/* ===========================================================================
   style.css — chrome, layout, typography, content boxes, diagrams.

   No CDN, no build step, no framework. Two themes driven by one token block.
   Everything a chapter can contain is styled here; learn.css adds only the
   things the learning engine injects (quiz, toasts, notes, dashboards).

   Theme rule, and the reason it looks like this:
     :root                                   -> the complete LIGHT palette
     @media (prefers-color-scheme: dark)     -> dark, guarded so an explicit
       :root:not([data-theme="light"])          light choice still wins
     :root[data-theme="dark"]                -> the toggle wins in both ways
   No colour is defined ONLY inside a media query. site.js writes data-theme
   on <html> and flips the media attribute on the two theme-color metas.
   =========================================================================== */

:root {
  color-scheme: light;

  --bg:        #f6f7fb;
  --bg-soft:   #eceef6;
  --panel:     #ffffff;
  --panel-2:   #f9fafd;
  --ink:       #171a21;
  --ink-soft:  #4a5163;
  --ink-faint: #757d92;
  --line:      #dfe3ee;
  --line-soft: #ebeef6;

  --accent:      #2f5bd7;
  --accent-ink:  #1d3d9c;
  --accent-soft: #e6ecfd;

  --ok:      #16794a;
  --ok-soft: #e2f4ea;
  --warn:      #9a5b00;
  --warn-soft: #fdf0d9;
  --bad:      #b32133;
  --bad-soft: #fdeaec;
  --kid:      #0d6f74;
  --kid-soft: #e0f4f4;
  --pro:      #5b3ab8;
  --pro-soft: #eee9fc;

  --code-bg:   #f2f4fa;
  --code-ink:  #26303f;
  --code-line: #e2e6f0;
  /* Code colour (assets/highlight.js). One entry per KIND in the token
  dictionary, so the palette and the anatomy table classify a word the same
  way. Comments are dimmed on purpose: every line in this course carries one,
  which is right, and left at full strength it competes with the SQL. */
  --hl-com:  #6e7893;
  --hl-com-key: #5a6480;
  --hl-cl:   #17357f;
  --hl-kw:   #2b53c4;
  --hl-fn:   #6231b8;
  --hl-ty:   #0f6b42;
  --hl-str:  #0a6a70;
  --hl-num:  #8a5200;
  --hl-op:   #566079;
  --hl-opw:  #a8326d;
  --hl-id:   #7b5aa6;
  --hl-va:   #8a5200;
  --hl-key-bg:  rgba(47, 91, 215, .10);
  --hl-key-bar: #2f5bd7;

  --radius: 12px;
  --radius-sm: 8px;
  --shadow: 0 1px 2px rgba(18, 24, 40, .06), 0 8px 24px rgba(18, 24, 40, .06);
  --shadow-sm: 0 1px 2px rgba(18, 24, 40, .07);

  --sans: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --mono: ui-monospace, SFMono-Regular, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;

  --sidebar-w: 292px;
  --measure: 74ch;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    color-scheme: dark;
    --bg:        #101320;
    --bg-soft:   #161a2a;
    --panel:     #171b2a;
    --panel-2:   #1c2133;
    --ink:       #e7eaf3;
    --ink-soft:  #aeb6cc;
    --ink-faint: #7b849e;
    --line:      #2a3047;
    --line-soft: #232840;

    --accent:      #7d9bff;
    --accent-ink:  #a9bdff;
    --accent-soft: #1d2646;

    --ok:      #5fd39b;
    --ok-soft: #10281f;
    --warn:      #f0b45f;
    --warn-soft: #2e2413;
    --bad:      #ff8a97;
    --bad-soft: #331a1f;
    --kid:      #58cfd3;
    --kid-soft: #10292c;
    --pro:      #b39bff;
    --pro-soft: #211b3a;

    --code-bg:   #131826;
    --code-ink:  #d7deec;
    --code-line: #262c42;
    /* Code colour, dark. Same kinds, lifted off the darker --code-bg. */
    --hl-com:  #7f89a6;
    --hl-com-key: #9aa4bf;
    --hl-cl:   #9fb6ff;
    --hl-kw:   #7d9bff;
    --hl-fn:   #c0a6ff;
    --hl-ty:   #6ddfa8;
    --hl-str:  #5fd0d6;
    --hl-num:  #f0b45f;
    --hl-op:   #9aa4bd;
  --hl-opw:  #f2a0c8;
    --hl-id:   #c9a6e8;
    --hl-va:   #f0b45f;
    --hl-key-bg:  rgba(125, 155, 255, .15);
    --hl-key-bar: #7d9bff;

    --shadow: 0 1px 2px rgba(0, 0, 0, .4), 0 10px 28px rgba(0, 0, 0, .35);
    --shadow-sm: 0 1px 2px rgba(0, 0, 0, .4);
  }
}

:root[data-theme="dark"] {
  color-scheme: dark;
  --bg:        #101320;
  --bg-soft:   #161a2a;
  --panel:     #171b2a;
  --panel-2:   #1c2133;
  --ink:       #e7eaf3;
  --ink-soft:  #aeb6cc;
  --ink-faint: #7b849e;
  --line:      #2a3047;
  --line-soft: #232840;

  --accent:      #7d9bff;
  --accent-ink:  #a9bdff;
  --accent-soft: #1d2646;

  --ok:      #5fd39b;
  --ok-soft: #10281f;
  --warn:      #f0b45f;
  --warn-soft: #2e2413;
  --bad:      #ff8a97;
  --bad-soft: #331a1f;
  --kid:      #58cfd3;
  --kid-soft: #10292c;
  --pro:      #b39bff;
  --pro-soft: #211b3a;

  --code-bg:   #131826;
  --code-ink:  #d7deec;
  --code-line: #262c42;
  /* Code colour, dark. Same kinds, lifted off the darker --code-bg. */
  --hl-com:  #7f89a6;
  --hl-com-key: #9aa4bf;
  --hl-cl:   #9fb6ff;
  --hl-kw:   #7d9bff;
  --hl-fn:   #c0a6ff;
  --hl-ty:   #6ddfa8;
  --hl-str:  #5fd0d6;
  --hl-num:  #f0b45f;
  --hl-op:   #9aa4bd;
  --hl-opw:  #f2a0c8;
  --hl-id:   #c9a6e8;
  --hl-va:   #f0b45f;
  --hl-key-bg:  rgba(125, 155, 255, .15);
  --hl-key-bar: #7d9bff;

  --shadow: 0 1px 2px rgba(0, 0, 0, .4), 0 10px 28px rgba(0, 0, 0, .35);
  --shadow-sm: 0 1px 2px rgba(0, 0, 0, .4);
}

/* --------------------------------------------------------------- reset --- */

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

html { -webkit-text-size-adjust: 100%; scroll-behavior: smooth; }
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { animation-duration: .001ms !important; transition-duration: .001ms !important; }
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font: 16px/1.65 var(--sans);
  overflow-wrap: break-word;
}

a { color: var(--accent); text-decoration-thickness: 1px; text-underline-offset: 2px; }
a:hover { color: var(--accent-ink); }

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

img, svg { max-width: 100%; }

/* -------------------------------------------------------------- layout --- */

.layout { display: grid; grid-template-columns: var(--sidebar-w) minmax(0, 1fr); min-height: 100vh; }

/* The sidebar is position:fixed, so it is OUT of the grid flow and .main would
   otherwise fall into column 1 — underneath it. Column 1 exists only to
   reserve the width; the placement has to be explicit. */
.main {
  grid-column: 2;
  min-width: 0;
  padding: 84px clamp(18px, 4vw, 56px) 120px;
  margin: 0 auto;
  width: 100%;
  max-width: calc(var(--measure) + 12vw);
}
.main.wide { max-width: 1180px; }

/* ------------------------------------------------------------- top bar --- */

.topbar {
  position: fixed; inset: 0 0 auto 0; z-index: 40; height: 56px;
  display: flex; align-items: center; gap: 10px;
  padding: 0 14px 0 calc(var(--sidebar-w) + 14px);
  background: color-mix(in srgb, var(--bg) 86%, transparent);
  backdrop-filter: saturate(1.4) blur(10px);
  border-bottom: 1px solid var(--line);
}
.topbar .spacer { flex: 1 1 auto; }

.tb-btn {
  display: inline-flex; align-items: center; gap: 6px;
  height: 32px; padding: 0 11px;
  border: 1px solid var(--line); border-radius: 999px;
  background: var(--panel); color: var(--ink-soft);
  font: 500 13px/1 var(--sans); cursor: pointer; white-space: nowrap;
}
.tb-btn:hover { border-color: var(--accent); color: var(--accent); }
.tb-btn[aria-pressed="true"], .tb-btn.on {
  background: var(--accent-soft); border-color: var(--accent); color: var(--accent-ink);
}

.seg { display: inline-flex; border: 1px solid var(--line); border-radius: 999px; overflow: hidden; background: var(--panel); }
.seg button {
  border: 0; background: transparent; color: var(--ink-faint);
  font: 500 12.5px/1 var(--sans); padding: 8px 12px; cursor: pointer;
}
.seg button + button { border-left: 1px solid var(--line); }
.seg button[aria-pressed="true"] { background: var(--accent-soft); color: var(--accent-ink); }

.menu-btn { display: none; }

/* ------------------------------------------------------------- sidebar --- */

.sidebar {
  position: fixed; inset: 0 auto 0 0; width: var(--sidebar-w); z-index: 50;
  display: flex; flex-direction: column;
  background: var(--panel); border-right: 1px solid var(--line);
  overflow: hidden;
}

.brand {
  display: flex; align-items: center; gap: 10px;
  height: 56px; padding: 0 16px; flex: 0 0 auto;
  border-bottom: 1px solid var(--line-soft);
  color: var(--ink); text-decoration: none; font-weight: 700; letter-spacing: -.01em;
}
.brand .mark {
  width: 26px; height: 26px; border-radius: 7px; flex: 0 0 auto;
  background: linear-gradient(140deg, var(--accent), var(--kid));
  display: grid; place-items: center; color: #fff; font: 700 13px/1 var(--mono);
}
.brand small { display: block; font: 400 11px/1.2 var(--sans); color: var(--ink-faint); letter-spacing: 0; }

.sb-search { padding: 10px 12px; flex: 0 0 auto; border-bottom: 1px solid var(--line-soft); }
.sb-search input {
  width: 100%; height: 34px; padding: 0 10px;
  border: 1px solid var(--line); border-radius: var(--radius-sm);
  background: var(--panel-2); color: var(--ink); font: 13px var(--sans);
}
.sb-search input::placeholder { color: var(--ink-faint); }

.sb-scroll { flex: 1 1 auto; overflow-y: auto; padding: 8px 8px 24px; scrollbar-width: thin; }

.sb-part {
  margin: 14px 8px 6px; font: 600 10.5px/1 var(--sans);
  letter-spacing: .09em; text-transform: uppercase; color: var(--ink-faint);
  display: flex; align-items: center; gap: 8px;
}
.sb-part .bar { flex: 1 1 auto; height: 4px; border-radius: 3px; background: var(--line-soft); overflow: hidden; }
.sb-part .bar i { display: block; height: 100%; background: var(--accent); width: 0; }

.sb-link {
  display: flex; align-items: baseline; gap: 8px;
  padding: 6px 10px; border-radius: var(--radius-sm);
  color: var(--ink-soft); text-decoration: none; font-size: 13.5px; line-height: 1.35;
}
.sb-link:hover { background: var(--bg-soft); color: var(--ink); }
.sb-link.active { background: var(--accent-soft); color: var(--accent-ink); font-weight: 600; }
.sb-link .num { font: 600 11px/1.6 var(--mono); color: var(--ink-faint); flex: 0 0 22px; }
.sb-link.active .num { color: var(--accent); }
.sb-link .mark { margin-left: auto; font-size: 11px; flex: 0 0 auto; }
.sb-empty { padding: 18px 12px; color: var(--ink-faint); font-size: 13px; }

/* --------------------------------------------------------- prose scale --- */

.crumbs { margin: 0 0 6px; font: 500 12.5px/1.5 var(--sans); color: var(--ink-faint); }
.crumbs span { opacity: .55; margin: 0 6px; }

h1 { font-size: clamp(28px, 4.2vw, 40px); line-height: 1.16; letter-spacing: -.022em; margin: 0 0 12px; }
h2 {
  font-size: clamp(21px, 2.6vw, 26px); line-height: 1.28; letter-spacing: -.014em;
  margin: 46px 0 12px; padding-top: 14px; border-top: 1px solid var(--line-soft); scroll-margin-top: 76px;
}
h3 { font-size: 17.5px; line-height: 1.35; margin: 28px 0 8px; letter-spacing: -.008em; }
h4 { font-size: 15px; margin: 20px 0 6px; color: var(--ink-soft); }

p { margin: 0 0 15px; max-width: var(--measure); }
.lede { font-size: 18.5px; line-height: 1.6; color: var(--ink-soft); margin-bottom: 22px; max-width: var(--measure); }

ul, ol { max-width: var(--measure); padding-left: 22px; margin: 0 0 15px; }
li { margin: 5px 0; }
li > ul, li > ol { margin: 5px 0; }

hr { border: 0; border-top: 1px solid var(--line); margin: 34px 0; }

blockquote {
  margin: 18px 0; padding: 2px 0 2px 16px;
  border-left: 3px solid var(--line); color: var(--ink-soft); max-width: var(--measure);
}

strong { font-weight: 650; color: var(--ink); }

/* --------------------------------------------------------------- code --- */

code {
  font: 0.885em/1.5 var(--mono);
  background: var(--code-bg); color: var(--code-ink);
  border: 1px solid var(--code-line); border-radius: 5px; padding: .1em .32em;
}

pre {
  position: relative;
  margin: 16px 0; padding: 14px 16px;
  background: var(--code-bg); border: 1px solid var(--code-line);
  border-radius: var(--radius); overflow-x: auto;
  font: 13.5px/1.62 var(--mono); color: var(--code-ink);
  -webkit-overflow-scrolling: touch;
}
pre code { background: none; border: 0; padding: 0; font-size: inherit; color: inherit; }

.copy-btn {
  position: absolute; top: 8px; right: 8px;
  border: 1px solid var(--line); border-radius: 6px;
  background: var(--panel); color: var(--ink-faint);
  font: 500 11px/1 var(--sans); padding: 5px 8px; cursor: pointer; opacity: 0;
  transition: opacity .12s ease;
}
pre:hover .copy-btn, .copy-btn:focus-visible { opacity: 1; }
.copy-btn.done { color: var(--ok); border-color: var(--ok); }

/* -------------------------------------------------------------- tables --- */

.table-wrap { overflow-x: auto; margin: 18px 0; border: 1px solid var(--line); border-radius: var(--radius); }
table { border-collapse: collapse; width: 100%; font-size: 14px; }
th, td { text-align: left; padding: 9px 13px; border-bottom: 1px solid var(--line-soft); vertical-align: top; }
thead th { background: var(--panel-2); font-weight: 650; font-size: 12.5px; letter-spacing: .01em; white-space: nowrap; }
tbody tr:last-child td { border-bottom: 0; }
td code, th code { white-space: nowrap; }

/* --------------------------------------------------------------- boxes --- */

.box {
  margin: 18px 0; padding: 14px 16px;
  border: 1px solid var(--line); border-left: 3px solid var(--ink-faint);
  border-radius: var(--radius); background: var(--panel);
  max-width: var(--measure);
}
.box > :last-child { margin-bottom: 0; }
.box-title { font: 650 12px/1.4 var(--sans); letter-spacing: .05em; text-transform: uppercase; margin-bottom: 7px; }

.box.kid  { border-left-color: var(--kid);  background: var(--kid-soft);  }
.box.kid  .box-title { color: var(--kid); }
.box.pro  { border-left-color: var(--pro);  background: var(--pro-soft);  }
.box.pro  .box-title { color: var(--pro); }
.box.trap { border-left-color: var(--bad);  background: var(--bad-soft);  }
.box.trap .box-title { color: var(--bad); }
.box.note { border-left-color: var(--accent); background: var(--accent-soft); }
.box.note .box-title { color: var(--accent-ink); }
.box.good { border-left-color: var(--ok); background: var(--ok-soft); }
.box.good .box-title { color: var(--ok); }

/* The Both / Simple / Pro switch. site.js writes data-explain on <html>. */
html[data-explain="kid"] .box.pro { display: none; }
html[data-explain="pro"] .box.kid { display: none; }

.tryit {
  margin: 18px 0; padding: 14px 16px; max-width: var(--measure);
  border: 1px dashed var(--accent); border-radius: var(--radius);
  background: color-mix(in srgb, var(--accent-soft) 60%, transparent);
}
.tryit::before {
  content: "⌨ Try it"; display: block;
  font: 650 12px/1.4 var(--sans); letter-spacing: .05em; text-transform: uppercase;
  color: var(--accent-ink); margin-bottom: 7px;
}
.tryit > :last-child { margin-bottom: 0; }

.rules {
  margin: 26px 0; padding: 16px 18px; max-width: var(--measure);
  border: 1px solid var(--line); border-radius: var(--radius);
  background: linear-gradient(180deg, var(--panel-2), var(--panel));
  box-shadow: var(--shadow-sm);
}
.rules::before {
  content: "★ Golden rules"; display: block;
  font: 650 12px/1.4 var(--sans); letter-spacing: .05em; text-transform: uppercase;
  color: var(--warn); margin-bottom: 9px;
}
.rules ol { margin: 0; padding-left: 20px; }
.rules li { margin: 7px 0; }

.qa {
  margin: 14px 0; padding: 13px 16px; max-width: var(--measure);
  border: 1px solid var(--line); border-radius: var(--radius); background: var(--panel);
}
.qa .q { font-weight: 650; margin: 0 0 6px; }
.qa .q::before { content: "Q "; color: var(--accent); font-family: var(--mono); }
.qa .a { margin: 0; color: var(--ink-soft); }
.qa .a::before { content: "A "; color: var(--ok); font-family: var(--mono); font-weight: 700; }

.kbd {
  display: inline-block; padding: 1px 6px; border: 1px solid var(--line);
  border-bottom-width: 2px; border-radius: 5px; background: var(--panel-2);
  font: 600 11.5px/1.6 var(--mono); color: var(--ink-soft);
}

/* ----------------------------------------------------------------- toc --- */

nav#toc {
  margin: 22px 0 30px; padding: 12px 16px; max-width: var(--measure);
  border: 1px solid var(--line); border-radius: var(--radius); background: var(--panel);
}
nav#toc b { display: block; font: 650 11px/1.4 var(--sans); letter-spacing: .07em; text-transform: uppercase; color: var(--ink-faint); margin-bottom: 7px; }
nav#toc ol { margin: 0; padding-left: 19px; }
nav#toc li { margin: 3px 0; }
nav#toc a { color: var(--ink-soft); text-decoration: none; font-size: 14px; }
nav#toc a:hover { color: var(--accent); text-decoration: underline; }

/* --------------------------------------------------------------- pager --- */

#pager { display: grid; grid-template-columns: 1fr 1fr; gap: 12px; margin-top: 54px; }
#pager a {
  display: block; padding: 13px 16px; text-decoration: none;
  border: 1px solid var(--line); border-radius: var(--radius);
  background: var(--panel); color: var(--ink);
}
#pager a:hover { border-color: var(--accent); }
#pager a span { display: block; font: 600 11px/1.4 var(--sans); letter-spacing: .06em; text-transform: uppercase; color: var(--ink-faint); margin-bottom: 3px; }
#pager a.next { text-align: right; }
#pager a.prev + a.next:only-of-type { grid-column: 2; }

/* ------------------------------------------------------------ diagrams --- */

figure.diagram {
  margin: 24px 0; padding: 14px; overflow-x: auto;
  border: 1px solid var(--line); border-radius: var(--radius); background: var(--panel);
}
figure.diagram svg { display: block; width: 100%; height: auto; min-width: 520px; }
figure.diagram figcaption { margin-top: 9px; font-size: 13px; color: var(--ink-faint); text-align: center; }

/* Diagram tokens — inline SVG uses these classes so it follows the theme. */
.d-box   { fill: var(--panel-2); stroke: var(--line); stroke-width: 1.5; }
.d-box-a { fill: var(--accent-soft); stroke: var(--accent); stroke-width: 1.5; }
.d-box-k { fill: var(--kid-soft); stroke: var(--kid); stroke-width: 1.5; }
.d-box-p { fill: var(--pro-soft); stroke: var(--pro); stroke-width: 1.5; }
.d-box-g { fill: var(--ok-soft); stroke: var(--ok); stroke-width: 1.5; }
.d-box-b { fill: var(--bad-soft); stroke: var(--bad); stroke-width: 1.5; }
.d-box-w { fill: var(--warn-soft); stroke: var(--warn); stroke-width: 1.5; }
.d-line  { stroke: var(--ink-faint); stroke-width: 1.5; fill: none; }
.d-line-a{ stroke: var(--accent); stroke-width: 1.8; fill: none; }
.d-line-b{ stroke: var(--bad); stroke-width: 1.8; fill: none; stroke-dasharray: 5 4; }
.d-fill  { fill: var(--ink-faint); }
.d-fill-a{ fill: var(--accent); }
.d-t     { fill: var(--ink); font: 13px var(--sans); }
.d-t-s   { fill: var(--ink-soft); font: 11.5px var(--sans); }
.d-t-m   { fill: var(--code-ink); font: 12px var(--mono); }
.d-t-b   { fill: var(--ink); font: 650 13px var(--sans); }
.d-t-c   { fill: var(--ink-faint); font: 10.5px var(--sans); letter-spacing: .06em; }

/* -------------------------------------------------------------- cards --- */

.cards { display: grid; grid-template-columns: repeat(auto-fill, minmax(258px, 1fr)); gap: 13px; margin: 18px 0 30px; }
.card {
  display: block; padding: 14px 15px; text-decoration: none;
  border: 1px solid var(--line); border-radius: var(--radius);
  background: var(--panel); color: var(--ink); box-shadow: var(--shadow-sm);
}
.card:hover { border-color: var(--accent); transform: translateY(-1px); }
.card .n { font: 600 11px/1 var(--mono); color: var(--ink-faint); letter-spacing: .04em; }
.card h3 { margin: 6px 0 5px; font-size: 15.5px; line-height: 1.32; }
.card p { margin: 0; font-size: 13px; color: var(--ink-soft); line-height: 1.5; }
.card .foot { margin-top: 9px; display: flex; align-items: center; gap: 7px; font-size: 11.5px; color: var(--ink-faint); }

.pill {
  display: inline-flex; align-items: center; gap: 5px;
  padding: 2px 9px; border-radius: 999px; font: 600 11px/1.7 var(--sans);
  background: var(--bg-soft); color: var(--ink-soft); border: 1px solid var(--line);
}
.pill.req  { background: var(--accent-soft); color: var(--accent-ink); border-color: transparent; }
.pill.extra{ background: var(--warn-soft); color: var(--warn); border-color: transparent; }
.pill.ok   { background: var(--ok-soft); color: var(--ok); border-color: transparent; }
.pill.bad  { background: var(--bad-soft); color: var(--bad); border-color: transparent; }

/* --------------------------------------------------------------- misc --- */

.hero {
  padding: 26px 26px 24px; margin: 0 0 26px;
  border: 1px solid var(--line); border-radius: 16px;
  background:
    radial-gradient(1100px 260px at 8% -30%, var(--accent-soft), transparent 70%),
    linear-gradient(180deg, var(--panel), var(--panel-2));
  box-shadow: var(--shadow);
}
.hero h1 { margin-bottom: 10px; }
.hero .lede { margin-bottom: 16px; }
.row { display: flex; flex-wrap: wrap; gap: 9px; align-items: center; }

.btn {
  display: inline-flex; align-items: center; gap: 7px;
  padding: 9px 15px; border-radius: 999px; border: 1px solid var(--accent);
  background: var(--accent); color: #fff; text-decoration: none;
  font: 600 13.5px/1 var(--sans); cursor: pointer;
}
.btn:hover { filter: brightness(1.06); color: #fff; }
.btn.ghost { background: var(--panel); color: var(--accent); }
.btn.ghost:hover { background: var(--accent-soft); color: var(--accent-ink); }
.btn.quiet { background: var(--panel); color: var(--ink-soft); border-color: var(--line); }
.btn.quiet:hover { border-color: var(--accent); color: var(--accent); }
.btn[disabled] { opacity: .5; cursor: not-allowed; filter: none; }

.muted { color: var(--ink-faint); }
.small { font-size: 13px; }
.mono  { font-family: var(--mono); }
.center { text-align: center; }
.stack > * + * { margin-top: 12px; }

.panel {
  padding: 16px 18px; border: 1px solid var(--line);
  border-radius: var(--radius); background: var(--panel); box-shadow: var(--shadow-sm);
}
.panel > :last-child { margin-bottom: 0; }
.panel h2 { margin-top: 0; border-top: 0; padding-top: 0; }

.grid-2 { display: grid; grid-template-columns: repeat(auto-fit, minmax(300px, 1fr)); gap: 14px; }
.grid-3 { display: grid; grid-template-columns: repeat(auto-fit, minmax(210px, 1fr)); gap: 12px; }

.skip {
  position: absolute; left: -9999px; top: 0; z-index: 100;
  background: var(--accent); color: #fff; padding: 10px 16px; border-radius: 0 0 8px 0;
}
.skip:focus { left: 0; color: #fff; }

.sr-only {
  position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; border: 0;
}

/* --------------------------------------------------------- responsive --- */

@media (max-width: 1000px) {
  .layout { grid-template-columns: 1fr; }
  .main { grid-column: 1; }
  .topbar { padding-left: 14px; }
  .menu-btn { display: inline-flex; }
  .sidebar {
    transform: translateX(-100%); transition: transform .18s ease;
    box-shadow: var(--shadow); width: min(320px, 86vw);
  }
  body.nav-open .sidebar { transform: none; }
  body.nav-open::after {
    content: ""; position: fixed; inset: 0; z-index: 45; background: rgba(8, 10, 20, .42);
  }
  .main { padding-top: 76px; }
  #pager { grid-template-columns: 1fr; }
}

@media print {
  .topbar, .sidebar, #pager, .copy-btn, .quiz, .lf-toast { display: none !important; }
  .layout { display: block; }
  .main { padding: 0; max-width: none; }
  body { background: #fff; color: #000; }
}

/* ============================================================ code examples ===
   figure.codex — the annotated example. The <pre> inside it is an ordinary
   code block; everything else on the figure is the apparatus that makes the
   example teachable: a caption saying what it is for, hand-written conversion
   notes, and the anatomy table generated by assets/codex.js.

   The whole figure is one card so it reads as one object, and so a reader
   scrolling past a chapter can see where an example starts and stops.        */

figure.codex {
  margin: 22px 0; padding: 0;
  border: 1px solid var(--line); border-radius: var(--radius);
  background: var(--panel); overflow: hidden;
}
figure.codex > figcaption {
  padding: 10px 15px; border-bottom: 1px solid var(--line-soft);
  background: var(--panel-2);
  font: 600 13px/1.45 var(--sans); color: var(--ink-soft);
}
figure.codex > figcaption b, figure.codex > figcaption strong { color: var(--ink); }
figure.codex > pre {
  margin: 0; border: 0; border-radius: 0; background: var(--code-bg);
}

/* --------------------------------------------------- code colour and focus
   Rendered by assets/highlight.js, which wraps existing characters in spans
   and never adds or removes one. The classes mirror the KINDS in
   assets/syntax.js, so a token that the anatomy table calls a clause is the
   token this palette paints as a clause. */

.hl-com { color: var(--hl-com); font-style: italic; }
.hl-cl  { color: var(--hl-cl);  font-weight: 600; }
.hl-kw  { color: var(--hl-kw); }
.hl-fn  { color: var(--hl-fn); }
.hl-ty  { color: var(--hl-ty); }
.hl-str { color: var(--hl-str); }
.hl-num { color: var(--hl-num); }
.hl-op  { color: var(--hl-op); }
.hl-opw { color: var(--hl-opw); }
.hl-id  { color: var(--hl-id); }
.hl-va  { color: var(--hl-va); }
/* Literals, hints, directives and tool names are rare enough that a shade of
   their own would be noise rather than information. */
.hl-li, .hl-hi, .hl-di, .hl-to { color: var(--hl-kw); }

/*  display:inline is LOAD-BEARING, not a default being restated. The newline
    between two line spans is a text node outside them; make these blocks and
    the newline renders twice, and code.innerText — what the copy button
    hands the reader — gains a blank line between every line of SQL. */
.hl-ln { display: inline; }

/*  The line that carries the lesson. The negative margin exactly cancels the
    bar plus the padding, so the line does NOT shift right: these examples
    align their trailing comments into a column, and nudging one line out of
    that column to emphasise it would cost more than the emphasis is worth. */
.hl-key {
  border-left: 3px solid var(--hl-key-bar);
  background: var(--hl-key-bg);
  margin-left: -9px;
  padding-left: 6px;
  padding-right: 5px;
  border-radius: 0 4px 4px 0;
}
/* On the focus line the comment is part of the point, so it is dimmed less. */
.hl-key .hl-com { color: var(--hl-com-key); }

@media print {
  .hl-key { background: none; border-left: 3px solid #666; }
}

/* Hand-written notes: the conversions and type surprises specific to THIS
   example, which no generated table can know about. */
.cx-conv {
  padding: 11px 15px; border-top: 1px solid var(--line-soft);
  background: var(--panel); font-size: 13.5px; color: var(--ink-soft);
}
.cx-conv b { display: block; margin-bottom: 5px; color: var(--ink); font-size: 12px;
  letter-spacing: .05em; text-transform: uppercase; }
.cx-conv ul { margin: 0; padding-left: 19px; }
.cx-conv li { margin: 4px 0; }

/* The bar under the code: what language, how many lines, and the run link. */
.cx-bar {
  display: flex; align-items: center; gap: 10px; flex-wrap: wrap;
  padding: 7px 15px; border-top: 1px solid var(--line-soft); background: var(--panel-2);
}
.cx-meta { font: 500 11.5px/1.4 var(--mono); color: var(--ink-faint); }
.cx-grow { flex: 1 1 auto; }
.cx-run {
  font: 600 12px/1 var(--sans); text-decoration: none;
  border: 1px solid var(--accent); color: var(--accent-ink);
  background: var(--accent-soft); border-radius: 6px; padding: 6px 10px;
}
.cx-run:hover { background: var(--accent); color: #fff; }

/* The generated anatomy. Closed by default; the reader's choice is remembered. */
.cx-anatomy { border-top: 1px solid var(--line-soft); background: var(--panel); }
.cx-anatomy > summary {
  display: flex; align-items: center; gap: 10px; cursor: pointer;
  padding: 9px 15px; font: 600 12.5px/1.4 var(--sans); color: var(--ink-soft);
  list-style: none;
}
.cx-anatomy > summary::-webkit-details-marker { display: none; }
.cx-anatomy > summary::before {
  content: "▸"; color: var(--ink-faint); font-size: 11px; transition: transform .12s ease;
}
.cx-anatomy[open] > summary::before { content: "▾"; }
.cx-anatomy > summary:hover { color: var(--accent); }
.cx-sum-n { font: 500 11.5px var(--mono); color: var(--ink-faint); margin-left: auto; }

.cx-flow { padding: 4px 15px 10px; font-size: 13px; color: var(--ink-soft); }
.cx-flow b { display: block; font-size: 12px; letter-spacing: .04em;
  text-transform: uppercase; color: var(--ink-faint); margin-bottom: 5px; }
.cx-flow ol { margin: 0; padding-left: 20px; }
.cx-flow li { margin: 3px 0; }
.cx-flow code { font-size: .85em; }

.cx-anatomy .table-wrap { margin: 0; border: 0; border-top: 1px solid var(--line-soft);
  border-radius: 0; }
.cx-table { font-size: 13px; }
.cx-table td:first-child code { white-space: nowrap; font-weight: 600; }
.cx-table .cx-types { color: var(--ink-soft); }
.cx-kind {
  display: inline-block; font: 600 10.5px/1.5 var(--sans); letter-spacing: .04em;
  text-transform: uppercase; padding: 1px 6px; border-radius: 999px;
  border: 1px solid var(--line); background: var(--panel-2); color: var(--ink-faint);
}
.cx-k-clause   { border-color: var(--accent); color: var(--accent-ink); background: var(--accent-soft); }
.cx-k-function { border-color: var(--pro); color: var(--pro); background: var(--pro-soft); }
.cx-k-type     { border-color: var(--ok); color: var(--ok); background: var(--ok-soft); }
.cx-k-operator { border-color: var(--warn); color: var(--warn); background: var(--warn-soft); }
.cx-dial {
  display: block; margin-top: 3px; font: 500 11px var(--mono); color: var(--ink-faint);
}

@media (max-width: 700px) {
  .cx-table { font-size: 12.5px; }
  figure.codex > figcaption { font-size: 12.5px; }
}

/* ---------------------------------------------------------------- free-course framing
   Landing page only. The same four assurances the hub makes, repeated here because most
   visitors arrive from a search engine straight into a course and never see the hub.

   Every colour is a token this stylesheet already defines, so each subject keeps its own
   brand. The two-level fallbacks are for the SQL course, whose palette names the accent
   --accent rather than --brand; var(--brand, var(--accent)) resolves correctly in both
   without a second copy of this block.
   ------------------------------------------------------------------------------------ */
.free-strip {
  display: flex; flex-wrap: wrap; align-items: center; gap: 10px 18px;
  margin: 18px 0 24px; padding: 13px 16px;
  background: var(--panel); border: 1px solid var(--line);
  border-radius: var(--radius);
}
.free-badge {
  font-size: 11.5px; font-weight: 700; letter-spacing: .06em; text-transform: uppercase;
  padding: 4px 10px; border-radius: 999px;
  background: var(--brand-soft, var(--accent-soft));
  color: var(--brand-ink, var(--accent-ink));
  border: 1px solid var(--brand, var(--accent));
}
.free-item {
  display: inline-flex; align-items: center; gap: 7px;
  font-size: 14px; color: var(--ink-soft);
}
.free-item svg { color: var(--pro); flex: none; }
.free-hub {
  margin-left: auto; font-size: 13.5px; font-weight: 600; white-space: nowrap;
  color: var(--brand-ink, var(--accent-ink)); text-decoration: none;
}
.free-hub:hover { text-decoration: underline; }
@media (max-width: 680px) {
  .free-hub { margin-left: 0; }
}