/* learn.css — shared spine for the APF /learn content site.
   Tokens copied from public/index.html :root. StartLab layout + motion, APF palette. */
:root {
  --ink: #15233B;
  --paper: #F2F4F7;
  --white: #FFFFFF;
  --amber: #E8A23D;
  --teal: #2E8C8C;
  --teal-ink: #1f6b6b;
  --teal-t: rgba(46,140,140,.08);
  --amber-t: rgba(232,162,61,.10);
  --warn: #C9742E;
  --warn-ink: #9a5a14;
  --line: #D7DBE2;
  --ink-soft: #50607a;
  --display: "Bai Jamjuree", system-ui, sans-serif;
  --body: "IBM Plex Sans Thai", system-ui, sans-serif;
  --mono: "IBM Plex Mono", "IBM Plex Sans Thai", monospace;
  --ease: cubic-bezier(0.22, 1, 0.36, 1);
  --z-sticky: 100;
  --wrap: 1120px;
  --gut: clamp(20px, 5vw, 64px);
}
* { box-sizing: border-box; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
body {
  margin: 0; font-family: var(--body); color: var(--ink);
  background: var(--paper); line-height: 1.6; min-height: 100vh;
}
h1,h2,h3,.display { font-family: var(--display); line-height: 1.15; letter-spacing: -.01em; }
a { color: var(--teal-ink); }
/* IBM Plex Sans Thai has no italic — <em> renders invisibly on Thai. Site-wide
   non-italic emphasis (weight + teal ink) so <em> is visible across scripts. */
em { font-style: normal; font-weight: 600; color: var(--teal-ink); }
img,svg { max-width: 100%; }

/* skip link */
.skip { position: absolute; left: -999px; top: 8px; background: var(--ink); color: #fff;
  padding: 8px 14px; border-radius: 8px; z-index: 200; }
.skip:focus { left: 8px; }

/* focus visibility (a11y) */
:focus-visible { outline: 3px solid var(--amber); outline-offset: 2px; border-radius: 4px; }

/* layout */
.wrap { max-width: var(--wrap); margin-inline: auto; padding-inline: var(--gut); }
section.band { padding-block: clamp(56px, 9vw, 120px); }
section.band.tint { background: var(--white); }

/* sticky nav */
.nav { position: sticky; top: 0; z-index: var(--z-sticky); background: rgba(242,244,247,.85);
  backdrop-filter: saturate(1.4) blur(10px); border-bottom: 1px solid var(--line); }
.nav .row { display: flex; align-items: center; gap: 18px; height: 62px; }
.nav .logo { font-family: var(--display); font-weight: 700; font-size: 1.15rem; color: var(--ink);
  text-decoration: none; letter-spacing: .02em; }
.nav .links { display: flex; gap: 4px; margin-inline-start: auto; align-items: center; }
.nav .links a { color: var(--ink-soft); text-decoration: none; font-weight: 500; font-size: .92rem;
  padding: 8px 12px; border-radius: 8px; }
.nav .links a:hover, .nav .links a[aria-current="page"] { color: var(--ink); background: var(--white); }
/* specificity must beat `.nav .links a` (0,2,1) — the CTA lives inside .links */
.nav .links a.cta { background: var(--amber); color: var(--ink); font-weight: 600; padding: 9px 18px;
  border-radius: 10px; text-decoration: none; }
.nav .links a.cta:hover { filter: brightness(1.04); background: var(--amber); }
/* reference dropdown */
.dd { position: relative; }
.dd > button { font: inherit; font-size: .92rem; font-weight: 500; color: var(--ink-soft);
  background: none; border: 0; padding: 8px 12px; border-radius: 8px; cursor: pointer; }
.dd > button:hover, .dd[data-open="true"] > button { color: var(--ink); background: var(--white); }
.dd .menu { position: absolute; top: calc(100% + 6px); inset-inline-end: 0; min-width: 200px;
  background: var(--white); border: 1px solid var(--line); border-radius: 12px; padding: 6px;
  box-shadow: 0 12px 32px rgba(21,35,59,.12); display: none; }
.dd[data-open="true"] .menu { display: block; }
.dd .menu a { display: block; padding: 9px 12px; border-radius: 8px; color: var(--ink);
  text-decoration: none; font-size: .9rem; }
.dd .menu a:hover { background: var(--paper); }
/* language toggle */
.lang { display: inline-flex; border: 1px solid var(--line); border-radius: 9px; overflow: hidden; }
.lang button { font: inherit; font-size: .82rem; font-weight: 600; border: 0; background: var(--white);
  color: var(--ink-soft); padding: 7px 11px; cursor: pointer; }
.lang button[aria-pressed="true"] { background: var(--ink); color: #fff; }
/* mobile menu toggle */
.burger { display: none; }
@media (max-width: 860px) {
  .nav .links { display: none; }
  .nav .links.open { display: flex; position: absolute; top: 62px; inset-inline: 0; flex-direction: column;
    background: var(--white); border-bottom: 1px solid var(--line); padding: 10px var(--gut); gap: 2px; }
  .burger { display: inline-flex; margin-inline-start: auto; background: none; border: 1px solid var(--line);
    border-radius: 8px; padding: 8px 10px; cursor: pointer; font-size: 1.1rem; }
}

/* hero — NO eyebrow (PRODUCT.md ban). Lead with the h1. */
.hero { padding-block: clamp(64px, 11vw, 150px); }
/* max-width uses ch for the Latin poster measure; min(92vw, …) keeps the box inside the
   viewport on mobile, and overflow-wrap lets a long Thai run (no inter-word spaces) break
   instead of overflowing the box. Latin headings still balance normally within the measure. */
.hero h1 { font-size: clamp(2.1rem, 5.4vw, 4rem); font-weight: 700; margin: 0 0 .3em;
  max-width: min(92vw, 15ch); text-wrap: balance; overflow-wrap: break-word; }
.hero p.lede { font-size: clamp(1.05rem, 2vw, 1.35rem); color: var(--ink-soft); max-width: 56ch; margin: 0 0 1.6em; }
.btnrow { display: flex; gap: 14px; flex-wrap: wrap; }
.btn { display: inline-flex; align-items: center; gap: 8px; font-weight: 600; text-decoration: none;
  padding: 13px 24px; border-radius: 12px; font-size: 1rem; transition: transform .2s var(--ease); }
.btn.primary { background: var(--amber); color: var(--ink); }
.btn.ghost { background: var(--white); color: var(--ink); border: 1px solid var(--line); }
.btn:hover { transform: translateY(-2px); }

/* section headings */
.band h2 { font-size: clamp(1.6rem, 3.4vw, 2.6rem); font-weight: 700; margin: 0 0 .4em; max-width: 20ch; }
.band .sub { color: var(--ink-soft); font-size: 1.05rem; max-width: 60ch; margin: 0 0 2.2em; }

/* NOTE: no .card / .grid — the "identical card grids" pattern is a PRODUCT.md ban and is used 0×.
   Each section picks a content-fit treatment (.stack / .split / .flag / .rows / .prose / <dl>).
   Do NOT reintroduce a generic card grid. A framework name, when needed, is a normal-case .tag chip: */
.tag { display: inline-block; font-family: var(--body); font-weight: 600; font-size: .78rem;
  color: var(--teal-ink); background: var(--teal-t); padding: 3px 10px; border-radius: 999px; }

/* two-panel contrast (through vs beside) — NOT two cards */
.split { display: grid; gap: 0; grid-template-columns: 1fr 1fr; border: 1px solid var(--line);
  border-radius: 18px; overflow: hidden; }
.split > div { padding: clamp(22px, 3vw, 40px); }
.split > .bad { background: var(--paper); }
.split > .good { background: var(--teal-t); border-inline-start: 1px solid var(--line); }
/* twin .bad panels (why page: no .good seam between them) get the same divider */
.split > .bad + .bad { border-inline-start: 1px solid var(--line); }
@media (max-width: 640px) { .split { grid-template-columns: 1fr; } .split > .good { border-inline-start: 0; border-block-start: 1px solid var(--line); } .split > .bad + .bad { border-inline-start: 0; border-block-start: 1px solid var(--line); } }

/* flag rows (conflicts) — full-width, amber tint background, leading icon. NO side-stripe border. */
.flag { display: grid; grid-template-columns: auto 1fr; gap: 16px; align-items: start;
  background: var(--amber-t); border: 1px solid var(--line); border-radius: 14px; padding: 18px 20px; margin-block: 12px; }
.flag .mark { font-size: 1.4rem; line-height: 1; }
.flag code { font-family: var(--mono); font-size: .78rem; background: var(--white); padding: 2px 7px; border-radius: 6px; }

/* numbered prose rows (ELT) — asymmetric, not a card grid */
.rows { display: grid; gap: 4px; }
.rows .r { display: grid; grid-template-columns: 3rem 1fr; gap: 18px; padding: 22px 0; border-top: 1px solid var(--line); }
.rows .r .num { font-family: var(--display); font-size: 2rem; color: var(--amber); font-weight: 700; line-height: 1; }
.rows .r h3 { margin: 0 0 .3em; }

/* prose */
.prose { max-width: 68ch; }
.prose p, .prose li { color: var(--ink); font-size: 1.05rem; }
/* design-system-owned emphasis (UA default only, otherwise) */
.prose strong { font-weight: 600; color: var(--ink); }
.prose h2 { margin-top: 1.6em; }
.prose table { width: 100%; border-collapse: collapse; margin: 1.4em 0; font-size: .95rem; }
.prose th, .prose td { text-align: start; border: 1px solid var(--line); padding: 10px 12px; vertical-align: top; }
.prose th { background: var(--teal-t); font-family: var(--display); }
.prose code { font-family: var(--mono); background: var(--paper); padding: 1px 6px; border-radius: 6px; font-size: .88em; }

/* footer */
.foot { background: var(--ink); color: #cdd6e4; padding-block: 56px; }
.foot a { color: #cdd6e4; text-decoration: none; }
.foot a:hover { color: #fff; }
.foot .cc-badge { display: inline-flex; gap: 5px; color: #cdd6e4; flex: none; }
.foot .cc-badge:hover { color: #fff; }
.foot .cc-badge svg { width: 20px; height: 20px; display: block; }
.foot .cols { display: grid; gap: 32px; grid-template-columns: 1.4fr repeat(3, 1fr); }
.foot h4 { color: #fff; font-family: var(--display); font-size: .95rem; margin: 0 0 12px; }
.foot .cols ul { list-style: none; margin: 0; padding: 0; display: grid; gap: 8px; font-size: .9rem; }
.foot .fine { border-top: 1px solid rgba(255,255,255,.12); margin-top: 36px; padding-top: 20px;
  font-size: .82rem; color: #8a99b3; display: flex; align-items: center; gap: 12px; flex-wrap: wrap; }
@media (max-width: 720px) { .foot .cols { grid-template-columns: 1fr 1fr; } }

/* stack locator ("you are here" in the 5-layer spine) — injected under the hero
   lede on ref pages that map to one layer. 5 linked nodes, current lit amber.
   Quiet: display face, ink-soft, thin connectors. Not cards. */
.spine { display: flex; flex-wrap: wrap; align-items: center; margin: 1.4em 0 0; }
.spine a { display: inline-flex; align-items: center; gap: 7px; text-decoration: none;
  color: var(--ink-soft); font-family: var(--display); font-weight: 600; font-size: .8rem;
  letter-spacing: .02em; padding: 6px 0; }
.spine a .dot { width: 8px; height: 8px; border-radius: 50%; background: var(--line); flex: none; }
.spine a::after { content: ""; width: 22px; height: 1px; background: var(--line); margin: 0 9px; }
.spine a:last-child::after { display: none; }
.spine a[aria-current="page"] { color: var(--ink); }
.spine a[aria-current="page"] .dot { background: var(--amber); box-shadow: 0 0 0 3px var(--amber-t); }
.spine a:hover, .spine a:focus-visible { color: var(--teal-ink);
  text-decoration: underline; text-underline-offset: 3px; }

/* ---- diagrams (the page's real imagery) ---- */

/* fixed-column diagram grids cramp Thai text at ~390px (no @media collapse like
   .split/.foot). Collapse .stack .layer (7rem 1fr) + .rows .r (3rem 1fr) to one
   column; shrink the now-inline number cell so it reads as a label, not a poster. */
@media (max-width: 560px) {
  .stack .layer, .rows .r { grid-template-columns: 1fr; gap: 6px; }
  .rows .r .num { font-size: 1.4rem; }
}

/* layer stack (5 layers page + landing glance): 5 stacked bars, engine layers accented */
.stack { display: grid; gap: 10px; }
.stack .layer { display: grid; grid-template-columns: 7rem 1fr; gap: 18px; align-items: center;
  background: var(--white); border: 1px solid var(--line); border-radius: 14px; padding: 18px 22px; }
.stack .layer .name { font-family: var(--display); font-weight: 700; font-size: 1.35rem; }
.stack .layer .fw { font-size: .82rem; color: var(--ink-soft); }
.stack .layer[data-engine="true"] { border-color: var(--amber); background: var(--amber-t); }
.stack .layer[data-engine="true"] .name { color: var(--warn-ink); }

/* depth ladder: rungs that fill on scroll (width bar encodes depth) */
.ladder { display: grid; gap: 0; }
.ladder .rung { display: grid; grid-template-columns: 8rem 1fr; gap: 18px; align-items: center;
  padding: 16px 0; border-top: 1px solid var(--line); }
.ladder .rung .depth { font-family: var(--display); font-weight: 700; }
.ladder .rung .bar { height: 12px; border-radius: 999px; background: var(--teal); transform-origin: left;
  transform: scaleX(var(--fill, 1)); transition: transform .8s var(--ease); }
/* JS-scoped: without JS the reveal .in class is never added, so an unscoped :not(.in)
   would collapse every depth bar (scaleX 0) and destroy the depth encoding. Gate on .js so
   the no-JS fallback shows full bars (transform from .ladder .rung .bar above). */
.js .ladder .rung:not(.in) .bar { transform: scaleX(0); }
/* fills: shallow→deepest = .2 .4 .6 .8 1 set inline via style="--fill:.4" */

/* Octalysis octagon — THE signature element (DESIGN.md #3). SVG ring, white/black-hat halves. */
.octagon { max-width: 520px; margin-inline: auto; }
.octagon .seg { cursor: pointer; transition: opacity .3s var(--ease), transform .3s var(--ease); transform-origin: center; }
.octagon .seg:hover, .octagon .seg:focus-visible { opacity: .85; }
.octagon .seg[data-hat="white"] { fill: var(--teal); }
.octagon .seg[data-hat="black"] { fill: var(--ink); }
.octagon .seg[aria-selected="true"] { stroke: var(--amber); stroke-width: 3; }
.octagon text { fill: #fff; font-family: var(--display); font-size: 11px; }
.octa-detail { margin-top: 18px; min-height: 3.5em; }

/* reveal motion */
[data-reveal] { opacity: 1; transform: none; }
.js [data-reveal] { opacity: 0; transform: translateY(22px); transition: opacity .7s var(--ease), transform .7s var(--ease); }
.js [data-reveal].in { opacity: 1; transform: none; }
[data-reveal="delay-1"] { transition-delay: .08s; }
[data-reveal="delay-2"] { transition-delay: .16s; }
[data-reveal="delay-3"] { transition-delay: .24s; }

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  * { animation: none !important; }
  [data-reveal] { opacity: 1; transform: none; transition: none; }
  .btn:hover { transform: none; }
}