/* The Harness — instrument-panel theme. Shared by every page. */
:root {
  --void: #05070a;
  --panel: #0b1016;
  --panel-2: #101822;
  --rule: #1c2833;
  --rule-hi: #2a3b4a;
  --text: #d8e3ea;
  --text-dim: #8a9aa8;
  --text-faint: #7a8b9c; /* ≥5:1 on every panel (WCAG AA) */
  --cyan: #3ee6ff;
  --cyan-dim: #1b8fa3;
  --amber: #ffb347;
  --red: #ff5d6c;
  --green: #6be3a0;
  --violet: #a88bff;
  --glow: 0 0 24px rgba(62, 230, 255, .18);
  --serif: "Source Serif 4", Georgia, serif;
  --sans: "Space Grotesk", system-ui, sans-serif;
  --mono: "JetBrains Mono", ui-monospace, monospace;
  --measure: 68ch;
  color-scheme: dark;
}

*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; -webkit-text-size-adjust: 100%; }
body {
  margin: 0;
  background: var(--void);
  color: var(--text);
  font: 400 18px/1.7 var(--serif);
  overflow-x: hidden;
}
/* faint scan grid behind everything */
body::before {
  content: ""; position: fixed; inset: 0; z-index: -1; pointer-events: none;
  background-image:
    linear-gradient(rgba(62,230,255,.035) 1px, transparent 1px),
    linear-gradient(90deg, rgba(62,230,255,.035) 1px, transparent 1px);
  background-size: 48px 48px;
  mask-image: radial-gradient(ellipse at 50% 0%, #000 30%, transparent 80%);
}
a { color: var(--cyan); text-decoration-color: rgba(62,230,255,.35); text-underline-offset: 3px; }
a:hover { text-decoration-color: var(--cyan); }
:focus-visible { outline: 2px solid var(--cyan); outline-offset: 3px; border-radius: 2px; }
::selection { background: rgba(62,230,255,.3); color: #fff; }
img, svg, canvas { max-width: 100%; }

/* ---------- top bar ---------- */
.hud {
  position: sticky; top: 0; z-index: 50;
  display: flex; align-items: center; gap: 20px;
  padding: 12px clamp(16px, 4vw, 40px);
  background: rgba(5,7,10,.82); backdrop-filter: blur(10px);
  border-bottom: 1px solid var(--rule);
  font: 500 13px/1 var(--mono); letter-spacing: .04em;
}
.hud a { color: var(--text-dim); text-decoration: none; }
.hud a:hover, .hud a[aria-current="page"] { color: var(--cyan); }
.hud .mark { color: var(--text); font-weight: 600; display: flex; align-items: center; gap: 10px; }
.hud .mark i { width: 8px; height: 8px; border-radius: 50%; background: var(--green); box-shadow: 0 0 10px var(--green); animation: pulse 2.4s infinite; }
.hud nav { margin-left: auto; display: flex; gap: 22px; }
.hud-meter { position: absolute; left: 0; bottom: -1px; height: 2px; width: 0; background: linear-gradient(90deg, var(--cyan), var(--violet)); box-shadow: var(--glow); }
@keyframes pulse { 50% { opacity: .35; } }
@media (max-width: 640px) { .hud nav { gap: 14px; } .hud nav .opt { display: none; } }

/* ---------- layout ---------- */
.wrap { max-width: 1180px; margin: 0 auto; padding: 0 clamp(16px, 4vw, 40px); }
.prose { max-width: var(--measure); }
.eyebrow { font: 500 12px/1 var(--mono); letter-spacing: .18em; text-transform: uppercase; color: var(--cyan); }
h1, h2, h3, h4 { font-family: var(--sans); font-weight: 600; letter-spacing: -.02em; line-height: 1.15; color: #fff; }
h1 { font-size: clamp(40px, 7vw, 84px); margin: .2em 0 .3em; }
h2 { font-size: clamp(26px, 3.4vw, 38px); margin: 2.4em 0 .6em; }
h3 { font-size: 22px; margin: 1.8em 0 .5em; }
p { margin: 0 0 1.15em; }
strong { color: #fff; font-weight: 600; }
code, kbd { font: 500 .86em/1 var(--mono); background: var(--panel-2); border: 1px solid var(--rule); border-radius: 4px; padding: .15em .4em; color: var(--cyan); }
pre { font: 13.5px/1.6 var(--mono); background: var(--panel); border: 1px solid var(--rule); border-radius: 8px; padding: 16px 18px; overflow-x: auto; color: var(--text); }
pre code { background: none; border: 0; padding: 0; color: inherit; }
hr { border: 0; border-top: 1px solid var(--rule); margin: 3em 0; }
.dim { color: var(--text-dim); }
.mono { font-family: var(--mono); }

/* ---------- chapter page ---------- */
.ch-hero { padding: clamp(56px, 10vw, 120px) 0 40px; border-bottom: 1px solid var(--rule); position: relative; }
.ch-hero .num { font: 600 clamp(80px, 16vw, 200px)/.8 var(--sans); color: transparent; -webkit-text-stroke: 1px rgba(62,230,255,.28); position: absolute; right: 0; top: 40px; user-select: none; }
.ch-hero h1 { max-width: calc(100% - 230px); }
@media (max-width: 640px) { .ch-hero h1 { max-width: none; } }
.ch-hero .dek { font-size: clamp(19px, 2.2vw, 24px); color: var(--text-dim); max-width: 46ch; }
.ch-meta { display: flex; flex-wrap: wrap; gap: 8px 24px; margin-top: 28px; font: 12px/1 var(--mono); color: var(--text-faint); letter-spacing: .06em; }
.ch-body { display: grid; grid-template-columns: minmax(0, 1fr) 220px; gap: 56px; padding: 48px 0 96px; }
.ch-body > article { min-width: 0; }
@media (max-width: 980px) { .ch-body { grid-template-columns: 1fr; } .rail { display: none; } }
.rail { position: sticky; top: 76px; align-self: start; font: 12.5px/1.5 var(--mono); }
.rail ol { list-style: none; margin: 0; padding: 0; border-left: 1px solid var(--rule); }
.rail li a { display: block; padding: 6px 0 6px 14px; color: var(--text-faint); text-decoration: none; margin-left: -1px; border-left: 1px solid transparent; }
.rail li a.on { color: var(--cyan); border-left-color: var(--cyan); }
.rail .label { color: var(--text-faint); letter-spacing: .14em; text-transform: uppercase; font-size: 11px; margin-bottom: 10px; }

/* drop cap on first paragraph */
.lede::first-letter { float: left; font: 600 4.2em/.85 var(--sans); color: var(--cyan); margin: .08em .12em 0 0; text-shadow: var(--glow); }

/* citations */
sup.cite a { font: 600 11px/1 var(--mono); color: var(--cyan); text-decoration: none; padding: 0 2px; }
sup.cite a:hover { background: rgba(62,230,255,.12); border-radius: 3px; }
.refs { font-size: 14.5px; line-height: 1.55; color: var(--text-dim); padding-left: 1.6em; }
.refs li { margin-bottom: .6em; }
.refs li:target { color: #fff; background: rgba(62,230,255,.07); }
.refs a { word-break: break-word; }

/* pull quote */
.pull { margin: 2.2em 0; padding: 6px 0 6px 24px; border-left: 2px solid var(--cyan); font: 500 clamp(21px, 2.4vw, 26px)/1.4 var(--sans); color: #fff; letter-spacing: -.01em; }
.pull cite { display: block; margin-top: 10px; font: 400 13px/1.4 var(--mono); color: var(--text-faint); font-style: normal; }

/* callout */
.note { margin: 2em 0; padding: 18px 20px; background: var(--panel); border: 1px solid var(--rule); border-left: 3px solid var(--amber); border-radius: 6px; font-size: 16px; }
.note b { font: 600 12px/1 var(--mono); letter-spacing: .14em; color: var(--amber); display: block; margin-bottom: 8px; text-transform: uppercase; }

/* data table */
.tbl { width: 100%; border-collapse: collapse; margin: 1.6em 0; font: 14px/1.45 var(--mono); }
.tbl th { text-align: left; font-weight: 500; color: var(--text-faint); letter-spacing: .06em; border-bottom: 1px solid var(--rule-hi); padding: 8px 10px; }
.tbl td { border-bottom: 1px solid var(--rule); padding: 8px 10px; vertical-align: top; }
.tbl td.n { text-align: right; color: var(--cyan); }
.tbl-scroll { overflow-x: auto; }

/* ---------- instrument (interactive simulation) ---------- */
.instrument {
  margin: 2.6em 0; border: 1px solid var(--rule-hi); border-radius: 12px; overflow: hidden;
  background: linear-gradient(180deg, var(--panel-2), var(--panel));
  box-shadow: var(--glow), inset 0 1px 0 rgba(255,255,255,.03);
  font-family: var(--mono);
}
.instrument > header { display: flex; align-items: center; gap: 12px; padding: 12px 16px; border-bottom: 1px solid var(--rule); font: 500 12px/1 var(--mono); letter-spacing: .12em; text-transform: uppercase; color: var(--text-dim); }
.instrument > header::before { content: ""; width: 7px; height: 7px; border-radius: 50%; background: var(--cyan); box-shadow: 0 0 8px var(--cyan); }
.instrument > header .tag { margin-left: auto; color: var(--text-faint); letter-spacing: .06em; text-transform: none; }
.instrument .body { padding: 20px 18px; font-size: 13.5px; line-height: 1.5; }
.instrument .caption { padding: 12px 18px; border-top: 1px solid var(--rule); font: 13px/1.5 var(--mono); color: var(--text-faint); }
.instrument label { color: var(--text-dim); }
.instrument .readout { font: 600 clamp(28px, 4vw, 44px)/1 var(--sans); color: var(--cyan); text-shadow: var(--glow); font-variant-numeric: tabular-nums; }
.instrument .readout.bad { color: var(--amber); text-shadow: 0 0 24px rgba(255,179,71,.25); }
.instrument .readout.fail { color: var(--red); text-shadow: 0 0 24px rgba(255,93,108,.25); }
.instrument .readout.ok { color: var(--green); text-shadow: 0 0 24px rgba(107,227,160,.25); }

/* controls */
.btn, .chip {
  font: 500 13px/1 var(--mono); color: var(--text); background: var(--panel-2);
  border: 1px solid var(--rule-hi); border-radius: 6px; padding: 9px 14px; cursor: pointer;
  transition: border-color .15s, color .15s, background .15s;
}
.btn:hover, .chip:hover { border-color: var(--cyan-dim); color: #fff; }
.btn.primary { background: rgba(62,230,255,.1); border-color: var(--cyan-dim); color: var(--cyan); }
.chip[aria-pressed="true"] { background: rgba(62,230,255,.12); border-color: var(--cyan); color: var(--cyan); }
.chip.warn[aria-pressed="true"] { background: rgba(255,93,108,.12); border-color: var(--red); color: var(--red); }
.row { display: flex; flex-wrap: wrap; gap: 8px; align-items: center; }
input[type="range"] { -webkit-appearance: none; appearance: none; width: 100%; height: 4px; background: var(--rule-hi); border-radius: 2px; outline-offset: 6px; }
input[type="range"]::-webkit-slider-thumb { -webkit-appearance: none; width: 16px; height: 16px; border-radius: 50%; background: var(--cyan); box-shadow: 0 0 12px var(--cyan); cursor: pointer; }
input[type="range"]::-moz-range-thumb { width: 16px; height: 16px; border: 0; border-radius: 50%; background: var(--cyan); box-shadow: 0 0 12px var(--cyan); cursor: pointer; }

/* bars */
.bar { position: relative; height: 22px; background: var(--void); border: 1px solid var(--rule); border-radius: 4px; overflow: hidden; }
.bar > span { position: absolute; inset: 0 auto 0 0; background: linear-gradient(90deg, var(--cyan-dim), var(--cyan)); transition: width .5s cubic-bezier(.2,.8,.2,1); }
.bar.amber > span { background: linear-gradient(90deg, #a8701f, var(--amber)); }
.bar.green > span { background: linear-gradient(90deg, #2c8a5a, var(--green)); }
.bar.red > span { background: linear-gradient(90deg, #a0303a, var(--red)); }

/* ---------- chapter footer nav ---------- */
.pager { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; margin-top: 64px; }
.pager a { display: block; padding: 18px 20px; border: 1px solid var(--rule); border-radius: 10px; text-decoration: none; background: var(--panel); transition: border-color .15s; }
.pager a:hover { border-color: var(--cyan-dim); }
.pager small { display: block; font: 11px/1 var(--mono); letter-spacing: .14em; color: var(--text-faint); text-transform: uppercase; margin-bottom: 8px; }
.pager span { font: 600 18px/1.3 var(--sans); color: #fff; }
.pager .next { text-align: right; grid-column: 2; }

/* ---------- footer ---------- */
.foot { border-top: 1px solid var(--rule); padding: 40px 0 56px; font: 13px/1.6 var(--mono); color: var(--text-faint); }
.foot .wrap { display: flex; flex-wrap: wrap; gap: 12px 28px; justify-content: space-between; }
.foot a { color: var(--text-dim); text-decoration: none; }
.foot a:hover { color: var(--cyan); }

/* reveal on scroll (progressive: content visible without JS) */
.js .rise { opacity: 0; transform: translateY(18px); transition: opacity .7s ease, transform .7s cubic-bezier(.2,.8,.2,1); }
.js .rise.seen { opacity: 1; transform: none; }

@media (prefers-reduced-motion: reduce) {
  *, *::before, *::after { animation: none !important; transition: none !important; scroll-behavior: auto !important; }
  .js .rise { opacity: 1; transform: none; }
}
@media (max-width: 640px) { body { font-size: 17px; } .ch-hero .num { display: none; } .pager { grid-template-columns: 1fr; } .pager .next { grid-column: 1; } }

/* collapsed per-chapter references */
.refbox { margin-top: 64px; border-top: 1px solid var(--rule); padding-top: 14px; }
.refbox > summary { cursor: pointer; list-style: none; font: 500 12px/1 var(--mono); letter-spacing: .14em; text-transform: uppercase; color: var(--text-faint); padding: 6px 0; }
.refbox > summary::-webkit-details-marker { display: none; }
.refbox > summary::before { content: "+ "; color: var(--cyan-dim); }
.refbox[open] > summary::before { content: "− "; }
.refbox > summary:hover { color: var(--text-dim); }
.refbox .refs { margin-top: 16px; }

/* case-study callout (author's own projects) */
.note.case { border-left-color: var(--violet); background: radial-gradient(ellipse at 100% 0%, rgba(168,139,255,.07), transparent 60%), var(--panel); }
.note.case b { color: var(--violet); }
.note.case p { margin: 0 0 .9em; }
.note.case ol { margin: 0 0 .9em; padding-left: 1.2em; }
.note.case li { margin-bottom: .5em; }
.note.case p:last-child { margin-bottom: 0; }

/* citations must not stretch line height */
sup { line-height: 0; }

/* shared instrument hint: one colour, one phrasing ("▸ Try: …"); add .done when the suggested state is reached */
.instrument .hint { font: 500 12.5px/1.5 var(--mono); color: var(--amber); letter-spacing: .02em; }
.instrument .hint::before { content: "▸ Try: "; font-weight: 600; }
.instrument .hint.done { color: var(--green); }
.instrument .hint.done::before { content: "✓ "; }

/* chapter switcher in the HUD + on-this-page for narrow screens (built by site.js) */
.chmenu { position: relative; }
.chmenu > summary { list-style: none; cursor: pointer; color: var(--text-dim); }
.chmenu > summary::-webkit-details-marker { display: none; }
.chmenu > summary:hover, .chmenu[open] > summary { color: var(--cyan); }
.chmenu ol { position: absolute; right: 0; top: calc(100% + 14px); min-width: 280px; margin: 0; padding: 8px; list-style: none; background: var(--panel); border: 1px solid var(--rule-hi); border-radius: 10px; box-shadow: 0 20px 40px rgba(0,0,0,.5); z-index: 60; }
.chmenu li a { display: flex; gap: 12px; padding: 9px 10px; border-radius: 6px; color: var(--text); font: 500 13px/1.3 var(--mono); }
.chmenu li a span { color: var(--text-faint); min-width: 22px; }
.chmenu li a:hover, .chmenu li a[aria-current="page"] { background: rgba(62,230,255,.08); color: var(--cyan); }
.otp { display: none; margin: 24px 0 0; border: 1px solid var(--rule); border-radius: 10px; background: var(--panel); font: 13px/1.5 var(--mono); }
.otp > summary { padding: 12px 14px; cursor: pointer; color: var(--text-dim); letter-spacing: .12em; text-transform: uppercase; font-size: 11.5px; }
.otp ol { margin: 0; padding: 0 14px 12px 32px; }
.otp a { color: var(--text); text-decoration: none; display: block; padding: 5px 0; }
@media (max-width: 980px) { .otp { display: block; } }

/* touch: bigger targets on coarse pointers (WCAG 2.5.8) */
@media (pointer: coarse) {
  .chip, .btn { min-height: 40px; }
  input[type="range"] { height: 28px; background: transparent; }
  input[type="range"]::-webkit-slider-runnable-track { height: 4px; background: var(--rule-hi); border-radius: 2px; }
  input[type="range"]::-webkit-slider-thumb { width: 24px; height: 24px; margin-top: -10px; }
  input[type="range"]::-moz-range-thumb { width: 24px; height: 24px; }
}

/* never hide content from print, reader modes or captures */
@media print { .js .rise { opacity: 1 !important; transform: none !important; } .hud, .rail, .chmenu, .otp { display: none !important; } body { background: #fff; color: #111; } }

/* "Copy this" code blocks */
.code-cap { margin: 2em 0 .5em; font: 600 11.5px/1.4 var(--mono); letter-spacing: .14em; text-transform: uppercase; color: var(--cyan); }
.code-cap + pre { margin-top: 0; }
pre code { white-space: pre; }

/* instrument header: tag on its own line on phones */
@media (max-width: 640px) {
  .instrument > header { flex-wrap: wrap; row-gap: 6px; line-height: 1.4; }
  .instrument > header .tag { margin-left: 15px; flex-basis: 100%; }
}

/* anchor jumps land below the sticky header */
html { scroll-padding-top: 76px; }
/* chapter switcher on phones: full-width sheet instead of overflowing the left edge */
@media (max-width: 640px) {
  .chmenu ol { position: fixed; left: 16px; right: 16px; top: 58px; min-width: 0; }
}
/* touch targets: checkboxes and inline citation links */
@media (pointer: coarse) {
  input[type="checkbox"] { min-width: 24px; min-height: 24px; }
  sup.cite a { display: inline-block; min-width: 24px; min-height: 24px; line-height: 24px; text-align: center; }
}

/* long inline tokens (flags, attribute names, URLs) must wrap on phones */
.prose { overflow-wrap: break-word; }
:not(pre) > code { overflow-wrap: anywhere; }