/* ==========================================================================
   KSA Beauty Tech Playbook — site stylesheet
   Light is the default token set; dark is selected (not auto-inverted).
   ========================================================================== */

:root {
  color-scheme: light;
  --bg: #f4f3ef;
  --surface: #fcfcfb;
  --surface-2: #f0efea;
  --ink: #0b0b0b;
  --ink-2: #52514e;
  --muted: #6f6d68;
  --axis-text: #898781;
  --grid: #e1e0d9;
  --axis: #c3c2b7;
  --border: rgba(11, 11, 11, 0.10);
  --border-strong: rgba(11, 11, 11, 0.18);

  --accent: #2a78d6;
  --accent-ink: #1c5cab;
  --accent-wash: #e8f1fc;
  --accent-contrast: #ffffff;

  /* validated categorical palette (light) */
  --s1: #2a78d6;
  --s2: #eb6834;
  --s3: #1baf7a;
  --s4: #eda100;
  --s5: #e87ba4;
  --s-neutral: #b9b7ae;

  /* status — always paired with an icon + label */
  --good: #0ca30c;
  --good-text: #006300;
  --warning: #fab219;
  --serious: #ec835a;
  --critical: #d03b3b;
  --critical-text: #b42525;
  --critical-wash: rgba(208, 59, 59, 0.10);
  --good-wash: rgba(12, 163, 12, 0.10);

  --radius: 14px;
  --radius-sm: 8px;
  --shadow: 0 1px 2px rgba(11, 11, 11, 0.04), 0 8px 24px rgba(11, 11, 11, 0.05);
  --font: system-ui, -apple-system, "Segoe UI", Roboto, "Helvetica Neue", Arial, sans-serif;
  --mono: ui-monospace, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;
  --maxw: 1160px;
  --gutter: clamp(16px, 4vw, 40px);
  --header-h: 64px;
}

@media (prefers-color-scheme: dark) {
  :root:where(:not([data-theme="light"])) {
    color-scheme: dark;
    --bg: #0d0d0d;
    --surface: #1a1a19;
    --surface-2: #222220;
    --ink: #ffffff;
    --ink-2: #c3c2b7;
    --muted: #a09e96;
    --axis-text: #898781;
    --grid: #2c2c2a;
    --axis: #383835;
    --border: rgba(255, 255, 255, 0.10);
    --border-strong: rgba(255, 255, 255, 0.18);
    --accent: #3987e5;
    --accent-ink: #86b6ef;
    --accent-wash: rgba(57, 135, 229, 0.14);
    --accent-contrast: #ffffff;
    --s1: #3987e5;
    --s2: #d95926;
    --s3: #199e70;
    --s4: #c98500;
    --s5: #d55181;
    --s-neutral: #5c5b56;
    --good-text: #0ca30c;
    --critical-text: #e66767;
    --critical-wash: rgba(230, 103, 103, 0.14);
    --good-wash: rgba(12, 163, 12, 0.16);
    --shadow: 0 1px 2px rgba(0, 0, 0, 0.4), 0 8px 24px rgba(0, 0, 0, 0.35);
  }
}

:root[data-theme="dark"] {
  color-scheme: dark;
  --bg: #0d0d0d;
  --surface: #1a1a19;
  --surface-2: #222220;
  --ink: #ffffff;
  --ink-2: #c3c2b7;
  --muted: #a09e96;
  --axis-text: #898781;
  --grid: #2c2c2a;
  --axis: #383835;
  --border: rgba(255, 255, 255, 0.10);
  --border-strong: rgba(255, 255, 255, 0.18);
  --accent: #3987e5;
  --accent-ink: #86b6ef;
  --accent-wash: rgba(57, 135, 229, 0.14);
  --accent-contrast: #ffffff;
  --s1: #3987e5;
  --s2: #d95926;
  --s3: #199e70;
  --s4: #c98500;
  --s5: #d55181;
  --s-neutral: #5c5b56;
  --good-text: #0ca30c;
  --critical-text: #e66767;
  --critical-wash: rgba(230, 103, 103, 0.14);
  --good-wash: rgba(12, 163, 12, 0.16);
  --shadow: 0 1px 2px rgba(0, 0, 0, 0.4), 0 8px 24px rgba(0, 0, 0, 0.35);
}

/* ---------- base ---------- */
*, *::before, *::after { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: calc(var(--header-h) + 16px); }
@media (prefers-reduced-motion: reduce) { html { scroll-behavior: auto; } }
body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--font);
  font-size: 16px;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}
img, svg { max-width: 100%; }
a { color: var(--accent-ink); text-underline-offset: 3px; text-decoration-thickness: 1px; }
a:hover { text-decoration-thickness: 2px; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; border-radius: 4px; }
h1, h2, h3, h4 { line-height: 1.2; margin: 0 0 .5em; letter-spacing: -0.015em; }
h1 { font-size: clamp(2rem, 4.6vw, 3.4rem); font-weight: 750; letter-spacing: -0.03em; }
h2 { font-size: clamp(1.45rem, 2.6vw, 2rem); font-weight: 700; }
h3 { font-size: 1.15rem; font-weight: 650; }
h4 { font-size: 1rem; font-weight: 650; }
p { margin: 0 0 1em; }
strong { font-weight: 650; }
code { font-family: var(--mono); font-size: .9em; background: var(--surface-2); padding: .1em .35em; border-radius: 5px; }
hr { border: 0; border-top: 1px solid var(--border); margin: 3rem 0; }
.skip-link { position: absolute; left: -999px; top: 8px; background: var(--ink); color: var(--bg); padding: 8px 12px; border-radius: 8px; z-index: 100; }
.skip-link:focus { left: 8px; }

.container { max-width: var(--maxw); margin: 0 auto; padding-inline: var(--gutter); }
.prose { max-width: 72ch; }
.prose p, .prose li { color: var(--ink-2); }
.prose p strong, .prose li strong { color: var(--ink); }
.lede { font-size: clamp(1.05rem, 1.6vw, 1.25rem); color: var(--ink-2); max-width: 62ch; }
.muted { color: var(--muted); }
.small { font-size: .875rem; }
.kicker {
  display: inline-flex; align-items: center; gap: .5rem;
  font-size: .75rem; font-weight: 650; letter-spacing: .12em; text-transform: uppercase;
  color: var(--accent-ink);
}
.kicker::before { content: ""; width: 18px; height: 2px; background: var(--accent); border-radius: 2px; }

/* ---------- progress + header ---------- */
.progress { position: fixed; top: 0; left: 0; height: 3px; width: 0; background: var(--accent); z-index: 60; transition: width .1s linear; }
.site-header {
  position: sticky; top: 0; z-index: 50;
  background: color-mix(in srgb, var(--bg) 82%, transparent);
  backdrop-filter: saturate(1.4) blur(14px);
  -webkit-backdrop-filter: saturate(1.4) blur(14px);
  border-bottom: 1px solid var(--border);
}
.header-inner { display: flex; align-items: center; gap: 1rem; height: var(--header-h); }
.brand { display: flex; align-items: center; gap: .6rem; color: var(--ink); text-decoration: none; font-weight: 700; letter-spacing: -0.01em; flex-shrink: 0; }
.brand-mark {
  width: 36px; height: 30px; border-radius: 9px; display: grid; place-items: center;
  background: var(--accent); color: #fff; font-size: .72rem; font-weight: 800; letter-spacing: 0;
}
.brand small { display: block; font-weight: 500; font-size: .72rem; color: var(--muted); letter-spacing: 0; line-height: 1.1; }
.brand span { line-height: 1.15; font-size: .95rem; }
.nav { margin-left: auto; display: flex; align-items: center; gap: .15rem; }
.nav a {
  color: var(--ink-2); text-decoration: none; font-size: .88rem; font-weight: 550;
  padding: .45rem .65rem; border-radius: 999px; white-space: nowrap;
}
.nav a:hover { background: var(--surface-2); color: var(--ink); }
.nav a[aria-current="page"] { background: var(--ink); color: var(--bg); }
.icon-btn {
  width: 38px; height: 38px; border-radius: 999px; display: inline-grid; place-items: center;
  border: 1px solid var(--border); background: var(--surface); color: var(--ink); cursor: pointer; flex-shrink: 0;
}
.icon-btn:hover { border-color: var(--border-strong); }
.icon-btn svg { width: 18px; height: 18px; }
.menu-btn { display: none; }
@media (max-width: 1120px) {
  .menu-btn { display: inline-grid; margin-left: auto; }
  .nav {
    position: fixed; inset: var(--header-h) 0 auto 0; flex-direction: column; align-items: stretch;
    background: var(--surface); border-bottom: 1px solid var(--border); padding: .75rem var(--gutter) 1.25rem;
    gap: .25rem; box-shadow: var(--shadow); transform: translateY(-8px); opacity: 0; pointer-events: none;
    transition: opacity .18s ease, transform .18s ease; max-height: calc(100vh - var(--header-h)); overflow-y: auto;
  }
  .nav.open { opacity: 1; transform: none; pointer-events: auto; }
  .nav a { padding: .7rem .9rem; font-size: 1rem; border-radius: 10px; }
  .nav a .num { display: inline-block; width: 2.2em; color: var(--muted); }
  .nav a[aria-current="page"] .num { color: inherit; opacity: .7; }
}
@media (min-width: 1121px) { .nav a .num { display: none; } }

/* ---------- hero ---------- */
.page-hero { padding-block: clamp(2.5rem, 6vw, 5rem) clamp(1.5rem, 3vw, 2.5rem); }
.page-hero h1 { margin-top: .6rem; max-width: 20ch; }
.page-hero.home h1 { max-width: 22ch; }
.hero-meta { display: flex; flex-wrap: wrap; gap: .5rem; margin-top: 1.5rem; }
.chip {
  display: inline-flex; align-items: center; gap: .4rem; font-size: .8rem; font-weight: 550;
  padding: .35rem .75rem; border-radius: 999px; background: var(--surface); border: 1px solid var(--border); color: var(--ink-2);
}
.chip .dot { width: 7px; height: 7px; border-radius: 50%; background: var(--accent); }

/* ---------- sections ---------- */
main { padding-bottom: 4rem; }
.section { padding: clamp(2rem, 4vw, 3.25rem) 0; border-top: 1px solid var(--border); }
.section:first-of-type { border-top: 0; }
.section-head { display: flex; flex-wrap: wrap; align-items: baseline; gap: .25rem 1rem; margin-bottom: 1.25rem; }
.section-head .sec-num { font-family: var(--mono); font-size: .85rem; color: var(--muted); }
.section-head h2 { margin: 0; }
.section-intro { margin-bottom: 1.75rem; }

.grid { display: grid; gap: 1rem; }
.grid-2 { grid-template-columns: repeat(2, minmax(0, 1fr)); }
.grid-3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.grid-4 { grid-template-columns: repeat(4, minmax(0, 1fr)); }
.grid-5 { grid-template-columns: repeat(5, minmax(0, 1fr)); }
@media (max-width: 1000px) { .grid-4, .grid-5 { grid-template-columns: repeat(2, minmax(0, 1fr)); } .grid-3 { grid-template-columns: repeat(2, minmax(0, 1fr)); } }
@media (max-width: 680px) { .grid-2, .grid-3, .grid-4, .grid-5 { grid-template-columns: minmax(0, 1fr); } }
.split { display: grid; grid-template-columns: minmax(0, 1.05fr) minmax(0, 1fr); gap: clamp(1.5rem, 3vw, 2.5rem); align-items: start; }
@media (max-width: 900px) { .split { grid-template-columns: minmax(0, 1fr); } }

.card {
  background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius);
  padding: clamp(1.1rem, 2vw, 1.5rem); box-shadow: var(--shadow); min-width: 0;
}
.card h3 { margin-bottom: .4rem; }
.card p { color: var(--ink-2); margin-bottom: .6rem; }
.card p:last-child { margin-bottom: 0; }
.card .card-num {
  display: inline-grid; place-items: center; width: 32px; height: 32px; border-radius: 10px;
  background: var(--accent-wash); color: var(--accent-ink); font-weight: 750; font-size: .9rem; margin-bottom: .85rem;
}
.card .tag { font-size: .75rem; font-weight: 650; letter-spacing: .06em; text-transform: uppercase; color: var(--muted); display: block; margin-bottom: .4rem; }
a.card { text-decoration: none; color: inherit; transition: transform .18s ease, border-color .18s ease; display: block; }
a.card:hover { transform: translateY(-2px); border-color: var(--border-strong); }
a.card .arrow { color: var(--accent-ink); font-weight: 650; font-size: .9rem; margin-top: .75rem; display: inline-block; }

/* stat tiles */
.stat { display: flex; flex-direction: column; gap: .3rem; }
.stat .label { font-size: .85rem; color: var(--ink-2); font-weight: 550; }
.stat .value { font-size: clamp(1.8rem, 3.2vw, 2.4rem); font-weight: 700; letter-spacing: -0.03em; line-height: 1.05; }
.stat .value.sm { font-size: clamp(1.35rem, 2.2vw, 1.7rem); }
.stat .sub { font-size: .82rem; color: var(--muted); }
.stat .sub a { color: var(--muted); }
.delta-good { color: var(--good-text); font-weight: 650; }
.delta-bad { color: var(--critical-text); font-weight: 650; }

/* hero figure */
.hero-figure { font-size: clamp(3rem, 7vw, 4.5rem); font-weight: 750; letter-spacing: -0.04em; line-height: 1; }

/* meter (progress toward target) */
.meter { margin-top: .75rem; }
.meter-track { position: relative; height: 12px; border-radius: 999px; background: var(--accent-wash); overflow: visible; }
.meter-fill { position: absolute; left: 0; top: 0; bottom: 0; border-radius: 999px; background: var(--accent); }
.meter-mark { position: absolute; top: -5px; bottom: -5px; width: 2px; background: var(--ink); border-radius: 2px; }
.meter-mark.baseline { background: var(--axis-text); }
.meter-legend { display: flex; justify-content: space-between; flex-wrap: wrap; gap: .5rem; margin-top: .65rem; font-size: .82rem; color: var(--ink-2); }
.meter-legend b { color: var(--ink); }

/* callouts */
.callout {
  display: grid; grid-template-columns: auto 1fr; gap: .85rem; align-items: start;
  border-radius: var(--radius); padding: 1rem 1.15rem; border: 1px solid var(--border); background: var(--surface);
}
.callout .ic { width: 28px; height: 28px; border-radius: 8px; display: grid; place-items: center; font-weight: 800; font-size: .9rem; }
.callout p { margin: 0 0 .4rem; color: var(--ink-2); }
.callout p:last-child { margin: 0; }
.callout strong.title { display: block; color: var(--ink); margin-bottom: .2rem; }
.callout.info .ic { background: var(--accent-wash); color: var(--accent-ink); }
.callout.warn { border-color: color-mix(in srgb, var(--warning) 55%, transparent); background: color-mix(in srgb, var(--warning) 9%, var(--surface)); }
.callout.warn .ic { background: var(--warning); color: #3a2a00; }
.callout.fix { border-color: color-mix(in srgb, var(--serious) 55%, transparent); background: color-mix(in srgb, var(--serious) 8%, var(--surface)); }
.callout.fix .ic { background: var(--serious); color: #3b1405; }
.callout.good .ic { background: var(--good); color: #fff; }

/* tables */
.table-wrap { overflow-x: auto; border: 1px solid var(--border); border-radius: var(--radius); background: var(--surface); box-shadow: var(--shadow); }
table { border-collapse: collapse; width: 100%; font-size: .92rem; }
th, td { padding: .75rem 1rem; text-align: left; vertical-align: top; border-bottom: 1px solid var(--border); }
thead th { font-size: .78rem; text-transform: uppercase; letter-spacing: .06em; color: var(--muted); font-weight: 650; background: var(--surface-2); white-space: nowrap; }
tbody tr:last-child td { border-bottom: 0; }
tbody tr:hover td { background: color-mix(in srgb, var(--surface-2) 60%, transparent); }
td.num, th.num { text-align: right; font-variant-numeric: tabular-nums; white-space: nowrap; }
tr.total td { font-weight: 700; background: var(--surface-2); color: var(--ink); }
tr.subtotal td { font-weight: 650; color: var(--ink); }
td .note { display: block; font-size: .8rem; color: var(--muted); margin-top: .15rem; }
td.neg { color: var(--critical-text); }
td.pos { color: var(--good-text); }
.table-caption { font-size: .82rem; color: var(--muted); margin-top: .65rem; max-width: 90ch; }
.col-highlight { background: color-mix(in srgb, var(--accent-wash) 70%, transparent); }
table.compact th, table.compact td { padding: .5rem .75rem; }

/* ---------- chart cards ---------- */
.chart-card { background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); box-shadow: var(--shadow); padding: clamp(1rem, 2vw, 1.4rem); min-width: 0; }
.chart-head { display: flex; justify-content: space-between; align-items: flex-start; gap: 1rem; margin-bottom: .75rem; }
.chart-head h3 { margin: 0 0 .2rem; font-size: 1.05rem; }
.chart-head p { margin: 0; font-size: .85rem; color: var(--ink-2); }
.chart-tools { display: flex; gap: .4rem; flex-shrink: 0; }
.btn-ghost {
  font: inherit; font-size: .78rem; font-weight: 600; color: var(--ink-2); background: transparent;
  border: 1px solid var(--border); border-radius: 999px; padding: .3rem .7rem; cursor: pointer; white-space: nowrap;
}
.btn-ghost:hover { color: var(--ink); border-color: var(--border-strong); }
.btn-ghost[aria-pressed="true"] { background: var(--ink); color: var(--bg); border-color: var(--ink); }
.chart { position: relative; width: 100%; }
.chart svg { display: block; overflow: visible; }
.chart-foot { font-size: .78rem; color: var(--muted); margin-top: .6rem; }
.chart-table { margin-top: .9rem; }
.chart-table[hidden] { display: none; }
.legend { display: flex; flex-wrap: wrap; gap: .4rem 1.1rem; margin: 0 0 .6rem; padding: 0; list-style: none; font-size: .82rem; color: var(--ink-2); }
.legend li { display: inline-flex; align-items: center; gap: .45rem; }
.legend .sw { width: 12px; height: 12px; border-radius: 3px; }
.legend .ln { width: 16px; height: 2px; border-radius: 2px; }

/* svg chrome */
.ax-text { fill: var(--axis-text); font-size: 11.5px; font-family: var(--font); font-variant-numeric: tabular-nums; }
.ax-label { fill: var(--ink-2); font-size: 12px; font-family: var(--font); }
.val-label { fill: var(--ink); font-size: 12px; font-weight: 650; font-family: var(--font); }
.val-label.muted { fill: var(--ink-2); font-weight: 550; }
.grid-line { stroke: var(--grid); stroke-width: 1; shape-rendering: crispEdges; }
.base-line { stroke: var(--axis); stroke-width: 1; shape-rendering: crispEdges; }
.zero-line { stroke: var(--ink-2); stroke-width: 1; shape-rendering: crispEdges; opacity: .6; }
.mark { transition: opacity .12s ease; }
.mark-hit { fill: transparent; cursor: pointer; }
.mark-hit:focus { outline: none; }
.chart.focus-mode .mark.dimmable { opacity: .45; }
.chart .mark.dimmable.active { opacity: 1; }
.crosshair { stroke: var(--ink-2); stroke-width: 1; opacity: .5; shape-rendering: crispEdges; }
.annot-text { fill: var(--ink); font-size: 12px; font-weight: 600; font-family: var(--font); }
.annot-line { stroke: var(--ink-2); stroke-width: 1; }

.tooltip {
  position: absolute; pointer-events: none; z-index: 10; min-width: 140px; max-width: 260px;
  background: var(--surface); color: var(--ink); border: 1px solid var(--border-strong); border-radius: 10px;
  padding: .55rem .7rem; font-size: .82rem; box-shadow: 0 10px 30px rgba(0,0,0,.14); opacity: 0; transform: translateY(4px);
  transition: opacity .1s ease, transform .1s ease;
}
.tooltip.show { opacity: 1; transform: none; }
.tooltip .tt-title { font-size: .75rem; color: var(--ink-2); margin-bottom: .3rem; font-weight: 600; }
.tooltip .tt-row { display: flex; align-items: center; gap: .5rem; justify-content: space-between; }
.tooltip .tt-row + .tt-row { margin-top: .2rem; }
.tooltip .tt-key { display: inline-flex; align-items: center; gap: .4rem; color: var(--ink-2); }
.tooltip .tt-key i { width: 12px; height: 2px; border-radius: 2px; display: inline-block; }
.tooltip .tt-val { font-weight: 700; font-variant-numeric: tabular-nums; }

/* ---------- ascii / code ---------- */
.ascii {
  font-family: var(--mono); font-size: clamp(.62rem, 1.4vw, .82rem); line-height: 1.45; white-space: pre; overflow-x: auto;
  background: var(--surface-2); border: 1px solid var(--border); border-radius: var(--radius); padding: 1.1rem 1.25rem; color: var(--ink);
}
details.code { border: 1px solid var(--border); border-radius: var(--radius); background: var(--surface); margin-top: 1rem; overflow: hidden; }
details.code summary {
  cursor: pointer; list-style: none; padding: .8rem 1rem; font-weight: 600; font-size: .9rem; display: flex; align-items: center; gap: .6rem;
}
details.code summary::-webkit-details-marker { display: none; }
details.code summary::before { content: "›"; font-size: 1.2rem; line-height: 1; color: var(--muted); transition: transform .15s ease; }
details.code[open] summary::before { transform: rotate(90deg); }
details.code summary .lang { margin-left: auto; font-family: var(--mono); font-size: .75rem; color: var(--muted); font-weight: 500; }
.code-body { position: relative; border-top: 1px solid var(--border); }
.code-body pre { margin: 0; padding: 1rem 1.1rem; overflow-x: auto; font-family: var(--mono); font-size: .8rem; line-height: 1.55; background: var(--surface-2); color: var(--ink); }
.copy-btn { position: absolute; top: .6rem; right: .6rem; }

/* ---------- forms / calculators ---------- */
.controls { display: grid; grid-template-columns: repeat(auto-fill, minmax(215px, 1fr)); gap: .85rem 1rem; }
.field { display: flex; flex-direction: column; gap: .3rem; min-width: 0; }
.field label { font-size: .8rem; font-weight: 600; color: var(--ink-2); display: flex; justify-content: space-between; gap: .5rem; }
.field label output { color: var(--ink); font-variant-numeric: tabular-nums; }
.field input[type="number"] {
  font: inherit; font-size: .95rem; padding: .5rem .65rem; border-radius: 10px; border: 1px solid var(--border-strong);
  background: var(--surface); color: var(--ink); width: 100%; font-variant-numeric: tabular-nums;
}
.field input[type="range"] { width: 100%; accent-color: var(--accent); }
.field .hint { font-size: .74rem; color: var(--muted); }
.toggle-row { display: flex; flex-wrap: wrap; gap: .5rem; align-items: center; margin: 0 0 1rem; }
.seg { display: inline-flex; border: 1px solid var(--border-strong); border-radius: 999px; padding: 3px; background: var(--surface); }
.seg button { font: inherit; font-size: .82rem; font-weight: 600; border: 0; background: transparent; color: var(--ink-2); padding: .35rem .8rem; border-radius: 999px; cursor: pointer; }
.seg button[aria-pressed="true"] { background: var(--ink); color: var(--bg); }
.switch { display: inline-flex; align-items: center; gap: .55rem; font-size: .88rem; font-weight: 600; color: var(--ink-2); cursor: pointer; user-select: none; }
.switch input { width: 38px; height: 22px; appearance: none; -webkit-appearance: none; background: var(--axis); border-radius: 999px; position: relative; cursor: pointer; transition: background .15s ease; margin: 0; }
.switch input::after { content: ""; position: absolute; top: 3px; left: 3px; width: 16px; height: 16px; border-radius: 50%; background: #fff; transition: transform .15s ease; }
.switch input:checked { background: var(--accent); }
.switch input:checked::after { transform: translateX(16px); }
.btn {
  font: inherit; font-size: .88rem; font-weight: 650; padding: .55rem 1rem; border-radius: 999px; cursor: pointer;
  border: 1px solid var(--ink); background: var(--ink); color: var(--bg);
}
.btn.secondary { background: transparent; color: var(--ink); border-color: var(--border-strong); }

/* ---------- formula ---------- */
.formula { display: flex; align-items: center; gap: 1rem; flex-wrap: wrap; font-size: clamp(.95rem, 1.8vw, 1.1rem); }
.formula .lhs { font-weight: 750; white-space: nowrap; }
.frac { display: inline-flex; flex-direction: column; align-items: center; text-align: center; }
.frac .top { padding: 0 .5rem .4rem; border-bottom: 2px solid var(--ink); }
.frac .bot { padding: .4rem .5rem 0; }

/* ---------- quadrant ---------- */
.quad-wrap { position: relative; padding: 2rem 0 2.4rem; }
.quad { display: grid; grid-template-columns: 1fr 1fr; grid-template-rows: 1fr 1fr; gap: 10px; }
.quad-cell {
  border-radius: var(--radius); padding: 1.1rem 1.2rem; border: 1px solid var(--border); background: var(--surface);
  min-height: 190px; transition: transform .15s ease, border-color .15s ease; cursor: default;
}
.quad-cell:hover, .quad-cell:focus-within { border-color: var(--border-strong); transform: translateY(-1px); }
.quad-cell h4 { margin: .2rem 0 .5rem; }
.quad-cell ul { margin: 0; padding-left: 1.1rem; color: var(--ink-2); font-size: .9rem; }
.quad-cell .q-label { font-size: .72rem; letter-spacing: .08em; text-transform: uppercase; color: var(--muted); font-weight: 650; }
.quad-cell.target { background: var(--accent); border-color: var(--accent); color: #fff; }
.quad-cell.target .q-label, .quad-cell.target ul { color: rgba(255,255,255,.88); }
.quad-cell.target h4 { color: #fff; }
.quad-axis-y { position: absolute; left: 0; top: 2rem; bottom: 2rem; width: 1.6rem; display: flex; align-items: center; justify-content: center; }
.quad-axis-y span { transform: rotate(-90deg); white-space: nowrap; font-size: .75rem; font-weight: 650; letter-spacing: .06em; text-transform: uppercase; color: var(--muted); }
.quad-axis-x { display: flex; justify-content: space-between; font-size: .75rem; font-weight: 650; letter-spacing: .06em; text-transform: uppercase; color: var(--muted); margin-top: .6rem; }
.quad-axis-top { text-align: center; font-size: .75rem; font-weight: 650; letter-spacing: .06em; text-transform: uppercase; color: var(--muted); position: absolute; top: .4rem; left: 0; right: 0; }
.quad-axis-bottom { text-align: center; font-size: .75rem; font-weight: 650; letter-spacing: .06em; text-transform: uppercase; color: var(--muted); position: absolute; bottom: .2rem; left: 0; right: 0; }
@media (max-width: 600px) { .quad { grid-template-columns: 1fr; grid-template-rows: none; } .quad-wrap { padding-left: 0; } .quad-axis-y { display: none; } .quad-axis-top, .quad-axis-bottom { left: 0; } }

/* ---------- roadmap ---------- */
.roadmap { position: relative; display: grid; gap: 1.25rem; }
.stage { display: grid; grid-template-columns: 64px minmax(0, 1fr); gap: 1.1rem; position: relative; }
.stage-rail { display: flex; flex-direction: column; align-items: center; }
.stage-dot {
  width: 52px; height: 52px; border-radius: 16px; display: grid; place-items: center; font-weight: 800; font-size: 1.15rem;
  background: var(--accent-wash); color: var(--accent-ink); border: 1px solid var(--border);
}
.stage.done .stage-dot { background: var(--accent); color: #fff; }
.stage-line { flex: 1; width: 2px; background: var(--grid); margin-top: .5rem; border-radius: 2px; min-height: 30px; }
.stage:last-child .stage-line { display: none; }
@media (max-width: 600px) { .stage { grid-template-columns: 40px minmax(0, 1fr); gap: .7rem; } .stage-dot { width: 40px; height: 40px; border-radius: 12px; font-size: 1rem; } }
.stage .card { margin-bottom: .25rem; }
.stage-top { display: flex; flex-wrap: wrap; justify-content: space-between; align-items: baseline; gap: .5rem; }
.stage-top h3 { margin: 0; }
.pill { font-size: .75rem; font-weight: 650; padding: .25rem .6rem; border-radius: 999px; background: var(--surface-2); color: var(--ink-2); border: 1px solid var(--border); white-space: nowrap; }
.checklist { list-style: none; margin: 1rem 0 0; padding: 0; display: grid; gap: .35rem; }
.checklist label { display: flex; gap: .65rem; align-items: flex-start; padding: .45rem .55rem; border-radius: 10px; cursor: pointer; color: var(--ink-2); font-size: .93rem; }
.checklist label:hover { background: var(--surface-2); }
.checklist input { margin-top: .25rem; accent-color: var(--accent); width: 16px; height: 16px; flex-shrink: 0; }
.checklist input:checked + span { color: var(--muted); text-decoration: line-through; text-decoration-color: var(--axis); }
.stage-progress { font-size: .8rem; color: var(--muted); margin-top: .6rem; }
.gate { margin-top: .9rem; font-size: .88rem; color: var(--ink-2); padding: .6rem .8rem; border-radius: 10px; background: var(--surface-2); }
.gate b { color: var(--ink); }

/* flow diagram */
.flow { display: flex; align-items: stretch; gap: .5rem; flex-wrap: wrap; }
.flow-node { flex: 1 1 140px; background: var(--surface); border: 1px solid var(--border); border-radius: 12px; padding: .85rem .9rem; text-align: center; min-width: 0; }
.flow-node b { display: block; font-size: .95rem; }
.flow-node span { font-size: .78rem; color: var(--muted); }
.flow-node.accent { border-color: var(--accent); box-shadow: inset 0 0 0 1px var(--accent); }
.flow-arrow { display: grid; place-items: center; color: var(--muted); font-size: 1.2rem; flex: 0 0 auto; }
@media (max-width: 700px) { .flow { flex-direction: column; } .flow-arrow { transform: rotate(90deg); } }

/* advantage stack */
.stack { display: grid; gap: .75rem; }
.stack-item { display: grid; grid-template-columns: 44px minmax(0, 1fr) auto; gap: 1rem; align-items: center; background: var(--surface); border: 1px solid var(--border); border-radius: var(--radius); padding: 1rem 1.15rem; box-shadow: var(--shadow); }
.stack-item .n { width: 44px; height: 44px; border-radius: 12px; display: grid; place-items: center; background: var(--accent-wash); color: var(--accent-ink); font-weight: 800; }
.stack-item h3 { margin: 0 0 .15rem; font-size: 1rem; }
.stack-item p { margin: 0; color: var(--ink-2); font-size: .9rem; }
.stack-item .what { font-size: .8rem; color: var(--muted); text-align: right; max-width: 22ch; }
@media (max-width: 700px) { .stack-item { grid-template-columns: 44px minmax(0, 1fr); } .stack-item .what { grid-column: 2; text-align: left; max-width: none; } }

/* sources */
.source-list { list-style: none; margin: 0; padding: 0; display: grid; gap: .6rem; }
.source-list li { background: var(--surface); border: 1px solid var(--border); border-radius: 12px; padding: .85rem 1rem; }
.source-list li b { display: block; color: var(--ink); font-size: .95rem; margin-bottom: .15rem; }
.source-list li span { color: var(--ink-2); font-size: .88rem; }
.source-list .where { font-size: .76rem; color: var(--muted); margin-top: .3rem; display: block; }
.badge { display: inline-block; font-size: .7rem; font-weight: 700; letter-spacing: .04em; text-transform: uppercase; padding: .15rem .45rem; border-radius: 6px; vertical-align: middle; margin-left: .35rem; }
.badge.src { background: var(--good-wash); color: var(--good-text); }
.badge.model { background: var(--accent-wash); color: var(--accent-ink); }
.badge.new { background: color-mix(in srgb, var(--serious) 18%, transparent); color: var(--ink); }
dl.glossary { display: grid; grid-template-columns: minmax(120px, 190px) minmax(0, 1fr); gap: .1rem 1.25rem; margin: 0; }
dl.glossary dt { font-weight: 700; padding: .6rem 0; border-top: 1px solid var(--border); }
dl.glossary dd { margin: 0; padding: .6rem 0; border-top: 1px solid var(--border); color: var(--ink-2); }
@media (max-width: 600px) { dl.glossary { grid-template-columns: 1fr; } dl.glossary dd { border-top: 0; padding-top: 0; } }

/* page nav + footer */
.pager { display: grid; grid-template-columns: 1fr 1fr; gap: 1rem; margin-top: 3rem; }
.pager a { display: block; padding: 1rem 1.2rem; border: 1px solid var(--border); border-radius: var(--radius); text-decoration: none; background: var(--surface); color: var(--ink); }
.pager a:hover { border-color: var(--border-strong); }
.pager small { display: block; color: var(--muted); font-size: .78rem; margin-bottom: .15rem; }
.pager .next { text-align: right; grid-column: 2; }
@media (max-width: 600px) { .pager { grid-template-columns: 1fr; } .pager .next { grid-column: 1; } }
.site-footer { border-top: 1px solid var(--border); padding: 2rem 0 3rem; color: var(--muted); font-size: .84rem; }
.site-footer .container { display: flex; flex-wrap: wrap; justify-content: space-between; gap: 1rem; }

/* toc on page */
.toc { display: flex; flex-wrap: wrap; gap: .4rem; margin-top: 1.25rem; }
.toc a { font-size: .82rem; text-decoration: none; color: var(--ink-2); border: 1px solid var(--border); background: var(--surface); padding: .3rem .7rem; border-radius: 999px; }
.toc a:hover { color: var(--ink); border-color: var(--border-strong); }

/* reveal */
.reveal { opacity: 0; transform: translateY(10px); transition: opacity .5s ease, transform .5s ease; }
.reveal.in { opacity: 1; transform: none; }
@media (prefers-reduced-motion: reduce) { .reveal { opacity: 1; transform: none; transition: none; } }

/* utilities */
.mt-0 { margin-top: 0; } .mt-1 { margin-top: 1rem; } .mt-2 { margin-top: 2rem; } .mb-0 { margin-bottom: 0; }
.stack-gap > * + * { margin-top: 1rem; }
.center { text-align: center; }
.nowrap { white-space: nowrap; }
.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; }

@media print {
  .site-header, .progress, .pager, .chart-tools, .copy-btn, .toggle-row { display: none !important; }
  body { background: #fff; }
  .card, .chart-card, .table-wrap { box-shadow: none; }
  .reveal { opacity: 1; transform: none; }
}