/* ============================================================
   CA IDMS Crash Course — design system
   ============================================================ */

:root {
  color-scheme: light dark;

  /* Brand: mainframe teal + amber terminal */
  --brand-50:  #eefbf7;
  --brand-100: #d3f4ea;
  --brand-200: #a8e8d7;
  --brand-300: #6fd5be;
  --brand-400: #35bda1;
  --brand-500: #14a087;
  --brand-600: #0b806e;
  --brand-700: #0b6659;
  --brand-800: #0d5148;
  --brand-900: #0d443d;

  --amber-300: #fcd34d;
  --amber-400: #fbbf24;
  --amber-500: #f59e0b;
  --amber-600: #d97706;

  --rose-400: #fb7185;
  --rose-500: #f43f5e;
  --rose-600: #e11d48;

  --violet-400: #a78bfa;
  --violet-500: #8b5cf6;

  --sky-400: #38bdf8;
  --sky-500: #0ea5e9;

  /* Semantic — light */
  --bg:            #f7f8f7;
  --bg-elev:       #ffffff;
  --bg-sunken:     #eef0ef;
  --bg-code:       #0f1c1a;
  --surface-hover: #f1f5f4;

  --text:      #0f1a18;
  --text-mute: #55635f;
  --text-faint:#7d8a86;

  --border:      #dfe4e2;
  --border-soft: #ebefed;
  --border-strong:#c6cecb;

  --accent:      var(--brand-600);
  --accent-hover:var(--brand-700);
  --accent-soft: var(--brand-50);
  --on-accent:   #ffffff;

  --ok:    #0b806e;
  --ok-bg: #e7f7f1;
  --warn:  #b45309;
  --warn-bg:#fdf3e3;
  --err:   #be123c;
  --err-bg:#fdeef1;
  --info:  #0369a1;
  --info-bg:#e8f4fd;

  --shadow-sm: 0 1px 2px rgb(15 26 24 / .06), 0 1px 1px rgb(15 26 24 / .04);
  --shadow-md: 0 4px 14px -4px rgb(15 26 24 / .12), 0 2px 4px -2px rgb(15 26 24 / .06);
  --shadow-lg: 0 18px 40px -18px rgb(15 26 24 / .28);

  --radius-xs: 6px;
  --radius-sm: 9px;
  --radius:    13px;
  --radius-lg: 20px;
  --radius-xl: 28px;

  --font-sans: "Inter var", "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI",
               Roboto, "Helvetica Neue", Arial, "Noto Sans", sans-serif;
  --font-mono: "JetBrains Mono", "IBM Plex Mono", ui-monospace, SFMono-Regular,
               "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;

  --shell-max: 1400px;
  --measure: 74ch;
  --nav-h: 60px;
  --sidebar-w: 300px;

  --ease: cubic-bezier(.22, 1, .36, 1);
}

html[data-theme="dark"] {
  color-scheme: dark;
  --bg:            #0b1211;
  --bg-elev:       #121b19;
  --bg-sunken:     #080e0d;
  --bg-code:       #060d0c;
  --surface-hover: #182422;

  --text:      #e8efec;
  --text-mute: #9aaba6;
  --text-faint:#71827d;

  --border:      #21302d;
  --border-soft: #1a2725;
  --border-strong:#31433f;

  --accent:      var(--brand-300);
  --accent-hover:var(--brand-200);
  --accent-soft: #0f2724;
  --on-accent:   #04211c;

  --ok:    #6fd5be;  --ok-bg:  #0d2b26;
  --warn:  var(--amber-300); --warn-bg:#2c2109;
  --err:   #fda4af;  --err-bg: #2e1119;
  --info:  #7dd3fc;  --info-bg:#0b2333;

  --shadow-sm: 0 1px 2px rgb(0 0 0 / .5);
  --shadow-md: 0 6px 18px -6px rgb(0 0 0 / .65);
  --shadow-lg: 0 22px 48px -20px rgb(0 0 0 / .8);
}

@media (prefers-color-scheme: dark) {
  html:not([data-theme="light"]) {
    color-scheme: dark;
    --bg:#0b1211; --bg-elev:#121b19; --bg-sunken:#080e0d; --bg-code:#060d0c;
    --surface-hover:#182422;
    --text:#e8efec; --text-mute:#9aaba6; --text-faint:#71827d;
    --border:#21302d; --border-soft:#1a2725; --border-strong:#31433f;
    --accent:var(--brand-300); --accent-hover:var(--brand-200);
    --accent-soft:#0f2724; --on-accent:#04211c;
    --ok:#6fd5be; --ok-bg:#0d2b26;
    --warn:var(--amber-300); --warn-bg:#2c2109;
    --err:#fda4af; --err-bg:#2e1119;
    --info:#7dd3fc; --info-bg:#0b2333;
    --shadow-sm:0 1px 2px rgb(0 0 0 / .5);
    --shadow-md:0 6px 18px -6px rgb(0 0 0 / .65);
    --shadow-lg:0 22px 48px -20px rgb(0 0 0 / .8);
  }
}

/* ---------- reset ---------- */
*, *::before, *::after { box-sizing: border-box; }
* { margin: 0; }
html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation-duration: .001ms !important; animation-iteration-count: 1 !important; transition-duration: .001ms !important; }
}
body {
  font-family: var(--font-sans);
  background: var(--bg);
  color: var(--text);
  line-height: 1.65;
  font-size: 16.5px;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  min-height: 100dvh;
}
img, svg, video { display: block; max-width: 100%; }
input, button, textarea, select { font: inherit; color: inherit; }
button { cursor: pointer; }
a { color: var(--accent); text-underline-offset: 3px; text-decoration-thickness: 1.5px; }
a:hover { color: var(--accent-hover); }
:where(h1,h2,h3,h4,h5) { line-height: 1.22; font-weight: 660; letter-spacing: -.018em; text-wrap: balance; }
p, li { text-wrap: pretty; }
hr { border: 0; border-top: 1px solid var(--border); margin: 2.4rem 0; }

:focus-visible {
  outline: 2.5px solid var(--accent);
  outline-offset: 2px;
  border-radius: 4px;
}

::selection { background: var(--brand-200); color: #0d443d; }
html[data-theme="dark"] ::selection { background: var(--brand-800); color: #eefbf7; }

.skip-link {
  position: absolute; left: 8px; top: -100px; z-index: 200;
  background: var(--accent); color: var(--on-accent);
  padding: .7rem 1.1rem; border-radius: var(--radius-sm); font-weight: 600;
  transition: top .18s var(--ease);
}
.skip-link:focus { top: 8px; }

.visually-hidden {
  position: absolute !important; width: 1px; height: 1px;
  padding: 0; margin: -1px; overflow: hidden;
  clip: rect(0 0 0 0); clip-path: inset(50%); white-space: nowrap; border: 0;
}

/* ============================================================
   Top navigation
   ============================================================ */
.topbar {
  position: sticky; top: 0; z-index: 60;
  height: var(--nav-h);
  display: flex; align-items: center; gap: .85rem;
  padding: 0 clamp(.85rem, 3vw, 1.6rem);
  background: color-mix(in oklab, var(--bg-elev) 86%, transparent);
  backdrop-filter: saturate(180%) blur(14px);
  -webkit-backdrop-filter: saturate(180%) blur(14px);
  border-bottom: 1px solid var(--border);
}
.brand {
  display: inline-flex; align-items: center; gap: .6rem;
  font-weight: 700; letter-spacing: -.02em; color: var(--text);
  text-decoration: none; white-space: nowrap; flex-shrink: 0;
}
.brand:hover { color: var(--text); }
.brand-mark {
  width: 30px; height: 30px; border-radius: 8px; flex-shrink: 0;
  background: linear-gradient(140deg, var(--brand-400), var(--brand-700) 62%, var(--brand-900));
  display: grid; place-items: center;
  color: #fff; font-family: var(--font-mono); font-size: .78rem; font-weight: 700;
  box-shadow: inset 0 1px 0 rgb(255 255 255 / .28);
}
.brand-text small {
  display: block; font-size: .66rem; font-weight: 500; letter-spacing: .1em;
  text-transform: uppercase; color: var(--text-faint); line-height: 1;
}
.brand-text span { font-size: .98rem; line-height: 1.15; }

.topbar-spacer { flex: 1; }
.topbar-actions { display: flex; align-items: center; gap: .4rem; }

.icon-btn {
  width: 38px; height: 38px; display: grid; place-items: center;
  border: 1px solid var(--border); border-radius: var(--radius-sm);
  background: var(--bg-elev); color: var(--text-mute);
  transition: background .15s, color .15s, border-color .15s;
}
.icon-btn:hover { background: var(--surface-hover); color: var(--text); border-color: var(--border-strong); }
.icon-btn svg { width: 18px; height: 18px; }

.nav-progress {
  display: none; align-items: center; gap: .55rem;
  font-size: .78rem; color: var(--text-mute); font-variant-numeric: tabular-nums;
}
@media (min-width: 720px) { .nav-progress { display: flex; } }
.nav-progress-track {
  width: 104px; height: 6px; border-radius: 99px; background: var(--bg-sunken);
  overflow: hidden; border: 1px solid var(--border-soft);
}
.nav-progress-fill {
  height: 100%; width: 0%; border-radius: 99px;
  background: linear-gradient(90deg, var(--brand-400), var(--brand-600));
  transition: width .5s var(--ease);
}

.menu-btn { display: grid; }
@media (min-width: 1060px) { .menu-btn { display: none; } }

/* ============================================================
   Shell layout
   ============================================================ */
.shell {
  max-width: var(--shell-max);
  margin: 0 auto;
  display: grid;
  grid-template-columns: 1fr;
  gap: 0;
}
@media (min-width: 1060px) {
  .shell.has-sidebar { grid-template-columns: var(--sidebar-w) minmax(0, 1fr); }
}

/* --- Sidebar / course outline --- */
.sidebar {
  position: fixed; inset: var(--nav-h) auto 0 0; z-index: 55;
  width: min(88vw, 340px);
  background: var(--bg-elev);
  border-right: 1px solid var(--border);
  overflow-y: auto; overscroll-behavior: contain;
  padding: 1.1rem .9rem 3rem;
  transform: translateX(-102%);
  transition: transform .28s var(--ease);
  box-shadow: var(--shadow-lg);
}
.sidebar[data-open="true"] { transform: none; }
@media (min-width: 1060px) {
  .sidebar {
    position: sticky; top: var(--nav-h); inset: auto;
    width: auto; height: calc(100dvh - var(--nav-h));
    transform: none; box-shadow: none; background: transparent;
    border-right: 1px solid var(--border);
  }
}
.sidebar-scrim {
  position: fixed; inset: 0; z-index: 50; background: rgb(3 10 9 / .5);
  backdrop-filter: blur(2px); opacity: 0; pointer-events: none; transition: opacity .25s;
}
.sidebar-scrim[data-open="true"] { opacity: 1; pointer-events: auto; }
@media (min-width: 1060px) { .sidebar-scrim { display: none; } }

.side-title {
  font-size: .69rem; text-transform: uppercase; letter-spacing: .13em;
  color: var(--text-faint); font-weight: 700; padding: .3rem .65rem .55rem;
}
.side-list { list-style: none; padding: 0; margin: 0 0 1.2rem; display: grid; gap: 2px; }
.side-link {
  display: grid; grid-template-columns: 26px 1fr auto; align-items: center; gap: .55rem;
  padding: .5rem .65rem; border-radius: var(--radius-sm);
  color: var(--text-mute); text-decoration: none; font-size: .875rem; line-height: 1.35;
  border: 1px solid transparent;
  transition: background .14s, color .14s;
}
.side-link:hover { background: var(--surface-hover); color: var(--text); }
.side-link[aria-current="page"] {
  background: var(--accent-soft); color: var(--text); font-weight: 600;
  border-color: color-mix(in oklab, var(--accent) 28%, transparent);
}
.side-num {
  font-family: var(--font-mono); font-size: .7rem; font-weight: 600;
  color: var(--text-faint); text-align: center;
  border: 1px solid var(--border); border-radius: 6px; padding: 1px 0;
}
.side-link[aria-current="page"] .side-num { color: var(--accent); border-color: var(--accent); }
.side-check { width: 15px; height: 15px; color: var(--ok); opacity: 0; }
.side-link[data-done="true"] .side-check { opacity: 1; }
.side-link[data-done="true"] .side-num { color: var(--ok); border-color: color-mix(in oklab, var(--ok) 45%, transparent); }

/* --- Main --- */
.main { min-width: 0; padding: 0 clamp(1rem, 4vw, 2.6rem) 5rem; }
.prose { max-width: var(--measure); }
.wide { max-width: 100%; }

/* ============================================================
   Typography blocks
   ============================================================ */
.page-head { padding: clamp(1.6rem, 5vw, 3rem) 0 1.2rem; }
.eyebrow {
  display: inline-flex; align-items: center; gap: .5rem;
  font-size: .74rem; font-weight: 700; letter-spacing: .11em; text-transform: uppercase;
  color: var(--accent); margin-bottom: .75rem;
}
.eyebrow::before {
  content: ""; width: 22px; height: 2px; border-radius: 2px; background: currentColor;
}
h1 { font-size: clamp(1.85rem, 1.2rem + 2.5vw, 2.85rem); letter-spacing: -.03em; }
h2 {
  font-size: clamp(1.32rem, 1.05rem + 1vw, 1.72rem);
  margin: 3.1rem 0 .9rem; padding-top: .3rem; scroll-margin-top: calc(var(--nav-h) + 14px);
}
h3 {
  font-size: clamp(1.08rem, .98rem + .45vw, 1.24rem);
  margin: 2.1rem 0 .65rem; scroll-margin-top: calc(var(--nav-h) + 14px);
}
h4 { font-size: 1rem; margin: 1.5rem 0 .45rem; color: var(--text); }
.lede { font-size: clamp(1.02rem, .97rem + .3vw, 1.16rem); color: var(--text-mute); max-width: 62ch; }
.prose p { margin: 0 0 1.05rem; }
.prose ul, .prose ol { margin: 0 0 1.15rem; padding-left: 1.35rem; display: grid; gap: .42rem; }
.prose li::marker { color: var(--text-faint); }
.prose strong { font-weight: 650; color: var(--text); }
.prose em { color: var(--text); }

.meta-row {
  display: flex; flex-wrap: wrap; gap: .5rem .9rem; align-items: center;
  margin-top: 1.1rem; font-size: .82rem; color: var(--text-mute);
}
.meta-row .dot { width: 3px; height: 3px; border-radius: 99px; background: var(--text-faint); }

/* code */
code {
  font-family: var(--font-mono); font-size: .875em;
  background: var(--bg-sunken); border: 1px solid var(--border-soft);
  padding: .1em .38em; border-radius: 5px; word-break: break-word;
}
pre {
  margin: 1.2rem 0; padding: 1.05rem 1.15rem;
  background: var(--bg-code); color: #d6e6e1;
  border-radius: var(--radius); border: 1px solid #1d302c;
  overflow-x: auto; font-size: .84rem; line-height: 1.62;
  -webkit-overflow-scrolling: touch;
}
pre code { background: none; border: 0; padding: 0; font-size: inherit; color: inherit; }
.code-block { position: relative; }
.code-block > figcaption {
  display: flex; align-items: center; justify-content: space-between; gap: 1rem;
  font-family: var(--font-mono); font-size: .72rem; letter-spacing: .04em;
  color: var(--text-faint); text-transform: uppercase;
  padding: .5rem .9rem; background: var(--bg-sunken);
  border: 1px solid var(--border); border-bottom: 0;
  border-radius: var(--radius) var(--radius) 0 0;
}
.code-block > figcaption + pre { margin-top: 0; border-radius: 0 0 var(--radius) var(--radius); }
.copy-btn {
  border: 1px solid var(--border); background: var(--bg-elev); color: var(--text-mute);
  border-radius: 6px; padding: .12rem .5rem; font-size: .68rem; font-family: var(--font-sans);
  letter-spacing: .02em; text-transform: none;
}
.copy-btn:hover { color: var(--text); border-color: var(--border-strong); }

/* syntax tint (applied by app.js) */
.tok-kw  { color: #7fd3bb; font-weight: 600; }
.tok-str { color: #f6c177; }
.tok-num { color: #c4b5fd; }
.tok-com { color: #6b8079; font-style: italic; }
.tok-id  { color: #9fd0ff; }

/* ============================================================
   Callouts
   ============================================================ */
.callout {
  --c: var(--info); --cbg: var(--info-bg);
  display: grid; grid-template-columns: auto 1fr; gap: .8rem;
  margin: 1.5rem 0; padding: .95rem 1.1rem;
  background: var(--cbg); border: 1px solid color-mix(in oklab, var(--c) 30%, transparent);
  border-left: 3px solid var(--c); border-radius: var(--radius-sm);
  font-size: .93rem;
}
.callout > svg { width: 19px; height: 19px; color: var(--c); margin-top: .18rem; flex-shrink: 0; }
.callout p:last-child { margin-bottom: 0; }
.callout-title { font-weight: 680; color: var(--text); display: block; margin-bottom: .18rem; }
.callout.warn { --c: var(--warn); --cbg: var(--warn-bg); }
.callout.danger { --c: var(--err); --cbg: var(--err-bg); }
.callout.ok { --c: var(--ok); --cbg: var(--ok-bg); }
.callout.rdrs { --c: var(--violet-500); --cbg: color-mix(in oklab, var(--violet-500) 9%, var(--bg-elev)); }

/* ============================================================
   Cards & grids
   ============================================================ */
.grid { display: grid; gap: 1rem; }
.grid.cols-2 { grid-template-columns: repeat(auto-fit, minmax(min(100%, 260px), 1fr)); }
.grid.cols-3 { grid-template-columns: repeat(auto-fit, minmax(min(100%, 210px), 1fr)); }
.grid.cols-4 { grid-template-columns: repeat(auto-fit, minmax(min(100%, 165px), 1fr)); }

.card {
  background: var(--bg-elev); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 1.15rem 1.2rem;
}
.card h3, .card h4 { margin-top: 0; }
.card p:last-child { margin-bottom: 0; }
.card-link { text-decoration: none; color: inherit; display: block; transition: border-color .16s, transform .16s var(--ease), box-shadow .16s; }
.card-link:hover { border-color: var(--accent); transform: translateY(-2px); box-shadow: var(--shadow-md); color: inherit; }

.stat { display: grid; gap: .1rem; }
.stat-num { font-size: 1.65rem; font-weight: 700; letter-spacing: -.03em; color: var(--accent); font-variant-numeric: tabular-nums; }
.stat-label { font-size: .78rem; color: var(--text-mute); }

.tag {
  display: inline-flex; align-items: center; gap: .3rem;
  font-size: .7rem; font-weight: 650; letter-spacing: .05em; text-transform: uppercase;
  padding: .18rem .5rem; border-radius: 99px;
  background: var(--bg-sunken); color: var(--text-mute); border: 1px solid var(--border);
}
.tag.accent { background: var(--accent-soft); color: var(--accent); border-color: color-mix(in oklab, var(--accent) 35%, transparent); }
.tag.violet { background: color-mix(in oklab, var(--violet-500) 12%, var(--bg-elev)); color: var(--violet-500); border-color: color-mix(in oklab, var(--violet-500) 35%, transparent); }
html[data-theme="dark"] .tag.violet { color: var(--violet-400); }

/* ============================================================
   Tables
   ============================================================ */
.table-wrap {
  overflow-x: auto; -webkit-overflow-scrolling: touch;
  border: 1px solid var(--border); border-radius: var(--radius);
  margin: 1.4rem 0; background: var(--bg-elev);
}
table { border-collapse: collapse; width: 100%; font-size: .88rem; min-width: 460px; }
caption { text-align: left; padding: .75rem 1rem; font-size: .8rem; color: var(--text-mute); border-bottom: 1px solid var(--border); }
th, td { padding: .62rem .85rem; text-align: left; border-bottom: 1px solid var(--border-soft); vertical-align: top; }
thead th {
  background: var(--bg-sunken); font-size: .72rem; text-transform: uppercase;
  letter-spacing: .06em; color: var(--text-mute); font-weight: 700;
  position: sticky; top: 0;
}
tbody tr:last-child td { border-bottom: 0; }
tbody tr:hover { background: var(--surface-hover); }
td code { font-size: .82em; }

/* ============================================================
   Interactive widget frame
   ============================================================ */
.lab {
  margin: 1.8rem 0; border: 1px solid var(--border); border-radius: var(--radius-lg);
  background: var(--bg-elev); overflow: hidden; box-shadow: var(--shadow-sm);
}
.lab-head {
  display: flex; flex-wrap: wrap; align-items: center; gap: .6rem;
  padding: .8rem 1.05rem; border-bottom: 1px solid var(--border);
  background: linear-gradient(180deg, var(--bg-sunken), transparent);
}
.lab-head h3, .lab-head h4 { margin: 0; font-size: .98rem; }
.lab-head .tag { margin-left: auto; }
.lab-body { padding: 1.05rem; }
.lab-foot {
  padding: .75rem 1.05rem; border-top: 1px solid var(--border);
  background: var(--bg-sunken); font-size: .82rem; color: var(--text-mute);
}

.btn {
  display: inline-flex; align-items: center; justify-content: center; gap: .45rem;
  padding: .55rem 1rem; border-radius: var(--radius-sm);
  border: 1px solid var(--border-strong); background: var(--bg-elev); color: var(--text);
  font-size: .875rem; font-weight: 570; white-space: nowrap;
  transition: background .14s, border-color .14s, transform .1s;
}
.btn:hover { background: var(--surface-hover); border-color: var(--accent); }
.btn:active { transform: translateY(1px); }
.btn[disabled] { opacity: .45; cursor: not-allowed; }
.btn.primary { background: var(--accent); border-color: var(--accent); color: var(--on-accent); }
.btn.primary:hover { background: var(--accent-hover); border-color: var(--accent-hover); }
.btn.ghost { border-color: transparent; background: transparent; color: var(--text-mute); }
.btn.ghost:hover { background: var(--surface-hover); color: var(--text); }
.btn.sm { padding: .34rem .68rem; font-size: .8rem; }
.btn svg { width: 15px; height: 15px; }

.btn-row { display: flex; flex-wrap: wrap; gap: .5rem; }

.field { display: grid; gap: .3rem; }
.field label { font-size: .78rem; font-weight: 620; color: var(--text-mute); }
input[type="text"], input[type="number"], select, textarea {
  width: 100%; padding: .52rem .7rem;
  border: 1px solid var(--border-strong); border-radius: var(--radius-sm);
  background: var(--bg); color: var(--text); font-size: .9rem;
}
input[type="range"] { width: 100%; accent-color: var(--accent); }
textarea { font-family: var(--font-mono); font-size: .84rem; resize: vertical; }
input:focus-visible, select:focus-visible, textarea:focus-visible { outline-offset: 1px; }

/* Terminal-ish console */
.console {
  background: var(--bg-code); color: #cfe3dd; border-radius: var(--radius);
  border: 1px solid #1d302c; padding: .85rem 1rem;
  font-family: var(--font-mono); font-size: .81rem; line-height: 1.6;
  max-height: 340px; overflow-y: auto; overscroll-behavior: contain;
}
.console .ln { display: block; white-space: pre-wrap; word-break: break-word; }
.console .ln.cmd { color: #9fd0ff; }
.console .ln.ok { color: #7fd3bb; }
.console .ln.err { color: #fda4af; }
.console .ln.note { color: #8fa39d; }
.console .ln.hl { color: #f6c177; }

.prompt-row { display: flex; gap: .5rem; margin-top: .7rem; }
.prompt-row input {
  font-family: var(--font-mono); font-size: .84rem;
  background: var(--bg-code); color: #d6e6e1; border-color: #26403a;
}
html[data-theme="light"] .prompt-row input,
html:not([data-theme="dark"]) .prompt-row input { color: #d6e6e1; }

/* Currency / state table */
.state-grid { display: grid; gap: .5rem; grid-template-columns: repeat(auto-fit, minmax(min(100%, 150px), 1fr)); }
.state-cell {
  border: 1px solid var(--border); border-radius: var(--radius-sm);
  padding: .5rem .65rem; background: var(--bg-sunken);
}
.state-cell dt { font-size: .68rem; text-transform: uppercase; letter-spacing: .07em; color: var(--text-faint); font-weight: 700; }
.state-cell dd { margin: .15rem 0 0; font-family: var(--font-mono); font-size: .8rem; word-break: break-all; }
.state-cell.changed { border-color: var(--accent); background: var(--accent-soft); animation: pulse .6s var(--ease); }
@keyframes pulse { from { transform: scale(.985); } to { transform: scale(1); } }

/* ============================================================
   Quiz
   ============================================================ */
.quiz { display: grid; gap: 1rem; }
.q { border: 1px solid var(--border); border-radius: var(--radius); padding: 1rem 1.1rem; background: var(--bg-elev); }
.q-stem { font-weight: 600; margin-bottom: .2rem; }
.q-stem .qn { color: var(--text-faint); font-family: var(--font-mono); font-size: .82em; margin-right: .45rem; }
.q-sub { font-size: .85rem; color: var(--text-mute); margin-bottom: .7rem; }
.opts { display: grid; gap: .4rem; margin-top: .6rem; }
.opt {
  display: grid; grid-template-columns: auto 1fr; gap: .6rem; align-items: start;
  padding: .55rem .7rem; border: 1px solid var(--border); border-radius: var(--radius-sm);
  cursor: pointer; font-size: .9rem; background: var(--bg);
  transition: border-color .14s, background .14s;
}
.opt:hover { border-color: var(--border-strong); background: var(--surface-hover); }
.opt input { margin-top: .28rem; accent-color: var(--accent); }
.opt.correct { border-color: var(--ok); background: var(--ok-bg); }
.opt.wrong { border-color: var(--err); background: var(--err-bg); }
.opt.missed { border-color: var(--warn); background: var(--warn-bg); }
.q-fb {
  margin-top: .7rem; font-size: .87rem; padding: .6rem .8rem;
  border-radius: var(--radius-sm); border: 1px solid var(--border);
  background: var(--bg-sunken); display: none;
}
.q-fb[data-show="true"] { display: block; }
.q-fb b { color: var(--text); }
.quiz-score {
  display: flex; flex-wrap: wrap; align-items: center; gap: .8rem;
  font-size: .9rem; padding: .7rem .9rem; border-radius: var(--radius-sm);
  border: 1px dashed var(--border-strong); background: var(--bg-sunken);
}
.score-badge {
  font-family: var(--font-mono); font-weight: 700; font-size: 1.05rem;
  padding: .1rem .55rem; border-radius: 7px; background: var(--accent-soft); color: var(--accent);
}
.score-badge.pass { background: var(--ok-bg); color: var(--ok); }
.score-badge.fail { background: var(--err-bg); color: var(--err); }

/* ============================================================
   Diagrams
   ============================================================ */
.diagram {
  margin: 1.5rem 0; padding: 1rem; border: 1px solid var(--border);
  border-radius: var(--radius); background: var(--bg-elev); overflow-x: auto;
}
.diagram svg { min-width: 460px; width: 100%; height: auto; }
.diagram figcaption { margin-top: .7rem; font-size: .82rem; color: var(--text-mute); }
.d-box { fill: var(--bg-sunken); stroke: var(--border-strong); }
.d-box-accent { fill: var(--accent-soft); stroke: var(--accent); }
.d-text { fill: var(--text); font-family: var(--font-sans); font-size: 12px; font-weight: 600; }
.d-sub { fill: var(--text-mute); font-family: var(--font-mono); font-size: 10px; font-weight: 500; }
.d-line { stroke: var(--border-strong); stroke-width: 1.6; fill: none; }
.d-line-accent { stroke: var(--accent); stroke-width: 2; fill: none; }
.d-label { fill: var(--text-faint); font-family: var(--font-mono); font-size: 9.5px; }

/* ============================================================
   Home page hero + module cards
   ============================================================ */
.hero {
  padding: clamp(2.4rem, 8vw, 5rem) 0 clamp(1.5rem, 4vw, 2.5rem);
  border-bottom: 1px solid var(--border);
}
.hero h1 { max-width: 17ch; }
.hero .lede { margin-top: 1.1rem; }
.hero-cta { display: flex; flex-wrap: wrap; gap: .65rem; margin-top: 1.8rem; }
.hero-stats {
  display: grid; grid-template-columns: repeat(auto-fit, minmax(120px, 1fr));
  gap: 1rem; margin-top: 2.4rem; padding-top: 1.6rem; border-top: 1px solid var(--border-soft);
}

.mod-card {
  display: grid; gap: .5rem; position: relative;
  background: var(--bg-elev); border: 1px solid var(--border);
  border-radius: var(--radius); padding: 1.1rem 1.15rem;
  text-decoration: none; color: inherit;
  transition: border-color .16s, transform .16s var(--ease), box-shadow .16s;
}
.mod-card:hover { border-color: var(--accent); transform: translateY(-2px); box-shadow: var(--shadow-md); color: inherit; }
.mod-card-top { display: flex; align-items: center; gap: .55rem; }
.mod-num {
  font-family: var(--font-mono); font-size: .72rem; font-weight: 700;
  color: var(--accent); background: var(--accent-soft);
  border: 1px solid color-mix(in oklab, var(--accent) 30%, transparent);
  border-radius: 6px; padding: .1rem .4rem;
}
.mod-card h3 { font-size: 1.02rem; margin: 0; }
.mod-card p { font-size: .87rem; color: var(--text-mute); margin: 0; }
.mod-card-foot {
  display: flex; flex-wrap: wrap; gap: .4rem; margin-top: .25rem;
  font-size: .72rem; color: var(--text-faint);
}
.mod-done {
  position: absolute; top: .9rem; right: 1rem; width: 17px; height: 17px;
  color: var(--ok); opacity: 0;
}
.mod-card[data-done="true"] .mod-done { opacity: 1; }
.mod-card[data-done="true"] { border-color: color-mix(in oklab, var(--ok) 40%, var(--border)); }

/* ============================================================
   Pager / footer
   ============================================================ */
.pager {
  display: grid; gap: .75rem; margin-top: 3.4rem; padding-top: 1.6rem;
  border-top: 1px solid var(--border);
  grid-template-columns: 1fr;
}
@media (min-width: 640px) { .pager { grid-template-columns: 1fr 1fr; } }
.pager a {
  display: grid; gap: .1rem; padding: .85rem 1rem; text-decoration: none;
  border: 1px solid var(--border); border-radius: var(--radius); background: var(--bg-elev);
  color: inherit; transition: border-color .15s, background .15s;
}
.pager a:hover { border-color: var(--accent); background: var(--surface-hover); color: inherit; }
.pager .dir { font-size: .72rem; text-transform: uppercase; letter-spacing: .08em; color: var(--text-faint); font-weight: 700; }
.pager .ttl { font-weight: 620; font-size: .93rem; }
.pager a.next { text-align: right; }

.complete-bar {
  display: flex; flex-wrap: wrap; align-items: center; gap: .8rem;
  margin-top: 2.6rem; padding: 1rem 1.15rem;
  border: 1px solid var(--border); border-radius: var(--radius);
  background: var(--bg-elev);
}
.complete-bar p { margin: 0; font-size: .88rem; color: var(--text-mute); flex: 1 1 240px; }

footer.site {
  border-top: 1px solid var(--border); margin-top: 3rem;
  padding: 2rem clamp(1rem, 4vw, 2.6rem);
  font-size: .82rem; color: var(--text-faint);
}
footer.site a { color: var(--text-mute); }

/* on-page TOC */
.toc {
  position: sticky; top: calc(var(--nav-h) + 1.2rem);
  align-self: start; font-size: .82rem; display: none;
}
@media (min-width: 1360px) { .toc { display: block; } }
.toc ul { list-style: none; padding: 0; margin: .5rem 0 0; display: grid; gap: 1px; border-left: 1px solid var(--border); }
.toc a { display: block; padding: .28rem .8rem; color: var(--text-mute); text-decoration: none; border-left: 2px solid transparent; margin-left: -1px; }
.toc a:hover { color: var(--text); }
.toc a[data-active="true"] { color: var(--accent); border-left-color: var(--accent); font-weight: 600; }
.toc .lvl3 a { padding-left: 1.5rem; font-size: .95em; }
.main-with-toc { display: grid; grid-template-columns: minmax(0,1fr); gap: 2.5rem; }
@media (min-width: 1360px) { .main-with-toc { grid-template-columns: minmax(0,1fr) 210px; } }

/* misc */
.kbd {
  font-family: var(--font-mono); font-size: .76em; padding: .1em .4em;
  border: 1px solid var(--border-strong); border-bottom-width: 2px;
  border-radius: 5px; background: var(--bg-elev); color: var(--text-mute);
}
details.exercise {
  border: 1px solid var(--border); border-radius: var(--radius);
  padding: .1rem .9rem; margin: 1.2rem 0; background: var(--bg-elev);
}
details.exercise > summary {
  cursor: pointer; font-weight: 620; padding: .8rem 0; font-size: .93rem;
  list-style: none; display: flex; align-items: center; gap: .5rem;
}
details.exercise > summary::-webkit-details-marker { display: none; }
details.exercise > summary::before {
  content: "▸"; color: var(--accent); transition: transform .2s var(--ease); display: inline-block;
}
details.exercise[open] > summary::before { transform: rotate(90deg); }
details.exercise > summary:hover { color: var(--accent); }
details.exercise > *:not(summary) { margin-bottom: .9rem; }

.split { display: grid; gap: 1rem; grid-template-columns: 1fr; }
@media (min-width: 820px) { .split.two { grid-template-columns: 1fr 1fr; } }
@media (min-width: 920px) { .split.side { grid-template-columns: 1.25fr .9fr; } }

.legend { display: flex; flex-wrap: wrap; gap: .55rem 1rem; font-size: .78rem; color: var(--text-mute); margin-top: .7rem; }
.legend span { display: inline-flex; align-items: center; gap: .35rem; }
.swatch { width: 11px; height: 11px; border-radius: 3px; border: 1px solid var(--border-strong); }

.scroll-x { overflow-x: auto; -webkit-overflow-scrolling: touch; }

/* print */
@media print {
  .topbar, .sidebar, .toc, .pager, .complete-bar, .sidebar-scrim { display: none !important; }
  body { background: #fff; color: #000; }
  .shell.has-sidebar { grid-template-columns: 1fr; }
}

/* ============================================================
   Accessibility layer — plain-language scaffolding
   Added so a reader with no mainframe background can follow.
   ============================================================ */

/* --- "In plain English" box --- */
.plain {
  margin: 1.5rem 0;
  padding: 1rem 1.15rem 1.05rem;
  border: 1px solid color-mix(in oklab, var(--brand-500) 32%, transparent);
  border-left: 3px solid var(--brand-500);
  border-radius: var(--radius-sm);
  background: color-mix(in oklab, var(--brand-500) 7%, var(--bg-elev));
}
.plain > .plain-label,
.analogy > .plain-label,
.compare > .plain-label {
  display: inline-flex; align-items: center; gap: .4rem;
  font-size: .68rem; font-weight: 750; letter-spacing: .1em; text-transform: uppercase;
  color: var(--brand-600); margin-bottom: .45rem;
}
html[data-theme="dark"] .plain > .plain-label { color: var(--brand-300); }
@media (prefers-color-scheme: dark) { html:not([data-theme="light"]) .plain > .plain-label { color: var(--brand-300); } }
.plain p, .analogy p, .compare p { margin: 0 0 .6rem; font-size: .95rem; }
.plain p:last-child, .analogy p:last-child, .compare p:last-child { margin-bottom: 0; }
.plain ul, .analogy ul, .compare ul { margin: .3rem 0 0; font-size: .93rem; }

/* --- "Picture it" analogy box --- */
.analogy {
  margin: 1.5rem 0; padding: 1rem 1.15rem 1.05rem;
  border: 1px solid color-mix(in oklab, var(--amber-500) 34%, transparent);
  border-left: 3px solid var(--amber-500);
  border-radius: var(--radius-sm);
  background: color-mix(in oklab, var(--amber-500) 8%, var(--bg-elev));
}
.analogy > .plain-label { color: var(--amber-600); }
html[data-theme="dark"] .analogy > .plain-label { color: var(--amber-300); }
@media (prefers-color-scheme: dark) { html:not([data-theme="light"]) .analogy > .plain-label { color: var(--amber-300); } }

/* --- "If you know X" comparison box --- */
.compare {
  margin: 1.5rem 0; padding: 1rem 1.15rem 1.05rem;
  border: 1px solid color-mix(in oklab, var(--sky-500) 32%, transparent);
  border-left: 3px solid var(--sky-500);
  border-radius: var(--radius-sm);
  background: color-mix(in oklab, var(--sky-500) 7%, var(--bg-elev));
}
.compare > .plain-label { color: var(--info); }

/* --- inline term with a hover/click definition --- */
button.term {
  font: inherit; color: inherit; background: none; padding: 0;
  border: 0; border-bottom: 1.5px dotted var(--accent);
  cursor: help; line-height: inherit; text-align: left;
}
button.term:hover { border-bottom-style: solid; color: var(--accent); }
button.term[aria-expanded="true"] { color: var(--accent); border-bottom-style: solid; }

.term-pop {
  position: absolute; z-index: 90; max-width: min(330px, 88vw);
  background: var(--bg-elev); color: var(--text);
  border: 1px solid var(--border-strong); border-radius: var(--radius-sm);
  box-shadow: var(--shadow-lg); padding: .7rem .85rem;
  font-size: .86rem; line-height: 1.55;
  opacity: 0; transform: translateY(-4px); pointer-events: none;
  transition: opacity .14s var(--ease), transform .14s var(--ease);
}
.term-pop[data-open="true"] { opacity: 1; transform: none; pointer-events: auto; }
.term-pop b { display: block; font-size: .74rem; text-transform: uppercase; letter-spacing: .07em;
  color: var(--accent); margin-bottom: .25rem; }
.term-pop .term-more { display: block; margin-top: .5rem; font-size: .78rem; color: var(--text-faint); }

/* --- vocabulary mapping table (primer) --- */
.vocab { display: grid; gap: .5rem; margin: 1.4rem 0; }
.vocab-row {
  display: grid; gap: .3rem .9rem; align-items: start;
  grid-template-columns: 1fr;
  padding: .7rem .9rem; border: 1px solid var(--border);
  border-radius: var(--radius-sm); background: var(--bg-elev);
}
@media (min-width: 700px) { .vocab-row { grid-template-columns: 190px 1fr; } }
.vocab-term { font-weight: 660; font-size: .93rem; }
.vocab-term small { display: block; font-weight: 500; font-size: .74rem; color: var(--text-faint); font-family: var(--font-mono); }
.vocab-plain { font-size: .92rem; color: var(--text-mute); }
.vocab-plain strong { color: var(--text); }

/* --- numbered concept steps --- */
.steps { list-style: none; padding: 0; margin: 1.3rem 0; display: grid; gap: .7rem; counter-reset: s; }
.steps > li {
  display: grid; grid-template-columns: 30px 1fr; gap: .8rem; align-items: start;
  padding: .8rem .95rem; border: 1px solid var(--border);
  border-radius: var(--radius-sm); background: var(--bg-elev);
  counter-increment: s;
}
.steps > li::before {
  content: counter(s);
  display: grid; place-items: center; width: 26px; height: 26px;
  border-radius: 50%; background: var(--accent-soft); color: var(--accent);
  font-family: var(--font-mono); font-size: .8rem; font-weight: 700;
  border: 1px solid color-mix(in oklab, var(--accent) 35%, transparent);
}
.steps b { display: block; margin-bottom: .15rem; }
.steps p { margin: 0; font-size: .9rem; color: var(--text-mute); }

/* --- two-column "wrong idea / right idea" --- */
.myth { display: grid; gap: .8rem; margin: 1.4rem 0; grid-template-columns: 1fr; }
@media (min-width: 760px) { .myth { grid-template-columns: 1fr 1fr; } }
.myth > div { padding: .9rem 1.05rem; border-radius: var(--radius-sm); border: 1px solid var(--border); }
.myth .no { background: var(--err-bg); border-color: color-mix(in oklab, var(--err) 30%, transparent); }
.myth .yes { background: var(--ok-bg); border-color: color-mix(in oklab, var(--ok) 30%, transparent); }
.myth h4 { margin: 0 0 .35rem; font-size: .8rem; text-transform: uppercase; letter-spacing: .06em; }
.myth .no h4 { color: var(--err); }
.myth .yes h4 { color: var(--ok); }
.myth p { margin: 0; font-size: .91rem; }

/* --- jargon key at the top of a module --- */
.jargon-key {
  margin: 1.4rem 0; padding: 0 1rem;
  border: 1px dashed var(--border-strong); border-radius: var(--radius);
  background: var(--bg-sunken);
}
.jargon-key > summary {
  cursor: pointer; padding: .85rem 0; font-weight: 640; font-size: .92rem;
  list-style: none; display: flex; align-items: center; gap: .5rem;
}
.jargon-key > summary::-webkit-details-marker { display: none; }
.jargon-key > summary::before { content: "▸"; color: var(--accent); display: inline-block; transition: transform .2s var(--ease); }
.jargon-key[open] > summary::before { transform: rotate(90deg); }
.jargon-key dl { margin: 0 0 1rem; display: grid; gap: .5rem; }
.jargon-key dt { font-weight: 650; font-size: .9rem; }
.jargon-key dd { margin: 0 0 .3rem; font-size: .89rem; color: var(--text-mute); }

/* ============================================================
   Diagram animation
   Reveal on scroll, stroke drawing, travelling flow pulses and
   stepped walkthroughs. All of it degrades to a plain static
   diagram under prefers-reduced-motion.
   ============================================================ */

figure.diagram { position: relative; }

/* --- fade-in reveal, staggered via --dgd set in JS --- */
figure.diagram svg [data-dg] {
  opacity: 0;
  transition: opacity .5s var(--ease);
  transition-delay: var(--dgd, 0s);
}
figure.diagram[data-dg-in="true"] svg [data-dg] { opacity: 1; }

/* --- connector lines draw themselves --- */
figure.diagram svg [data-dg-draw] {
  stroke-dasharray: var(--dglen);
  stroke-dashoffset: var(--dglen);
  transition: stroke-dashoffset .9s var(--ease), opacity .5s var(--ease);
  transition-delay: var(--dgd, 0s);
}
figure.diagram[data-dg-in="true"] svg [data-dg-draw] { stroke-dashoffset: 0; }

/* --- travelling pulse along a connector --- */
.dg-pulse { fill: var(--amber-400); }
html[data-theme="dark"] .dg-pulse { fill: var(--amber-300); }
@media (prefers-color-scheme: dark) {
  html:not([data-theme="light"]) .dg-pulse { fill: var(--amber-300); }
}
.dg-pulse-halo { fill: var(--amber-500); opacity: .22; }

/* --- stepped walkthrough highlighting --- */
figure.diagram svg .dg-el {
  transition: opacity .3s var(--ease), stroke .3s var(--ease),
              stroke-width .3s var(--ease), fill .3s var(--ease);
}
figure.diagram[data-dg-seq="running"] svg .dg-el { opacity: .25; }
figure.diagram svg .dg-el.dg-on { opacity: 1 !important; }
figure.diagram svg rect.dg-on {
  stroke: var(--amber-500);
  stroke-width: 2.4;
  fill: color-mix(in oklab, var(--amber-500) 16%, var(--bg-elev));
}
figure.diagram svg path.dg-on { stroke: var(--amber-500); stroke-width: 3; }
figure.diagram[data-dg-seq="running"] svg text { opacity: .35; transition: opacity .3s; }
figure.diagram[data-dg-seq="running"] svg text.dg-on { opacity: 1; }

/* --- controls + running caption --- */
.dg-controls {
  display: flex; flex-wrap: wrap; align-items: center; gap: .5rem;
  margin-top: .85rem; padding-top: .8rem; border-top: 1px solid var(--border-soft);
}
.dg-controls .btn { padding: .32rem .7rem; font-size: .8rem; }
.dg-step-count {
  font-family: var(--font-mono); font-size: .74rem; color: var(--text-faint);
  font-variant-numeric: tabular-nums;
}
.dg-say {
  margin-top: .7rem; padding: .7rem .9rem; min-height: 2.9rem;
  border: 1px solid color-mix(in oklab, var(--amber-500) 32%, transparent);
  border-left: 3px solid var(--amber-500);
  border-radius: var(--radius-sm);
  background: color-mix(in oklab, var(--amber-500) 8%, var(--bg-elev));
  font-size: .9rem; line-height: 1.5;
}
.dg-say:empty { display: none; }
.dg-say code {
  background: color-mix(in oklab, var(--amber-500) 14%, transparent);
  border-color: transparent;
}

/* --- animated bars used by the lab charts --- */
.bar-anim { transition: height .45s var(--ease), background-color .3s var(--ease); }

/* --- reduced motion: show everything, move nothing --- */
@media (prefers-reduced-motion: reduce) {
  figure.diagram svg [data-dg] { opacity: 1 !important; transition: none !important; }
  figure.diagram svg [data-dg-draw] { stroke-dashoffset: 0 !important; transition: none !important; }
  .dg-pulse, .dg-pulse-halo { display: none !important; }
  .bar-anim { transition: none !important; }
}