/* 01-tokens.css */
/* Design tokens — from v2/tokens.json. Radius is 0. There are no shadows. */

:root {
  --ink: #191817;
  --ink-deep: #14130f;
  --ink-well: #131211;
  --panel: #201f1d;
  --panel-alt: #1c1b19;
  --panel-soft: #1d1c1a;
  --paper: #e9e7e2;

  --text: #e9e7e2;
  --text-muted: #b3aea5;
  --text-dim: #8f8b83;
  --text-faint: #5f5c56;
  --formula: #86827b;

  --ink-on-paper: #191817;
  --ink-on-paper-muted: #4a463f;
  --ink-on-paper-dim: #6b665e;

  --amber: #e0b675;
  --cyan: #6fc0d8;

  --hairline: rgba(233, 231, 226, 0.14);
  --hairline-soft: rgba(233, 231, 226, 0.1);
  --hairline-strong: rgba(233, 231, 226, 0.24);
  --hairline-paper: rgba(25, 24, 23, 0.16);

  --font-display: "Anta", system-ui, "Segoe UI", sans-serif;
  --font-text: "Didact Gothic", system-ui, "Segoe UI", sans-serif;
  --font-mono: "JetBrains Mono", ui-monospace, "SFMono-Regular", Menlo, monospace;

  --container: 1240px;
  --pad-inline: clamp(20px, 5vw, 56px);
  --section-y: clamp(56px, 11vh, 130px);
  --gutter: 74px;

  --reveal-ease: cubic-bezier(0.2, 0.7, 0.2, 1);
}

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

/* 02-base.css */
/* Reset, elements, typography, layout primitives. */

html {
  -webkit-text-size-adjust: 100%;
}

body {
  margin: 0;
  background: var(--ink);
  color: var(--text-muted);
  font: 400 16.5px/1.75 var(--font-text);
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  overflow-x: hidden;
}

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

a {
  color: var(--text);
  text-decoration: none;
  transition: color 0.18s ease, border-color 0.18s ease, background 0.18s ease;
}
a:hover {
  color: var(--amber);
}

::selection {
  background: var(--amber);
  color: var(--ink);
}

:focus-visible {
  outline: 2px solid var(--cyan);
  outline-offset: 3px;
}

p {
  margin: 0 0 1em;
  text-wrap: pretty;
}
p:last-child {
  margin-bottom: 0;
}

h1,
h2,
h3 {
  font-family: var(--font-display);
  font-weight: 400;
  margin: 0;
}

.h1 {
  font-size: clamp(40px, 6.6vw, 100px);
  line-height: 1.02;
  letter-spacing: -0.02em;
  color: var(--text);
  text-wrap: balance;
  max-width: 17ch;
}
.hero__title { max-width: 17ch; }

.h2 {
  font-size: clamp(28px, 3.4vw, 46px);
  line-height: 1.12;
  letter-spacing: -0.015em;
  color: var(--text);
  text-wrap: balance;
  max-width: 24ch;
}
.h2--sm {
  font-size: clamp(24px, 2.8vw, 36px);
  line-height: 1.15;
  max-width: none;
}

.h3 {
  font-size: clamp(18px, 2.2vw, 30px);
  line-height: 1.18;
  color: var(--text);
  text-wrap: balance;
}

.lede {
  font-size: clamp(16px, 1.4vw, 19px);
  line-height: 1.72;
  color: var(--text-muted);
  max-width: 52ch;
}
.lede--wide { max-width: 60ch; }
.h1 + .lede,
.h2 + .lede { margin-top: clamp(20px, 3vh, 28px); }
.lede + .tiles,
.lede + .notfound__exits { margin-top: clamp(30px, 5vh, 52px); }

.prose {
  font-size: 16.5px;
  line-height: 1.75;
  color: var(--text-muted);
  max-width: 64ch;
}
.prose p + p { margin-top: 0.9em; }
.dim { color: var(--text-dim); }

.eyebrow {
  display: flex;
  align-items: center;
  gap: 12px;
  flex-wrap: wrap;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.2em;
  text-transform: uppercase;
  color: var(--text-dim);
  margin: 0 0 22px;
}
.eyebrow--amber { color: var(--amber); letter-spacing: 0.18em; }
.eyebrow--cyan { color: var(--cyan); }
.eyebrow__brand { color: var(--amber); }
.eyebrow__rule {
  width: 46px;
  height: 1px;
  background: var(--hairline-strong);
}

/* --- layout --- */

.wrap {
  max-width: var(--container);
  margin: 0 auto;
  padding-inline: var(--pad-inline);
}

.section {
  padding-block: var(--section-y);
  border-bottom: 1px solid var(--hairline-soft);
  position: relative;
  overflow: hidden;
}
.section--deep { background: var(--ink-deep); }
.section--paper {
  background: var(--paper);
  color: var(--ink-on-paper);
  border-bottom-color: var(--hairline-paper);
}
.section--flush-top { padding-top: clamp(36px, 7vh, 80px); }
.section--hero-tight { padding-block: clamp(48px, 10vh, 116px); }

.split {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: clamp(24px, 5vw, 72px);
  align-items: end;
}
.split--even { align-items: start; }

.measure { max-width: 62ch; }

.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;
}

.skip-link {
  position: absolute;
  left: 12px;
  top: -60px;
  z-index: 100;
  background: var(--paper);
  color: var(--ink);
  padding: 10px 16px;
  font: 500 12px/1 var(--font-mono);
  transition: top 0.15s ease;
}
.skip-link:focus { top: 12px; color: var(--ink); }

/* --- watermark: a quiet reference mark that stays inside the page bounds
       (never bleeding past the edge — a v1 correction we keep) --- */
.watermark {
  position: absolute;
  z-index: 0;
  pointer-events: none;
  opacity: 0.05;
  width: min(38vw, 460px);
  height: auto;
  right: clamp(16px, 4vw, 64px);
  top: 8%;
}
.wrap,
.section > .wrap { position: relative; z-index: 1; }

@media (prefers-reduced-motion: no-preference) {
  .watermark--drift { animation: tau-drift 22s ease-in-out infinite; }
}

@keyframes tau-drift {
  0%, 100% { transform: translate3d(0, 0, 0) rotate(0deg); }
  50% { transform: translate3d(0, -14px, 0) rotate(-0.6deg); }
}

/* 03-components.css */
/* ============================ header / footer ============================ */

.site-header {
  position: sticky;
  top: 0;
  z-index: 60;
  background: rgba(25, 24, 23, 0.82);
  backdrop-filter: blur(14px);
  -webkit-backdrop-filter: blur(14px);
  border-bottom: 1px solid var(--hairline-soft);
}
.site-header__bar {
  display: flex;
  align-items: center;
  gap: 22px;
  padding-block: 13px;
}
.wordmark {
  display: flex;
  align-items: center;
  gap: 11px;
  color: var(--text);
  margin-right: auto;
}
.wordmark:hover { color: var(--text); }
.wordmark__mark { width: 26px; height: 26px; opacity: 0.92; }
.wordmark__text {
  font-family: var(--font-display);
  font-size: 17px;
  letter-spacing: 0.01em;
}
.wordmark__tag {
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--text-dim);
  border-left: 1px solid var(--hairline-strong);
  padding-left: 11px;
}
.site-nav {
  display: flex;
  align-items: center;
  gap: 22px;
  font-size: 14px;
  color: var(--text-muted);
}
.site-nav a { color: var(--text-muted); }
.site-nav a:hover,
.site-nav a[aria-current="page"] { color: var(--amber); }
.site-header__cta {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  border: 1px solid var(--hairline-strong);
  padding: 9px 16px;
  color: var(--text-muted);
  white-space: nowrap;
}
.site-header__cta:hover { border-color: var(--amber); color: var(--amber); }

@media (max-width: 720px) {
  .site-header__cta { display: none; }
  .site-header__bar { gap: 14px; flex-wrap: wrap; }
  .site-nav { gap: 16px; font-size: 13px; }
  .wordmark__tag { display: none; }
}

.site-footer {
  background: var(--ink-well);
  border-top: 1px solid var(--hairline);
}
.site-footer__grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(190px, 1fr));
  gap: clamp(24px, 4vw, 56px);
  padding-top: clamp(44px, 7vh, 76px);
  padding-bottom: 26px;
}
.site-footer__brand { display: flex; flex-direction: column; gap: 14px; }
.site-footer__brand .wordmark { margin-right: 0; }
.footer-tagline { font-size: 14.5px; line-height: 1.6; color: var(--text-dim); max-width: 30ch; margin: 0; }
.footer-email { font-family: var(--font-mono); font-size: 12px; color: var(--cyan); }
.footer-col__h {
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--text-faint);
  margin: 0 0 16px;
}
.footer-col ul { list-style: none; margin: 0; padding: 0; display: flex; flex-direction: column; gap: 11px; }
.footer-col li { font-size: 14.5px; color: var(--text-muted); }
.site-footer__bar {
  display: flex;
  flex-wrap: wrap;
  gap: 14px;
  justify-content: space-between;
  padding-block: 18px 34px;
  border-top: 1px solid var(--hairline-soft);
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--text-faint);
}
.site-footer__bar a { color: var(--text-faint); }
.site-footer__bar a:hover { color: var(--amber); }

/* ================================ buttons ================================ */

.btn {
  display: inline-flex;
  align-items: center;
  justify-content: space-between;
  gap: 18px;
  padding: 16px 20px;
  font-size: 15px;
  border: 1px solid transparent;
}
.btn .arrow { font-family: var(--font-mono); }
.btn--primary { background: var(--paper); color: var(--ink); }
.btn--primary:hover { background: var(--amber); color: var(--ink); }
.btn--ghost { border-color: var(--hairline-strong); color: var(--text); }
.btn--ghost:hover { border-color: var(--cyan); color: var(--cyan); }
.btn--inline { justify-self: start; align-self: center; }

/* ================================= hero ================================= */

.hero {
  min-height: 88vh;
  display: flex;
  align-items: center;
  border-bottom: 1px solid var(--hairline-soft);
  position: relative;
  overflow: hidden;
}
.hero__wm {
  width: min(48vw, 560px);
  right: clamp(16px, 4vw, 72px);
  top: 6%;
  opacity: 0.055;
}
.hero__inner { padding-block: clamp(72px, 12vh, 140px); width: 100%; }
.eyebrow--hero { margin-bottom: 30px; letter-spacing: 0.2em; }

.hero__body {
  display: grid;
  grid-template-columns: minmax(0, 1.15fr) minmax(0, 0.85fr);
  gap: clamp(24px, 5vw, 72px);
  align-items: end;
  margin-top: clamp(36px, 6vh, 64px);
  border-top: 1px solid rgba(233, 231, 226, 0.12);
  padding-top: 26px;
}
.hero__cta { display: flex; flex-direction: column; gap: 10px; }
@media (max-width: 760px) {
  .hero__body { grid-template-columns: 1fr; }
}

/* ========================== pillars / tiles ============================= */

.pillars { padding-block: 0; border: 0; }
.tiles {
  display: grid;
  gap: 1px;
  background: rgba(233, 231, 226, 0.12);
  border-block: 1px solid rgba(233, 231, 226, 0.12);
}
.tiles--4 { grid-template-columns: repeat(auto-fit, minmax(160px, 1fr)); }
.pillars .tiles { margin-top: clamp(40px, 7vh, 76px); }
.tile { background: var(--ink); padding: 18px 20px 20px; }
.pillar { display: flex; flex-direction: column; }
.pillar__n {
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.18em;
  color: var(--cyan);
  margin-bottom: 10px;
}
.pillar__t { font-family: var(--font-display); font-size: 15px; letter-spacing: 0.01em; color: var(--text); }
.pillar__d { font-size: 13.5px; color: var(--text-dim); margin-top: 6px; line-height: 1.5; }

.section--deep .tile { background: var(--ink-deep); }
.fact__k,
.prereq__k {
  display: block;
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--text-dim);
  margin-bottom: 8px;
}
.fact__v { font-family: var(--font-display); font-size: 16px; color: var(--text); }
.course-facts { margin-top: clamp(34px, 6vh, 56px); }

/* ===================== exploration (home demo section) ================= */

.exploration .measure { position: relative; z-index: 1; }
.ex-demo {
  display: inline-block;
  margin: 0 0 18px;
  padding: 5px 10px;
  border: 1px solid rgba(224, 182, 117, 0.4);
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--amber);
}

.ex-shell {
  margin-top: clamp(30px, 5vh, 52px);
  border: 1px solid var(--hairline);
  background: var(--panel-alt);
}

/* step rail */
.ex-rail {
  display: flex;
  overflow-x: auto;
  border-bottom: 1px solid var(--hairline);
  scrollbar-width: none;
}
.ex-rail::-webkit-scrollbar { display: none; }
.ex-rail__item {
  flex: 1 0 auto;
  display: flex;
  align-items: baseline;
  gap: 8px;
  padding: 13px 16px;
  background: transparent;
  border: 0;
  border-right: 1px solid var(--hairline-soft);
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-faint);
  cursor: pointer;
  white-space: nowrap;
  transition: color 0.2s, background 0.2s;
}
.ex-rail__item:hover { color: var(--text-muted); }
.ex-rail__item[aria-current="step"] { color: var(--amber); background: rgba(224, 182, 117, 0.06); }
.ex-rail__n { color: inherit; }
.no-js .ex-rail { display: none; }

/* body: narrative + persistent figure */
.ex-body {
  display: grid;
  grid-template-columns: minmax(0, 1fr) minmax(0, 1.02fr);
  gap: 1px;
  background: var(--hairline);
}
.ex-narrative { background: var(--ink); padding: clamp(22px, 3vw, 36px); }
.ex-figure { background: var(--ink); padding: clamp(18px, 3vw, 30px); }

.ex-step__k {
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--text-dim);
  margin: 0 0 14px;
}
.ex-step__h {
  font-family: var(--font-display);
  font-size: clamp(19px, 2vw, 26px);
  line-height: 1.16;
  color: var(--text);
  margin: 0 0 12px;
}
.ex-q {
  font-size: clamp(16px, 1.5vw, 19px);
  line-height: 1.5;
  color: var(--text);
  margin: 0 0 14px;
}
.ex-q--tension { color: var(--amber); }

.ex-known { list-style: none; margin: 18px 0 0; padding: 0; display: flex; flex-wrap: wrap; gap: 1px; background: var(--hairline); border: 1px solid var(--hairline); }
.ex-known li {
  flex: 1 1 130px;
  background: var(--panel);
  padding: 10px 12px;
  display: flex;
  flex-direction: column;
  gap: 3px;
}
.ex-known span { font-family: var(--font-mono); font-size: 9.5px; letter-spacing: 0.12em; text-transform: uppercase; color: var(--text-dim); }
.ex-known b { font-family: var(--font-mono); font-size: 16px; font-weight: 500; color: var(--text); }

.ex-pair { margin: 18px 0 0; display: grid; gap: 1px; background: var(--hairline); border: 1px solid var(--hairline); }
.ex-pair > div { background: var(--panel-soft); padding: 12px 14px; }
.ex-pair dt {
  font-family: var(--font-mono);
  font-size: 9.5px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--cyan);
  margin-bottom: 5px;
}
.ex-pair div:last-child dt { color: var(--amber); }
.ex-pair dd { margin: 0; font-size: 14px; line-height: 1.5; color: var(--text-muted); }

.ex-formal { margin-top: 18px; border-left: 2px solid var(--amber); background: var(--panel); padding: 18px clamp(14px, 2vw, 22px); }
.ex-formal__eq { overflow-x: auto; overflow-y: hidden; padding: 2px 0 8px; }
.ex-formal .prose { font-size: 14.5px; }

/* decision */
.ex-choice { display: flex; flex-direction: column; gap: 1px; margin: 4px 0 0; background: var(--hairline); border: 1px solid var(--hairline); }
.ex-opt {
  background: var(--panel);
  padding: 13px 15px;
  display: flex;
  align-items: flex-start;
  gap: 12px;
  cursor: pointer;
  transition: background 0.18s;
}
.ex-opt:hover { background: #262523; }
.ex-opt input { position: absolute; opacity: 0; width: 1px; height: 1px; }
.ex-opt__box { flex: none; width: 15px; height: 15px; margin-top: 2px; border: 1px solid var(--hairline-strong); border-radius: 50%; transition: border-color 0.18s, box-shadow 0.18s; }
.ex-opt input:checked + .ex-opt__box { border-color: var(--amber); box-shadow: inset 0 0 0 3.5px var(--amber); }
.ex-opt input:focus-visible + .ex-opt__box { outline: 2px solid var(--cyan); outline-offset: 2px; }
.ex-opt__label { font-size: 14.5px; line-height: 1.45; color: var(--text-muted); }
.ex-opt input:checked ~ .ex-opt__label { color: var(--text); }

.ex-feedback { margin: 14px 0 0; font-size: 14px; line-height: 1.6; color: var(--text-muted); }
.ex-feedback__correct,
.ex-feedback__incorrect,
.ex-feedback__note { display: none; }
.ex-feedback__note { display: none; margin-top: 6px; color: var(--text-dim); }
.ex-feedback[data-state="correct"] .ex-feedback__correct,
.ex-feedback[data-state="incorrect"] .ex-feedback__incorrect,
.ex-feedback[data-state="correct"] .ex-feedback__note,
.ex-feedback[data-state="incorrect"] .ex-feedback__note { display: block; }
.ex-feedback[data-state="correct"] { color: var(--text); }
/* no-JS feedback via :has() */
.no-js .ex-choice:has(input[data-correct="true"]:checked) ~ .ex-feedback .ex-feedback__correct { display: block; }
.no-js .ex-choice:has(input:checked:not([data-correct="true"])) ~ .ex-feedback .ex-feedback__incorrect { display: block; }

/* validation checks */
.ex-checks { list-style: none; margin: 0; padding: 0; display: flex; flex-direction: column; gap: 10px; }
.ex-check { display: flex; gap: 12px; align-items: flex-start; font-size: 14px; line-height: 1.5; color: var(--text-muted); }
.ex-check__mark { flex: none; width: 16px; height: 16px; margin-top: 1px; border: 1px solid var(--hairline-strong); position: relative; }
.ex-check[data-check="pass"] .ex-check__mark { border-color: var(--cyan); }
.ex-check[data-check="pass"] .ex-check__mark::after { content: ""; position: absolute; left: 4px; top: 1px; width: 5px; height: 9px; border: solid var(--cyan); border-width: 0 1.5px 1.5px 0; transform: rotate(45deg); }
.ex-check[data-check="fail"] .ex-check__mark { border-color: var(--amber); }
.ex-check[data-check="fail"] .ex-check__mark::after { content: ""; position: absolute; inset: 4px; border-top: 1.5px solid var(--amber); transform: rotate(0); }
.ex-check__text em { display: block; margin-top: 3px; font-style: normal; color: var(--text-dim); font-size: 13px; }

.ex-transfer { margin-top: 22px; border-top: 1px solid var(--hairline); padding-top: 16px; }
.ex-transfer__h {
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--text-dim);
  margin: 0 0 12px;
}
.ex-t { display: grid; grid-template-columns: minmax(0, 0.5fr) minmax(0, 1fr); gap: 14px; padding: 9px 0; border-top: 1px solid var(--hairline-soft); }
.ex-t:first-of-type { border-top: 0; }
.ex-t__field { font-family: var(--font-mono); font-size: 11px; letter-spacing: 0.1em; text-transform: uppercase; color: var(--cyan); }
.ex-t__op { font-size: 14px; line-height: 1.45; color: var(--text-muted); }

/* the persistent morphing figure */
.ex-figure__frame { position: relative; }
.ex-fig-svg { width: 100%; height: auto; display: block; background: var(--ink-well); border: 1px solid var(--hairline-soft); }
.ex-fig-svg text { font-family: var(--font-mono); }
.ex-fig-svg .ex-pt {
  transform: translate(var(--table-x), var(--table-y));
  transition: transform 0.7s cubic-bezier(0.4, 0, 0.1, 1);
}
.ex-fig-svg[data-view="plot"] .ex-pt { transform: translate(var(--plot-x), var(--plot-y)); }
.ex-mark { transition: opacity 0.4s; }
.ex-mark--sq { fill: none; stroke: var(--text-dim); stroke-width: 1.3; }
.ex-mark--dot { fill: var(--cyan); opacity: 0; }
.ex-fig-svg[data-view="plot"] .ex-mark--sq { opacity: 0; }
.ex-fig-svg[data-view="plot"] .ex-mark--dot { opacity: 1; }
.ex-pt--cluster .ex-mark--dot { fill: var(--amber); }
.ex-label {
  fill: var(--text-muted);
  font-size: 15px;
  text-anchor: start;
  dominant-baseline: middle;
  transform: translate(22px, 0);
  transition: opacity 0.4s;
}
.ex-value {
  fill: var(--text);
  font-size: 18px;
  text-anchor: end;
  dominant-baseline: middle;
  transform: translate(492px, 0);
  transition: transform 0.6s cubic-bezier(0.4, 0, 0.1, 1);
}
.ex-fig-svg[data-view="plot"] .ex-label { opacity: 0; }
.ex-fig-svg[data-view="plot"] .ex-value { font-size: 14px; transform: translate(0, -15px); text-anchor: middle; }
.ex-fig-svg[data-view="plot"] .ex-pt[data-tier="1"] .ex-value { transform: translate(0, -30px); }
.ex-fig-svg[data-view="plot"] .ex-pt[data-tier="2"] .ex-value { transform: translate(0, -45px); }
.ex-rule { stroke: var(--hairline-soft); stroke-width: 1; transition: opacity 0.4s; }
.ex-fig-svg[data-view="plot"] .ex-rules { opacity: 0; }
.ex-axis { stroke: rgba(233, 231, 226, 0.22); stroke-width: 1; opacity: 0; transition: opacity 0.5s; }
.ex-ticks { opacity: 0; transition: opacity 0.5s; }
.ex-tick line { stroke: rgba(233, 231, 226, 0.22); stroke-width: 1; }
.ex-tick text { fill: var(--text-dim); font-size: 13px; }
.ex-fig-svg[data-view="plot"] .ex-axis,
.ex-fig-svg[data-view="plot"] .ex-ticks { opacity: 1; }
.ex-axis-label { fill: var(--text-dim); font-size: 13px; opacity: 0; transition: opacity 0.5s; }
.ex-fig-svg[data-view="plot"] .ex-axis-label { opacity: 1; }
.ex-band { fill: var(--amber); opacity: 0; transition: opacity 0.5s; }
.ex-center { stroke: var(--amber); stroke-width: 1; stroke-dasharray: 3 4; opacity: 0; transition: opacity 0.5s; }
.ex-center-label { fill: var(--amber); font-size: 15px; opacity: 0; transition: opacity 0.5s; }
.ex-fig-svg.is-reframed .ex-band { opacity: 0.16; }
.ex-fig-svg.is-formal .ex-center,
.ex-fig-svg.is-formal .ex-center-label { opacity: 1; }
.ex-pick { stroke: var(--cyan); stroke-width: 1.6; opacity: 0; transition: opacity 0.4s, transform 0.5s cubic-bezier(0.4, 0, 0.1, 1); }
.ex-fig-svg[data-view="plot"].is-picked .ex-pick { opacity: 0.9; }
.ex-figure__cap {
  margin: 10px 0 0;
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-faint);
}
.ex-figure__nojs { margin-top: 1px; }
.js .ex-figure__nojs { display: none; }

/* controls */
.ex-controls {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 14px;
  padding: 12px 16px;
  border-top: 1px solid var(--hairline);
}
.no-js .ex-controls { display: none; }
.ex-nav {
  background: transparent;
  border: 1px solid var(--hairline-strong);
  color: var(--text-muted);
  padding: 9px 16px;
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  cursor: pointer;
  transition: color 0.18s, border-color 0.18s;
}
.ex-nav:hover:not(:disabled) { color: var(--amber); border-color: var(--amber); }
.ex-nav:disabled { opacity: 0.35; cursor: default; }
.ex-progress { font-family: var(--font-mono); font-size: 11px; letter-spacing: 0.14em; color: var(--text-dim); }
.ex-progress__n { color: var(--amber); font-weight: 500; margin-right: 4px; }

/* JS on: one step at a time */
.js .ex-step { display: none; }
.js .ex-shell[data-step="1"] .ex-step[data-step="1"],
.js .ex-shell[data-step="2"] .ex-step[data-step="2"],
.js .ex-shell[data-step="3"] .ex-step[data-step="3"],
.js .ex-shell[data-step="4"] .ex-step[data-step="4"],
.js .ex-shell[data-step="5"] .ex-step[data-step="5"],
.js .ex-shell[data-step="6"] .ex-step[data-step="6"] { display: block; }

/* JS off: stacked, discrete */
.no-js .ex-step { border-top: 1px solid var(--hairline); padding-top: 22px; margin-top: 22px; }
.no-js .ex-step:first-child { border-top: 0; padding-top: 0; margin-top: 0; }

@media (prefers-reduced-motion: reduce) {
  .ex-fig-svg .ex-pt,
  .ex-value,
  .ex-mark,
  .ex-axis,
  .ex-ticks,
  .ex-rule,
  .ex-band,
  .ex-center,
  .ex-center-label,
  .ex-axis-label { transition: none; }
}

/* =============================== notebook ============================== */

.notebook-section { position: relative; }
.lissajous { width: min(44vw, 520px); right: clamp(16px, 3vw, 56px); top: 8%; opacity: 0.16; }
.measure { position: relative; z-index: 1; }

.notebook {
  margin-top: clamp(34px, 5vh, 56px);
  border: 1px solid var(--hairline);
  background: var(--ink);
  position: relative;
  z-index: 1;
}
.notebook__bar {
  display: flex;
  align-items: center;
  gap: 14px;
  padding: 13px 18px;
  border-bottom: 1px solid var(--hairline);
  background: var(--panel);
}
.dot { width: 8px; height: 8px; border-radius: 50%; background: var(--amber); flex: none; }
.notebook__file { font-family: var(--font-mono); font-size: 11.5px; letter-spacing: 0.08em; color: var(--text-muted); }
.notebook__bar { flex-wrap: wrap; }
.notebook__file { min-width: 0; overflow: hidden; text-overflow: ellipsis; }
.notebook__badge {
  margin-left: auto;
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--text-dim);
  white-space: nowrap;
}
.nb-row { display: grid; grid-template-columns: var(--gutter) minmax(0, 1fr); }
.nb-code { min-width: 0; overflow: hidden; }
.nb-gutter {
  border-right: 1px solid var(--hairline-soft);
  padding-top: 26px;
  text-align: center;
  font-family: var(--font-mono);
  font-size: 10.5px;
  color: var(--text-faint);
}
.nb-cell { padding: 22px clamp(18px, 3vw, 40px) 26px; min-width: 0; }
.nb-cell .h3 { margin-bottom: 12px; }

.nb-math {
  border-left: 2px solid var(--amber);
  background: var(--panel);
  padding: 24px clamp(18px, 3vw, 34px);
  display: flex;
  flex-direction: column;
  gap: 14px;
  overflow-x: auto;
}
.callouts {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(230px, 1fr));
  gap: 1px;
  margin-top: 1px;
  background: rgba(233, 231, 226, 0.12);
}
.callout { background: var(--panel-soft); padding: 16px 18px; }
.callout__label {
  display: block;
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  margin-bottom: 8px;
}
.callout--assume .callout__label { color: var(--cyan); }
.callout--decide .callout__label { color: var(--amber); }
.callout__body { font-size: 14.5px; line-height: 1.55; color: var(--text-muted); }

.nb-code { border: 1px solid var(--hairline); }
.nb-code > summary {
  display: flex;
  align-items: center;
  gap: 12px;
  padding: 12px 16px;
  cursor: pointer;
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--text-dim);
  list-style: none;
}
.nb-code > summary::-webkit-details-marker { display: none; }
.nb-code > summary:hover { border-color: var(--cyan); color: var(--cyan); }
.nb-code__sign::before { content: "+"; color: var(--cyan); }
.nb-code[open] .nb-code__sign::before { content: "\2212"; }
.nb-code__note {
  margin-left: auto;
  text-transform: none;
  letter-spacing: 0.02em;
  color: var(--text-faint);
  font-size: 10.5px;
}
.nb-code .lbl-open { display: none; }
.nb-code[open] .lbl-closed { display: none; }
.nb-code[open] .lbl-open { display: inline; }

.code {
  margin: 1px 0 0;
  background: var(--ink-well);
  border: 1px solid var(--hairline-soft);
  padding: 20px clamp(16px, 2vw, 26px);
  overflow-x: auto;
  font-family: var(--font-mono);
  font-size: 13px;
  line-height: 1.75;
  color: #cfcbc2;
  white-space: pre;
}
.tok-kw { color: var(--cyan); }
.tok-num { color: var(--amber); }
.tok-str { color: var(--amber); }
.tok-comment { color: var(--text-faint); }

.chips,
.lab__metrics,
.space__chips {
  display: flex;
  flex-wrap: wrap;
  gap: 8px;
  margin-top: 14px;
  font-family: var(--font-mono);
  font-size: 10.5px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--text-dim);
}
.chip,
.lab__metrics span,
.space__chips span { border: 1px solid var(--hairline-strong); padding: 6px 11px; }

.transfers { display: flex; flex-wrap: wrap; gap: 1px; margin-top: 14px; background: rgba(233, 231, 226, 0.12); }
.transfer { background: var(--panel-soft); padding: 15px 18px; flex: 1 1 190px; }
.transfer__field {
  display: block;
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--cyan);
  margin-bottom: 7px;
}
.transfer__what { display: block; font-size: 14.5px; color: var(--text); }
.transfer__q { display: block; font-size: 13.5px; color: var(--text-dim); margin-top: 4px; }

/* ================================ figures ============================== */

.fig { margin: 0; }
.fig-cap {
  display: flex;
  justify-content: space-between;
  gap: 14px;
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--text-faint);
  margin-bottom: 10px;
}
.fig-svg {
  width: 100%;
  height: auto;
  display: block;
  background: var(--ink-well);
  border: 1px solid var(--hairline-soft);
  padding: 10px;
}
.fig-svg--xy { max-width: 640px; }
.fig-svg--nf { max-width: 560px; }
.fig-axis { stroke: rgba(233, 231, 226, 0.22); stroke-width: 1; }
.fig-grid { stroke: rgba(233, 231, 226, 0.07); stroke-width: 1; }
.fig-tick { fill: var(--text-dim); font-family: var(--font-mono); font-size: 16px; }
.fig-obs { fill: none; stroke: var(--cyan); stroke-width: 1.4; }
.fig-model { fill: none; stroke: var(--amber); stroke-width: 2; }
.nf-branch { fill: none; stroke: var(--cyan); stroke-width: 2; }
.nf-gap { stroke: rgba(224, 182, 117, 0.45); stroke-width: 1; stroke-dasharray: 4 5; }
.nf-hole { fill: var(--ink-well); stroke: var(--amber); stroke-width: 2; }
.nf-label { fill: var(--amber); font-family: var(--font-mono); font-size: 18px; }
.nf-halo { fill: none; stroke: var(--amber); stroke-width: 1.5; }
.fig-eq { margin-top: 16px; color: var(--text-muted); overflow-x: auto; overflow-y: hidden; padding: 4px 0; }

@media (prefers-reduced-motion: no-preference) {
  .fig-model--draw { stroke-dasharray: 1; stroke-dashoffset: 1; animation: fig-draw 2.2s var(--reveal-ease) forwards; }
  .nf-halo { animation: nf-halo 2.4s ease-out infinite; }
}
@keyframes fig-draw { to { stroke-dashoffset: 0; } }
@keyframes nf-halo {
  0% { stroke-opacity: 0.55; transform: scale(1); transform-origin: center; }
  100% { stroke-opacity: 0; transform: scale(2.4); transform-origin: center; }
}

.spark-svg { width: 100%; height: auto; display: block; }
.spark { fill: none; }
.spark--primary { stroke: var(--amber); stroke-width: 1.6; }
.spark--second { stroke: rgba(111, 192, 216, 0.55); stroke-width: 1; }
.spark--trend { stroke: rgba(224, 182, 117, 0.4); stroke-width: 1.2; }
.spark-resid { fill: var(--amber); }

/* ============================= areas (paper) =========================== */

.section--paper .eyebrow { color: var(--ink-on-paper-dim); }
.section--paper .h2 { color: var(--ink-on-paper); }
.section--paper .lede,
.section--paper .prose { color: var(--ink-on-paper-muted); }

.rows { margin-top: clamp(34px, 6vh, 60px); border-top: 1px solid var(--hairline-paper); }
.row {
  display: grid;
  grid-template-columns: 54px minmax(0, 1.1fr) minmax(0, 1.4fr) 28px;
  gap: clamp(12px, 3vw, 34px);
  align-items: baseline;
  padding: 22px 6px;
  border-bottom: 1px solid var(--hairline-paper);
  transition: background 0.25s, padding-left 0.25s;
}
.row:hover { background: rgba(25, 24, 23, 0.05); padding-left: 16px; }
.row__n { font-family: var(--font-mono); font-size: 11px; color: var(--ink-on-paper-dim); }
.row__t { font-family: var(--font-display); font-size: clamp(17px, 1.7vw, 22px); color: var(--ink-on-paper); }
.row__d { font-size: 15px; line-height: 1.55; color: var(--ink-on-paper-muted); }
.row__arrow { font-family: var(--font-mono); font-size: 13px; color: var(--ink-on-paper-dim); text-align: right; }
@media (max-width: 640px) {
  .row { grid-template-columns: 34px 1fr; }
  .row__d { grid-column: 2; }
  .row__arrow { display: none; }
}

/* ================================ spaces =============================== */

.spaces {
  margin-top: clamp(30px, 5vh, 52px);
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(300px, 1fr));
  gap: 1px;
  background: rgba(233, 231, 226, 0.12);
}
.space {
  background: var(--panel);
  padding: clamp(26px, 4vw, 42px);
  display: flex;
  flex-direction: column;
  gap: 16px;
  color: var(--text);
}
.space:hover { background: #262523; color: var(--text); }
.space__kick {
  display: flex;
  justify-content: space-between;
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.18em;
  text-transform: uppercase;
}
.space--amber .space__kick { color: var(--amber); }
.space--cyan .space__kick { color: var(--cyan); }
.space__kick .dim { color: var(--text-faint); }
.space .prose { font-size: 16px; line-height: 1.7; max-width: 44ch; }
.space__cta { margin-top: auto; font-size: 14.5px; }
.space--amber .space__cta { color: var(--amber); }
.space--cyan .space__cta { color: var(--cyan); }
.space__chips { margin-top: 0; }

/* ============================ course / labs ============================ */

.course-hero,
.labs-hero { border-bottom: 1px solid var(--hairline-soft); }
.course-hero__wm { width: min(44vw, 480px); left: clamp(16px, 4vw, 64px); right: auto; top: 4%; opacity: 0.05; }
.labs-hero__wm { width: min(40vw, 440px); right: clamp(16px, 4vw, 64px); top: 4%; opacity: 0.05; }

.split--even .h2--sm { margin-bottom: 20px; }
.outcomes { list-style: none; margin: 0; padding: 0; }
.outcome {
  display: grid;
  grid-template-columns: 26px minmax(0, 1fr);
  gap: 14px;
  padding: 15px 0;
  border-bottom: 1px solid rgba(233, 231, 226, 0.12);
  font-size: 16px;
  line-height: 1.6;
  color: #cfcbc2;
}
.outcome__n { font-family: var(--font-mono); font-size: 11px; color: var(--amber); }

.thread {
  border-left: 2px solid var(--cyan);
  background: var(--panel);
  padding: 24px clamp(18px, 3vw, 30px);
  margin-bottom: 20px;
}
.thread__eq { overflow-x: auto; overflow-y: hidden; padding: 4px 0; }
.thread__note { margin: 16px 0 0; font-size: 15px; line-height: 1.65; color: var(--text-dim); }

.module-head {
  display: flex;
  flex-wrap: wrap;
  gap: 18px;
  align-items: baseline;
  justify-content: space-between;
  margin-bottom: clamp(28px, 5vh, 46px);
}
.module-head__meta {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--text-dim);
}
.modules { border-top: 1px solid var(--hairline); }
.module {
  display: grid;
  grid-template-columns: 52px minmax(0, 1fr) minmax(0, 1.3fr) auto;
  gap: clamp(12px, 3vw, 30px);
  align-items: baseline;
  padding: 20px 6px;
  border-bottom: 1px solid var(--hairline);
  transition: background 0.25s, padding-left 0.25s;
}
.module:hover { background: rgba(233, 231, 226, 0.045); padding-left: 16px; }
.module__n { font-family: var(--font-mono); font-size: 11px; color: var(--text-faint); }
.module__t { font-family: var(--font-display); font-size: clamp(16px, 1.6vw, 20px); color: var(--text); }
.module__d { font-size: 15px; line-height: 1.55; color: var(--text-dim); }
.module__tag {
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--cyan);
  white-space: nowrap;
}
@media (max-width: 720px) {
  .module { grid-template-columns: 32px 1fr; }
  .module__d { grid-column: 2; }
  .module__tag { grid-column: 2; }
}

.prereqs,
.prereq { display: flex; flex-direction: column; }
.prereqs { gap: 1px; background: var(--hairline-paper); }
.section--paper .prereq { background: var(--paper); padding: 18px 20px; }
.section--paper .prereq__k { color: var(--ink-on-paper-dim); }
.prereq__v { font-size: 15.5px; line-height: 1.55; color: var(--ink-on-paper); }

.labs-grid {
  display: grid;
  grid-template-columns: repeat(auto-fill, minmax(300px, 1fr));
  gap: 1px;
  background: rgba(233, 231, 226, 0.12);
}
.lab {
  background: var(--panel);
  padding: clamp(22px, 3vw, 32px);
  display: flex;
  flex-direction: column;
  gap: 14px;
}
.lab:hover { background: #262523; }
.lab__meta {
  display: flex;
  justify-content: space-between;
  font-family: var(--font-mono);
  font-size: 10px;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--cyan);
}
.lab__meta .dim { color: var(--text-faint); }
.lab__fig { border: 1px solid var(--hairline-soft); background: var(--ink-well); padding: 8px 6px; }
.lab__cap {
  font-family: var(--font-mono);
  font-size: 11px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--text-muted);
  margin-top: -4px;
}
.lab .prose { font-size: 15px; line-height: 1.62; color: var(--text-dim); }
.lab__metrics { margin-top: auto; font-size: 10px; letter-spacing: 0.08em; }
.lab__metrics span { padding: 5px 9px; }

/* ================================= 404 ================================ */

.notfound { min-height: 78vh; display: flex; align-items: center; }
.notfound__wm { right: clamp(16px, 4vw, 64px); bottom: 4%; top: auto; width: min(42vw, 460px); opacity: 0.05; }
.notfound__exits { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 32px; }
.notfound__exits .btn { flex: 0 1 auto; }
.notfound__fig .fig-svg { padding: 20px clamp(16px, 2.5vw, 28px) 14px; }

/* ================================ math ================================ */

.katex { font-size: 1.06em; }
.katex-display { margin: 0; }
.math--display { display: block; overflow-x: auto; overflow-y: hidden; padding: 4px 0; }
.math--inline { white-space: nowrap; }

/* ============================= responsive ============================ */

@media (max-width: 720px) {
  :root { --gutter: 30px; }
  .nb-gutter { font-size: 9px; padding-top: 22px; }
  .nb-cell { padding: 18px 16px 22px; }
  .nb-math { padding: 18px 14px; }
  .notebook__badge { flex-basis: 100%; margin-left: 0; }
  .nb-code > summary { flex-wrap: wrap; }
  .nb-code__note { flex-basis: 100%; margin-left: 18px; }
  .notfound { min-height: 0; }

  .ex-body { grid-template-columns: 1fr; }
  .ex-figure { border-top: 1px solid var(--hairline); }
  .js .ex-body { display: flex; flex-direction: column; }
  .js .ex-figure { order: 2; }
  .js .ex-narrative { order: 1; }
  .ex-rail__item { padding: 11px 12px; }
  .ex-t { grid-template-columns: 1fr; gap: 4px; }
}

@media (max-width: 460px) {
  .transfer { flex: 1 1 100%; }
  .ex-value { font-size: 17px; }
  .ex-tick text { font-size: 14px; }
}

/* =============================== reveal =============================== */

.reveal { will-change: opacity, transform; }
.js .reveal {
  opacity: 0;
  transform: translateY(22px);
  transition: opacity 0.85s var(--reveal-ease), transform 0.85s var(--reveal-ease);
}
.js .reveal.is-visible { opacity: 1; transform: none; }
@media (prefers-reduced-motion: reduce) {
  .js .reveal { opacity: 1; transform: none; transition: none; }
}