color: var(--text-2); font-size: 16.5px; line-height: 1.7; min-width: 0; }
.learn-prose > * + * { margin-top: 1.05em; }
.learn-prose h2 { margin-top: 2.2em; font-size: clamp(1.35rem, 1.1rem + .8vw, 1.75rem); line-height: 1.2; letter-spacing: -0.035em; }
.learn-prose h3 { margin-top: 1.8em; font-size: 1.15rem; line-height: 1.3; letter-spacing: -0.02em; }
.learn-prose h4 { margin-top: 1.5em; font-size: 1rem; }
.learn-prose h2 + *, .learn-prose h3 + *, .learn-prose h4 + * { margin-top: .6em; }
.learn-prose strong { color: var(--text); font-weight: 600; }
.learn-prose a { color: var(--text); text-decoration: underline; text-decoration-color: var(--amber-25);
  text-underline-offset: 3px; transition: text-decoration-color var(--dur, .2s); }
.learn-prose a:hover { text-decoration-color: var(--amber); }
.learn-prose ul, .learn-prose ol { padding-left: 1.3em; }
.learn-prose ul { list-style: disc; }
.learn-prose ol { list-style: decimal; }
.learn-prose li + li { margin-top: .35em; }
.learn-prose li::marker { color: var(--text-4); }
.learn-prose blockquote { padding: 2px 0 2px 16px; border-left: 2px solid var(--amber-25); color: var(--text-3); font-size: 14.5px; }
.learn-prose .learn-figure img { border-radius: var(--r-md); box-shadow: inset 0 0 0 1px var(--line); margin-inline: auto; }
.learn-prose .learn-pre { white-space: pre; overflow-x: auto; font-size: 12.5px; line-height: 1.6; }
.learn-prose .learn-pre:focus-visible { outline: 2px solid var(--amber); outline-offset: 2px; }

.learn-table-wrap { overflow-x: auto; border-radius: var(--r-lg); background: var(--surface); box-shadow: inset 0 0 0 1px var(--line); }
.learn-table-wrap:focus-visible { outline: 2px solid var(--amber); outline-offset: 2px; }
.learn-table-wrap table { width: 100%; font-size: 14px; line-height: 1.5; }
.learn-table-wrap th, .learn-table-wrap td { padding: 11px 14px; text-align: left; vertical-align: top; border-bottom: 1px solid var(--line); }
.learn-table-wrap th { font: 500 11px/1.4 var(--f-mono); letter-spacing: .04em; text-transform: uppercase; color: var(--text-3);
  background: var(--surface-2); }
.learn-table-wrap th strong { color: inherit; font-weight: inherit; }
.learn-table-wrap tr:last-child td { border-bottom: 0; }
.learn-cell-line { display: block; }
.learn-cell-line + .learn-cell-line { margin-top: .3em; }

.learn-callout { display: flex; gap: 12px; padding: 16px 18px; border-radius: var(--r-lg); background: var(--surface);
  box-shadow: inset 0 0 0 1px var(--line-2); font-size: 15px; }
.learn-callout.is-product { background: var(--amber-08); box-shadow: inset 0 0 0 1px var(--amber-25); }
.learn-callout > div > * + * { margin-top: .6em; }
.learn-callout-icon { flex: none; line-height: 1.7; }

/* ── glossary term index ── */
.learn-index { display: grid; gap: 18px; padding: 20px 22px; }
.learn-index ul { display: grid; grid-template-columns: repeat(auto-fill, minmax(190px, 1fr)); gap: 4px 20px; margin-top: 8px; }
.learn-index a { font-size: 14px; color: var(--text-3); }
.learn-index a:hover { color: var(--amber); }
.learn-index-sec { font: 500 11px var(--f-mono) !important; letter-spacing: .08em; text-transform: uppercase; }

/* ── lesson navigation ── */
.learn-nav { display: grid; gap: 14px; margin-top: 28px; padding-top: 24px; border-top: 1px solid var(--line); }
.learn-steps { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; }
.learn-step { display: grid; gap: 6px; padding: 16px 18px; font-size: 14.5px; color: var(--text); }
.learn-step.is-next { text-align: right; }
@media (max-width: 640px) { .learn-steps { grid-template-columns: 1fr; } .learn-step-empty { display: none; } }

/* ══ Hub contents layout. Every rule below is scoped to html:root (always matches, one class of weight over the base rules above).
   The hub's thumbnail images and "Lesson N · x min read" lines, the featured block's picture and the lesson banner stay in the
   markup built by build-learn.py and are hidden here. ══ */

/* lesson pages: no number-tile banner */
html:root .learn-banner { display: none; }

/* hub rows: no picture, no "Lesson N · x min read" line (number is its own element) */
html:root .learn-card .learn-thumb,
html:root .learn-card .meta { display: none; }
html:root .learn-card .learn-num { display: block; font-family: var(--f-mono); color: var(--text-3); font-feature-settings: "tnum"; }
html:root .learn-card .learn-num:empty::before { content: "\2013"; color: var(--text-4); }
html:root .learn-card { transition: background var(--dur, .26s), box-shadow var(--dur, .26s); }
html:root .learn-card h3 { transition: color var(--dur, .26s); }
html:root .learn-group { padding-block: clamp(20px, 3vw, 32px); }
html:root .learn-group-head { margin-bottom: 8px; padding-bottom: 10px; }
html:root .learn-group-head .note { white-space: nowrap; }
/* hub only: a shorter header and a tighter featured block, so the lists come up the page */
html:root #main > .phero:not(.learn-hero) { padding-top: calc(var(--header-h, 72px) + clamp(40px, 5vw, 72px)); padding-bottom: clamp(28px, 3vw, 40px); }
html:root #main > .phero:not(.learn-hero) + .section.tight { padding-block: clamp(28px, 3.5vw, 48px) 0; }
/* hub only: a shorter closing band */
html:root body:has(.learn-group) .cta-card { padding-block: clamp(32px, 4vw, 56px); }
html:root .learn-card:focus-visible { outline-offset: -2px; border-radius: var(--r-sm); }

/* Contents: one band per group, heading left (sticky), lessons right as number · title · description */
html:root .learn-group { border-top: 1px solid var(--line-2); padding-block: clamp(16px, 2.2vw, 24px); }
html:root .learn-group > .wrap { display: grid; grid-template-columns: minmax(200px, 280px) minmax(0, 1fr); column-gap: clamp(24px, 4vw, 64px); align-items: start; }
html:root .learn-group-head { position: sticky; top: calc(var(--header-h, 72px) + 24px); flex-direction: column; align-items: flex-start; gap: 8px;
  margin: 0; padding: 0; border: 0; }
html:root .learn-group .grid { display: block; }
html:root .learn-card { display: grid; grid-template-columns: 52px minmax(0, 5fr) minmax(0, 7fr); column-gap: 20px; align-items: baseline;
  padding: 11px 12px 11px 0; border-bottom: 1px solid var(--line); border-radius: 0; background: none; box-shadow: none; }
html:root .learn-group .grid > .learn-card:first-child { margin-top: -11px; }
html:root .learn-card .learn-num { font-size: 13px; padding-left: 2px; }
html:root .learn-card h3 { font: 500 16px/1.35 var(--f-sans); letter-spacing: -.01em; color: var(--text); }
html:root .learn-card p { font-size: 14px; line-height: 1.5; color: var(--text-3); -webkit-line-clamp: 2; }
html:root a.learn-card:hover { background: none; box-shadow: none; }
html:root a.learn-card:hover h3 { color: #fff; }
html:root a.learn-card:hover .learn-num { color: var(--amber); }
/* Featured block: the series overview drawn as the first band of the contents page, same two columns as the groups, no picture */
html:root #main > .phero:not(.learn-hero) + .section.tight.learn-featured { padding-block: clamp(16px, 2.2vw, 24px); }
html:root .learn-feature { display: grid; grid-template-columns: minmax(200px, 280px) minmax(0, 1fr); column-gap: clamp(24px, 4vw, 64px); row-gap: 10px;
  align-items: start; overflow: visible; border-radius: 0; background: none; box-shadow: none; }
html:root a.learn-feature:hover { background: none; box-shadow: none; }
html:root .learn-feature::before, html:root .learn-feature-art { display: none; }
html:root .learn-feature-copy { display: contents; }
html:root .learn-feature-head { display: flex; flex-direction: column; align-items: flex-start; gap: 8px; grid-column: 1; grid-row: 1 / span 3; padding-top: 11px; }
html:root .learn-feature-stats { display: block; font: 400 12px/1.4 var(--f-mono); letter-spacing: .02em; color: var(--text-3); font-feature-settings: "tnum"; }
html:root .learn-feature h2 { grid-column: 2; font-size: clamp(1.6rem, 1.15rem + 1.3vw, 2.25rem); line-height: 1.1; letter-spacing: -.035em; transition: color var(--dur, .26s); }
html:root .learn-feature p { grid-column: 2; max-width: 62ch; }
html:root .learn-feature .link { grid-column: 2; justify-self: start; margin-top: 6px; }
html:root a.learn-feature:hover h2 { color: #fff; }
html:root a.learn-feature:hover .link { color: var(--amber); background-size: 100% 1px; }
html:root a.learn-feature:hover .link .ic { transform: translateX(3px); }
html:root a.learn-feature:focus-visible { outline-offset: 8px; border-radius: var(--r-sm); }
@media (max-width: 900px) {
  html:root .learn-card { grid-template-columns: 40px minmax(0, 1fr); row-gap: 3px; align-items: start; }
  html:root .learn-card .learn-num { grid-row: 1 / span 2; line-height: 21.6px; }
  html:root .learn-card h3, html:root .learn-card p { grid-column: 2; }
}
@media (max-width: 760px) {
  html:root .learn-group > .wrap { grid-template-columns: minmax(0, 1fr); row-gap: 12px; }
  html:root .learn-group-head { position: static; flex-direction: row; align-items: baseline; justify-content: space-between; }
  html:root .learn-group .grid > .learn-card:first-child { margin-top: 0; }
  html:root .learn-group .grid { border-top: 1px solid var(--line); }
  html:root .learn-feature { grid-template-columns: minmax(0, 1fr); row-gap: 12px; }
  html:root .learn-feature-head { grid-column: 1; grid-row: auto; flex-direction: row; align-items: baseline; justify-content: space-between; gap: 16px; padding-top: 0; }
  html:root .learn-feature h2, html:root .learn-feature p, html:root .learn-feature .link { grid-column: 1; }
}

/* ── Hub: the series ends after the fifth track; Reference and Product guides are not lessons, so they sit on their own shelf ──
   (.learn-shelf wraps the groups build-learn.py marks .is-shelf, the ones whose pages have no lesson number.
   Scoped like the rest of the contents layout.) */
html:root .learn-shelf { margin-top: calc(3 * clamp(16px, 2.2vw, 24px));   /* last track's own padding + this = twice the gap between tracks */
  padding-top: calc(2 * clamp(16px, 2.2vw, 24px)); padding-bottom: clamp(24px, 3vw, 40px); border-top: 1px solid var(--line-3); }
html:root .learn-shelf-grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); column-gap: clamp(24px, 4vw, 64px); row-gap: 28px;
  width: min(100% - 2 * var(--gutter), var(--wrap)); margin-inline: auto; align-items: start; }
html:root .learn-shelf .learn-group { border-top: 0; padding-block: 0; min-width: 0; }
html:root .learn-shelf .learn-group > .wrap { display: block; width: auto; margin: 0; }
html:root .learn-shelf .learn-group-head { position: static; flex-direction: row; align-items: baseline; justify-content: space-between; gap: 16px;
  margin: 0; padding-bottom: 10px; border-bottom: 1px solid var(--line-2); }
html:root .learn-shelf .learn-group .grid { border-top: 0; }
html:root .learn-shelf .learn-card { grid-template-columns: minmax(0, 1fr); row-gap: 3px; align-items: start; padding-right: 0; }
html:root .learn-shelf .learn-card .learn-num { display: none; }   /* no lesson number, so no number column and no placeholder dash */
html:root .learn-shelf .learn-card h3, html:root .learn-shelf .learn-card p { grid-column: 1; }
html:root .learn-shelf .learn-group .grid > .learn-card:first-child { margin-top: 0; }
@media (max-width: 760px) {
  html:root .learn-shelf-grid { grid-template-columns: minmax(0, 1fr); row-gap: 36px; }
}