/* /learn, the Primer: its own sheet, loaded after site.css by learn.html only.
   The page is the longest in the library, so the layout's job is the read:
   an answer first, a contents list, a bar that follows the reader, and ten
   parts that each take their own shape. A drawing here explains a mechanism
   or is not drawn. Script: scripts/primer.js. With that script absent every
   part is visible, every fold is open and every link still jumps. */

html:has(body.primer) {
  --hc-nav-h: 64px;            /* fallback; the script sets the real header height */
  --hc-bar-h: 52px;
  /* every jump, anchor and Tab or Shift+Tab stop lands below the header and the bar */
  scroll-padding-top: calc(var(--hc-nav-h) + var(--hc-bar-h) + 12px);
}
body.primer { background: var(--white); }
.primer {
  --pr-ease: cubic-bezier(.16, 1, .3, 1);
  --pr-gut: clamp(20px, 4vw, 56px);
  --pr-stick: calc(var(--hc-nav-h) + var(--hc-bar-h) + 28px);
}

/* ============ GROUND RULES ============ */
.primer main { overflow-x: clip; }
.pr-wrap { max-width: calc(1240px + 2 * var(--pr-gut)); margin-inline: auto; padding-inline: var(--pr-gut); }
/* text fills its column; the column sets the measure */
.primer main p { max-width: none; margin: 0; }
.primer main a:not(.btn) { border-bottom: 0; }
.primer main :is(h1, h2, h3) { max-width: none; text-wrap: wrap; }
.primer main h2 {
  font-family: var(--font-display); font-weight: 300; color: var(--ink);
  font-size: clamp(1.9rem, 3.3vw, 3rem); line-height: 1.1; letter-spacing: -.01em;
  margin: 0 0 clamp(24px, 3.4vw, 48px);
}
/* a heading that has to wrap breaks where the styling changes */
.primer main :is(h1, h2, h3) > :is(.h-lead, em) { display: inline-block; }
.primer main :is(h1, h2, h3) em { font-style: italic; color: var(--accent-blue); }
.primer main :is(a, .btn, summary, button):focus-visible { outline: 2px solid var(--accent-blue); outline-offset: 3px; border-radius: 4px; }
.primer :is(.pr-moa, .pr-cta) :is(a, .btn):focus-visible { outline-color: var(--accent-ice); }
/* a part that receives focus after a jump is not itself a control */
.primer main :is(h1, h2, h3, section, li, div)[tabindex="-1"]:focus { outline: none; }

.primer main > section { padding-block: clamp(52px, 7vw, 108px); }
.primer main > section + section:not(.pr-moa, .pr-why, .pr-cta) { border-top: 1px solid var(--border); }
.primer main > .pr-moa + section, .primer main > .pr-why + section { border-top: 0; }

/* running text */
.pr-prose > p, .pr-more > p { font-size: 18px; line-height: 1.7; color: var(--ink-soft); }
.primer main .pr-prose > * + * { margin-top: 20px; }
.primer main .pr-more > p + p { margin-top: 20px; }
.pr-prose em { font-style: italic; }
.pr-prose strong { font-weight: 600; color: var(--ink); }
.primer main .pr-stand { font-family: var(--font-display); font-size: clamp(1.5rem, 2.2vw, 2rem); line-height: 1.2; color: var(--accent-blue-hover); }

/* a term this page's glossary defines */
.pr-term { color: inherit; text-decoration: underline dotted; text-decoration-color: var(--accent-blue); text-decoration-thickness: 1.5px; text-underline-offset: 4px; transition: color 200ms, text-decoration-color 200ms; }
.pr-term:hover { color: var(--accent-blue-hover); text-decoration-style: solid; }
.pr-term dfn { font-style: normal; }
.pr-term strong { font-weight: 600; }

/* the limit each of the first four parts ends on */
.primer main .pr-limit { border-left: 3px solid var(--accent-blue); padding: 2px 0 2px 20px; font-size: 18px; line-height: 1.65; color: var(--ink); }
.pr-limit strong { font-weight: 600; }

/* a margin note */
.pr-note { border: 1px solid var(--border-strong); border-radius: 10px; padding: 20px 22px 22px; }
.pr-note > strong { display: block; font-family: var(--font-display); font-weight: 400; font-size: 1.45rem; line-height: 1.2; color: var(--ink); margin-bottom: 8px; }
.pr-note p { font-size: 16px; line-height: 1.6; color: var(--ink-muted); }
.pr-note em { font-style: italic; }
.pr-note a, .pr-faq__a a { color: var(--accent-blue-hover); text-decoration: underline; text-underline-offset: 3px; text-decoration-thickness: 1px; transition: color 200ms, text-decoration-thickness 200ms; }
.pr-note a:hover, .pr-faq__a a:hover { color: var(--accent-blue); text-decoration-thickness: 2px; }

/* the onward link: the arrow leans the way it points */
.pr-go { display: inline-flex; align-items: center; gap: 10px; min-height: 44px; font-size: 16px; font-weight: 600; color: var(--accent-blue-hover); text-decoration: underline; text-decoration-color: transparent; text-underline-offset: 5px; transition: color 200ms, text-decoration-color 260ms; }
.pr-go span { display: inline-block; transition: transform 360ms var(--pr-ease); }
.pr-go:hover { color: var(--accent-blue); text-decoration-color: currentColor; }
.pr-go:hover span { transform: translateX(6px); }
.pr-next { display: flex; flex-wrap: wrap; align-items: baseline; gap: 0 28px; margin-top: clamp(32px, 4vw, 56px); padding-top: 14px; border-top: 1px solid var(--border); }
.pr-next__k { font-size: 15px; color: var(--ink-muted); }
.pr-next ul { list-style: none; margin: 0; padding: 0; display: flex; flex-wrap: wrap; gap: 0 32px; }
.pr-moa .pr-next { border-top-color: rgba(255, 255, 255, .2); }
.pr-moa .pr-next__k { color: rgba(255, 255, 255, .74); }
.pr-moa .pr-go { color: #c9def2; }
.pr-moa .pr-go:hover { color: #fff; }
.pr-why .pr-next { border-top-color: var(--border-strong); }

/* ============ FOLDS (native details) ============
   Shipped open. On a phone the script closes the ones a reader can skip; on a
   desktop "Read more" is not shown and a folding heading is just a heading. */
.primer details > summary { list-style: none; }
.primer details > summary::-webkit-details-marker { display: none; }
.pr-chev { width: 20px; height: 20px; flex: none; color: var(--accent-blue-hover); transition: transform 320ms var(--pr-ease); display: none; }
.primer details[open] > summary .pr-chev { transform: rotate(180deg); }
.pr-more > summary { display: none; }
.pr-more__less, .pr-more[open] > summary .pr-more__more { display: none; }
.pr-more[open] > summary .pr-more__less { display: inline; }
.pr-fold > summary { display: flex; align-items: center; justify-content: space-between; gap: 14px; cursor: default; }
.pr-fold > summary h3 { margin: 0; }
@keyframes pr-unfold { from { opacity: 0; transform: translateY(-6px); } }

/* ============ REVEALS ============
   Hidden only once the script has said it is running (pr-js on <html>), so
   with no script nothing is ever hidden. Each part comes in its own way;
   the ones named below keep their box and move what is inside it. */
.pr-js [data-r] { transition: opacity 620ms ease, transform 820ms var(--pr-ease); }
.pr-js [data-r]:not(.is-in) { opacity: 0; transform: translateY(18px); }
.pr-js [data-r="left"]:not(.is-in) { transform: translateX(-28px); }
.pr-js [data-r="right"]:not(.is-in) { transform: translateX(28px); }
.pr-js :is([data-r="left"], [data-r="right"]) { transition-delay: calc(var(--i, 0) * 40ms); }
.pr-js :is([data-r="draw"], [data-r="see"], [data-r="gauge"], [data-r="strike"], [data-r="cross"], [data-r="doc"]):not(.is-in) { opacity: 1; transform: none; }

@keyframes pr-up { from { opacity: 0; transform: translateY(22px); } }
@keyframes pr-draw { from { stroke-dashoffset: 1; opacity: 0; } 12% { opacity: 1; } to { stroke-dashoffset: 0; opacity: 1; } }
@keyframes pr-pop { from { transform: scale(0); opacity: 0; } 70% { transform: scale(1.18); opacity: 1; } }
@keyframes pr-fade { from { opacity: 0; } }

/* ============ HERO ============ */
.primer main > .pr-hero { padding-block: clamp(28px, 4vw, 60px) clamp(40px, 5vw, 76px); }
.pr-hero__h1 { font-family: var(--font-display); font-weight: 300; font-size: clamp(2.1rem, 4.1vw, 3.7rem); line-height: 1.06; letter-spacing: -.015em; color: var(--ink); margin: 0 0 clamp(24px, 3.4vw, 48px); }
.pr-hero__row { display: grid; grid-template-columns: minmax(0, 7fr) minmax(0, 5fr); gap: clamp(28px, 5vw, 80px); align-items: center; }
.primer main .pr-hero__answer { font-size: clamp(1.12rem, 1.5vw, 1.32rem); line-height: 1.6; color: var(--ink); }
.primer main .pr-hero__limit { margin-top: 18px; font-size: 18px; line-height: 1.6; color: var(--ink); border-left: 3px solid var(--accent-blue); padding-left: 18px; }
.primer main .pr-hero__for { margin-top: 18px; font-size: 16px; line-height: 1.6; color: var(--ink-muted); }
.pr-hero__art { margin: 0; }

/* the drawing: one speck from the vial, under the glass */
.pr-lens { display: block; width: 100%; max-width: 460px; height: auto; margin-inline: auto; overflow: visible; }
.pr-lens :is(path, rect, circle) { fill: none; stroke: var(--ink); stroke-width: 1.7; stroke-linecap: round; stroke-linejoin: round; }
.pr-lens .pr-lens__fluid { fill: var(--accent-wash); stroke: none; }
.pr-lens .pr-lens__specks circle { fill: var(--accent-blue); stroke: none; transform-box: fill-box; transform-origin: center; }
.pr-lens .pr-lens__zoom path { stroke: var(--border-strong); stroke-width: 1.3; stroke-dasharray: .02 .03; }
.pr-lens .pr-lens__disc { fill: #fff; stroke-width: 2.4; }
.pr-lens .pr-lens__handle { stroke-width: 9; }
.pr-lens .pr-lens__body { fill: var(--accent-wash); stroke: var(--accent-blue); stroke-width: 2; }
.pr-lens .pr-lens__nucleus { fill: var(--accent-blue); stroke: none; }
.pr-lens .pr-lens__cell { transform-box: fill-box; transform-origin: center; }
.pr-lens .pr-lens__signals circle { fill: var(--accent-ice); stroke: none; opacity: 0; }
/* with no motion the signals are shown where they are going */
.pr-lens .pr-lens__signals circle:nth-child(-n+4) { opacity: .9; transform: translate(var(--tx), var(--ty)); }

/* first paint: the vial is drawn, the glass comes over it, the cell is found, and it starts to signal */
@keyframes pr-signal { 0% { transform: translate(0, 0); opacity: 0; } 12% { opacity: .95; } 80% { opacity: .7; } 100% { transform: translate(var(--tx), var(--ty)); opacity: 0; } }
@keyframes pr-glass { from { opacity: 0; transform: translate(46px, 30px) scale(.9); } }
.pr-js .pr-hero__h1 > * { animation: pr-up 900ms var(--pr-ease) both; }
.pr-js .pr-hero__h1 > em { animation-delay: 110ms; }
.pr-js .pr-hero__text > * { animation: pr-up 900ms var(--pr-ease) 240ms both; }
.pr-js .pr-hero__text > :nth-child(2) { animation-delay: 340ms; }
.pr-js .pr-hero__text > :nth-child(3) { animation-delay: 420ms; }
.pr-js .pr-toc { animation: pr-up 900ms var(--pr-ease) 520ms both; }
.pr-js .pr-lens .d { stroke-dasharray: 1; animation: pr-draw 800ms var(--pr-ease) 200ms both; }
.pr-js .pr-lens .pr-lens__fluid { animation: pr-fade 600ms ease 800ms both; }
.pr-js .pr-lens .pr-lens__specks circle { animation: pr-pop 380ms var(--pr-ease) calc(900ms + var(--i) * 70ms) both; }
.pr-js .pr-lens .pr-lens__glass { transform-box: fill-box; transform-origin: center; animation: pr-glass 900ms var(--pr-ease) 1400ms both; }
.pr-js .pr-lens .pr-lens__zoom path { animation: pr-fade 500ms ease 2000ms both; }
.pr-js .pr-lens .pr-lens__cell { animation: pr-pop 560ms var(--pr-ease) 2100ms both; }
.pr-js .pr-lens .pr-lens__signals circle { opacity: 0; transform: none; }
/* the loops run only while their drawing is on screen (the script sets .is-live) */
.pr-js .pr-lens.is-live .pr-lens__signals circle { animation: pr-signal 4.2s ease-out calc(2700ms + var(--d)) infinite; }

/* the contents list: the page's own headings */
.pr-toc { margin-top: clamp(32px, 4.4vw, 60px); border-top: 2px solid var(--ink); }
.pr-toc__list { list-style: none; margin: 0; padding: 0; columns: 2; column-gap: clamp(32px, 5vw, 88px); }
.pr-toc__list li { break-inside: avoid; border-bottom: 1px solid var(--border); }
.pr-toc__list a { display: flex; align-items: center; justify-content: space-between; gap: 16px; min-height: 54px; padding: 8px 0; font-size: 17px; line-height: 1.35; color: var(--ink); transition: color 200ms, padding-left 360ms var(--pr-ease); }
.pr-toc__list a::after { content: ""; flex: none; width: 12px; height: 12px; margin-right: 4px; border-right: 1.7px solid var(--accent-blue); border-bottom: 1.7px solid var(--accent-blue); transform: translateY(-3px) rotate(45deg); transition: transform 360ms var(--pr-ease); }
.pr-toc__list a:hover { color: var(--accent-blue-hover); padding-left: 8px; }
.pr-toc__list a:hover::after { transform: translateY(2px) rotate(45deg); }

/* ============ CONTENTS BAR (follows the reader) ============ */
.primer .hc-bar {
  /* under the phone menu's sheet (55) and backdrop (50), over the page */
  position: fixed; left: 0; right: 0; top: var(--hc-nav-h); z-index: 49;
  height: var(--hc-bar-h);
  background: rgba(255, 255, 255, .94);
  -webkit-backdrop-filter: saturate(180%) blur(12px); backdrop-filter: saturate(180%) blur(12px);
  border-bottom: 1px solid var(--border);
  transform: translateY(-8px); opacity: 0; visibility: hidden;
  transition: opacity 260ms, transform 360ms var(--pr-ease), visibility 0s 360ms;
}
.primer .hc-bar.is-on { transform: none; opacity: 1; visibility: visible; transition: opacity 260ms, transform 360ms var(--pr-ease); }
body.primer.nav-open .hc-bar { opacity: 0; visibility: hidden; }
.primer .hc-bar__track {
  max-width: calc(1240px + 2 * var(--pr-gut)); margin: 0 auto; padding: 0 var(--pr-gut);
  height: 100%; display: flex; align-items: stretch; gap: clamp(16px, 2.2vw, 30px);
  overflow-x: auto; scrollbar-width: none; overscroll-behavior-x: contain; scroll-padding-inline: 28px;
}
.primer .hc-bar__track::-webkit-scrollbar { display: none; }
.primer .hc-bar__track a {
  position: relative; flex: none; display: flex; align-items: center;
  font-size: 14px; font-weight: 500; color: var(--ink-muted); white-space: nowrap;
  transition: color 200ms;
}
.primer .hc-bar__track a::after {
  content: ""; position: absolute; left: 0; right: 0; bottom: -1px; height: 2px;
  background: var(--accent-blue); transform: scaleX(0); transform-origin: left;
  transition: transform 360ms var(--pr-ease);
}
.primer .hc-bar__track a:hover, .primer .hc-bar__track a[aria-current] { color: var(--ink); }
.primer .hc-bar__track a:hover::after { transform: scaleX(.35); }
.primer .hc-bar__track a[aria-current]::after { transform: scaleX(1); }
.primer .hc-bar__track a:focus-visible { outline: 2px solid var(--accent-blue); outline-offset: -4px; border-radius: 4px; }
.primer .hc-bar__progress {
  position: absolute; left: 0; top: 0; height: 2px; width: 100%;
  background: var(--accent-ice); transform-origin: left; transform: scaleX(var(--hc-p, 0));
}

/* ============ THE BIOLOGY: an essay, and one tag on five different cells ============ */
.pr-bio__grid { display: grid; grid-template-columns: minmax(0, 7fr) minmax(0, 5fr); gap: clamp(32px, 5vw, 88px); align-items: start; }
.pr-bio__side { position: sticky; top: var(--pr-stick); display: grid; gap: 28px; }
.pr-kinds { margin: 0; }
.pr-kinds svg { display: block; width: 100%; height: auto; overflow: visible; }
.pr-kinds :is(path, circle, ellipse) { fill: #fff; stroke: var(--ink); stroke-width: 1.7; stroke-linecap: round; stroke-linejoin: round; }
.pr-kinds .pr-kinds__strings path { fill: none; stroke: var(--border-strong); stroke-width: 1.4; }
.pr-kinds .n { fill: rgba(11, 29, 58, .16); stroke: none; }
.pr-kinds .s { fill: var(--ink); stroke: none; }
.pr-kinds text { font-family: var(--font-body); font-size: 19px; font-weight: 500; fill: var(--ink); }
.pr-kinds .pr-kinds__tag { transform-box: view-box; transform-origin: 266px 54px; }
.pr-kinds .pr-kinds__cell > g { transform-box: fill-box; transform-origin: center; }
/* the one most clinics mean */
.pr-kinds .pr-kinds__cell--msc path { fill: var(--accent-wash); stroke: var(--accent-blue); stroke-width: 2; }
.pr-kinds .pr-kinds__cell--msc .n { fill: var(--accent-blue); }
.pr-kinds .pr-kinds__halo { fill: none; stroke: var(--accent-ice); stroke-width: 1.4; stroke-dasharray: 3 5; }
@keyframes pr-swing { 0% { transform: rotate(-16deg); opacity: 0; } 20% { opacity: 1; } 45% { transform: rotate(7deg); } 70% { transform: rotate(-3deg); } 100% { transform: none; } }
@keyframes pr-halo { from { transform: scale(.4); opacity: 0; } 60% { opacity: 1; } }
.pr-js .pr-kinds:not(.is-in) :is(.pr-kinds__tag, .pr-kinds__cell > g, .pr-kinds__strings path) { opacity: 0; }
.pr-js .pr-kinds.is-in .pr-kinds__tag { animation: pr-swing 1100ms ease-out both; }
.pr-js .pr-kinds.is-in .pr-kinds__strings path { stroke-dasharray: 1; animation: pr-draw 700ms var(--pr-ease) both; }
.pr-js .pr-kinds.is-in .pr-kinds__strings path:nth-child(1) { animation-delay: 500ms; }
.pr-js .pr-kinds.is-in .pr-kinds__strings path:nth-child(2) { animation-delay: 620ms; }
.pr-js .pr-kinds.is-in .pr-kinds__strings path:nth-child(3) { animation-delay: 740ms; }
.pr-js .pr-kinds.is-in .pr-kinds__strings path:nth-child(4) { animation-delay: 860ms; }
.pr-js .pr-kinds.is-in .pr-kinds__strings path:nth-child(5) { animation-delay: 980ms; }
.pr-js .pr-kinds.is-in .pr-kinds__cell > g { animation: pr-pop 460ms var(--pr-ease) calc(1000ms + var(--i) * 120ms) both; }
.pr-js .pr-kinds.is-in .pr-kinds__halo { transform-box: fill-box; transform-origin: center; animation: pr-halo 900ms var(--pr-ease) 2000ms both; }

/* ============ HOW THEY WORK: the drawing leads, the three things it does light in turn ============ */
.pr-how__grid { display: grid; grid-template-columns: minmax(0, 5fr) minmax(0, 7fr); gap: clamp(32px, 5vw, 88px); align-items: start; }
.pr-memo { margin: 0; position: sticky; top: var(--pr-stick); }
.pr-memo svg { display: block; width: 100%; height: auto; overflow: visible; }
.pr-memo :is(path, rect, circle) { fill: none; stroke: var(--ink); stroke-width: 1.7; stroke-linecap: round; stroke-linejoin: round; }
.pr-memo .pr-memo__lines path { stroke: var(--border-strong); stroke-width: 1.5; stroke-dasharray: 3 7; transition: stroke 400ms; }
.pr-memo .pr-memo__src path { fill: var(--accent-wash); stroke: var(--accent-blue); stroke-width: 2; }
.pr-memo .pr-memo__src .n { fill: var(--accent-blue); stroke: none; }
.pr-memo .pr-memo__env { opacity: 0; }
.pr-memo .pr-memo__env rect { fill: #fff; stroke: var(--accent-blue); }
.pr-memo .pr-memo__env path { stroke: var(--accent-blue); }
.pr-memo .pr-memo__dst rect { fill: #fff; }
/* end states, which is what is shown with no script and with reduced motion:
   the flame settled, the break attended to, the scale level */
.pr-memo .pr-memo__flame { transform-box: fill-box; transform-origin: 50% 100%; transform: scale(.6); transition: transform 900ms var(--pr-ease) 900ms; }
.pr-memo .pr-memo__flame .in { opacity: 0; transition: opacity 500ms 900ms; }
.pr-memo .crack { opacity: .28; transition: opacity 700ms 1100ms; }
.pr-memo .pr-memo__crew circle { fill: var(--accent-blue); stroke: none; transition: transform 1000ms var(--pr-ease) 700ms, opacity 400ms 700ms; }
.pr-memo .pr-memo__beam { transform-box: view-box; transform-origin: 0 -30px; transition: transform 1100ms var(--pr-ease) 900ms; }
/* before each memo lands */
.pr-memo.is-live:not(.s1) .pr-memo__flame { transform: none; }
.pr-memo.is-live:not(.s1) .pr-memo__flame .in { opacity: 1; }
.pr-memo.is-live:not(.s2) .crack { opacity: 1; }
.pr-memo.is-live:not(.s2) .pr-memo__crew circle { transform: translate(var(--dx), var(--dy)); opacity: .35; }
.pr-memo.is-live:not(.s3) .pr-memo__beam { transform: rotate(-12deg); }
.pr-memo.is-live:not(.s1, .s2, .s3) :is(.pr-memo__flame, .pr-memo__flame .in, .crack, .pr-memo__crew circle, .pr-memo__beam) { transition: none; }
.pr-memo[data-now="1"] .l1, .pr-memo[data-now="2"] .l2, .pr-memo[data-now="3"] .l3 { stroke: var(--accent-blue); }
@keyframes pr-send { 0% { offset-distance: 0%; opacity: 0; } 12% { opacity: 1; } 86% { opacity: 1; } 100% { offset-distance: 100%; opacity: 0; } }
@supports (offset-path: path("M0 0")) {
  .pr-memo .e1 { offset-path: path("M146 176C236 150 250 70 380 66"); }
  .pr-memo .e2 { offset-path: path("M152 190H380"); }
  .pr-memo .e3 { offset-path: path("M146 204C236 230 250 310 380 314"); }
  .pr-memo .pr-memo__env { offset-rotate: 0deg; }
  .pr-memo[data-now="1"] .e1, .pr-memo[data-now="2"] .e2, .pr-memo[data-now="3"] .e3 { animation: pr-send 1300ms cubic-bezier(.45, 0, .3, 1) both; }
}
/* the words the drawing is pointing at */
.pr-does { background: linear-gradient(var(--accent-wash), var(--accent-wash)) no-repeat 0 100% / 0% 100%; transition: background-size 520ms var(--pr-ease); border-radius: 2px; }
.pr-does.is-now { background-size: 100% 100%; }

/* ============ AFTER THE IV: navy, four stops on one line the reader walks ============ */
.primer main > .pr-moa { background: var(--navy-brand); color: #fff; }
.primer .pr-moa h2 { color: #fff; }
.primer .pr-moa h2 em { color: var(--accent-ice); }
.pr-moa__head { display: grid; grid-template-columns: minmax(0, 5fr) minmax(0, 7fr); gap: 16px clamp(32px, 5vw, 88px); align-items: end; margin-bottom: clamp(36px, 5vw, 72px); }
.primer .pr-moa__head h2 { margin: 0; }
.primer .pr-moa__head p { font-size: 18px; line-height: 1.65; color: rgba(255, 255, 255, .8); }
.pr-flow__wrap { position: relative; }
.pr-flow { list-style: none; margin: 0; padding: 0; display: grid; grid-template-columns: repeat(4, minmax(0, 1fr)); gap: clamp(16px, 3vw, 48px); }
.pr-step { position: relative; text-align: center; }
.pr-step__art { height: 190px; display: grid; place-items: center; margin-bottom: 44px; }
.pr-step__art svg { display: block; height: 190px; width: auto; max-width: 100%; overflow: visible; }
.pr-step__art :is(path, rect, circle, line, polygon) { fill: none; stroke: #fff; stroke-width: 1.6; stroke-linecap: round; stroke-linejoin: round; }
.pr-step__art .pr-step__fluid { fill: rgba(124, 169, 209, .38); stroke: none; }
.pr-step__art .pr-step__drip { stroke: var(--accent-ice); stroke-width: 2; stroke-dasharray: 3 9; }
.pr-step__art .pr-step__site { fill: var(--accent-ice); stroke: none; }
.pr-step__art .pr-step__tree path { stroke: rgba(255, 255, 255, .5); stroke-width: 1.2; }
.pr-step__art .pr-step__lodged circle { fill: var(--accent-ice); stroke: none; transform-box: fill-box; transform-origin: center; }
.pr-step__art .pr-step__ring { stroke: var(--accent-ice); stroke-width: 1.2; stroke-dasharray: 2 6; transform-box: fill-box; transform-origin: center; }
.pr-step__art .pr-step__body { fill: var(--navy-mid); stroke-width: 2; }
.pr-step__art .pr-step__core { fill: var(--accent-ice); stroke: none; }
.pr-step__art .pr-step__exo circle { fill: var(--accent-ice); stroke: none; transform-box: fill-box; transform-origin: center; }
.pr-step__art .pr-step__calm { stroke: var(--accent-ice); stroke-width: 1.4; }
.primer .pr-step__name { font-family: var(--font-display); font-weight: 400; font-size: clamp(1.4rem, 2vw, 1.8rem); line-height: 1.15; color: #fff; margin: 0 0 8px; }
.primer .pr-step p { font-size: 16px; line-height: 1.5; color: rgba(255, 255, 255, .78); }
/* the line, and a stop on it under each drawing */
.pr-flow__line { position: absolute; left: 12.5%; right: 12.5%; top: 211px; height: 2px; background: rgba(255, 255, 255, .2); }
.pr-flow__line i { display: block; height: 100%; background: var(--accent-ice); transform-origin: left; transform: scaleX(var(--pr-flow, 1)); }
.pr-step::before { content: ""; position: absolute; left: 50%; top: 205px; width: 14px; height: 14px; margin-left: -7px; border-radius: 50%; background: var(--accent-ice); box-shadow: 0 0 0 5px var(--navy-brand); transition: background 300ms, transform 500ms var(--pr-ease); z-index: 1; }
@keyframes pr-drip { to { stroke-dashoffset: -24; } }
@keyframes pr-ripple { 0% { transform: scale(.55); opacity: 0; } 30% { opacity: 1; } 100% { transform: scale(1.12); opacity: 0; } }
.pr-js .pr-step:not(.is-in)::before { background: #3b5486; transform: scale(.6); }
.pr-js .pr-step:not(.is-in) :is(.pr-step__art, .pr-step__name, p) { opacity: 0; }
.pr-js .pr-step :is(.pr-step__name, p) { transition: opacity 600ms ease 200ms; }
.pr-js .pr-step.is-in .pr-step__art { animation: pr-fade 300ms ease both; }
.pr-js .pr-step.is-in .pr-step__art :is(.d, .pr-step__calm) { stroke-dasharray: 1; animation: pr-draw 1000ms var(--pr-ease) both; }
.pr-js .pr-step.is-in .pr-step__calm { animation-delay: 900ms; }
.pr-js .pr-step.is-in .pr-step__fluid { animation: pr-fade 700ms ease 500ms both; }
.pr-js .pr-step.is-in .pr-step__tree path { animation: pr-fade 700ms ease 500ms both; }
.pr-js .pr-flow__wrap.is-live .pr-step.is-in .pr-step__drip { animation: pr-drip 1.6s linear infinite; }
.pr-js .pr-step.is-in .pr-step__lodged circle { animation: pr-pop 420ms var(--pr-ease) both; }
.pr-js .pr-step.is-in .pr-step__lodged circle:nth-child(1) { animation-delay: 700ms; }
.pr-js .pr-step.is-in .pr-step__lodged circle:nth-child(2) { animation-delay: 850ms; }
.pr-js .pr-step.is-in .pr-step__lodged circle:nth-child(3) { animation-delay: 1000ms; }
.pr-js .pr-step.is-in .pr-step__lodged circle:nth-child(4) { animation-delay: 1150ms; }
.pr-js .pr-step.is-in .pr-step__lodged circle:nth-child(5) { animation-delay: 1300ms; }
.pr-js .pr-step.is-in .pr-step__lodged circle:nth-child(6) { animation-delay: 1450ms; }
.pr-js .pr-flow__wrap.is-live .pr-step.is-in .pr-step__ring { animation: pr-ripple 3.2s ease-out infinite; }
.pr-js .pr-flow__wrap.is-live .pr-step.is-in .pr-step__ring--2 { animation-delay: 1.1s; }
.pr-js .pr-step.is-in .pr-step__exo circle { animation: pr-pop 500ms var(--pr-ease) both; }
.pr-js .pr-step.is-in .pr-step__exo circle:nth-child(n+4) { animation-delay: 300ms; }
.pr-js .pr-step.is-in .pr-step__exo circle:nth-child(n+7) { animation-delay: 600ms; }

.pr-moa__legend { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 0 clamp(24px, 4vw, 64px); margin-top: clamp(40px, 6vw, 80px); }
.pr-legend { border-top: 1px solid rgba(255, 255, 255, .28); padding-top: 18px; }
.pr-legend__k { display: block; font-size: 15px; color: var(--accent-ice); }
.pr-legend > strong { display: block; font-family: var(--font-display); font-weight: 400; font-size: clamp(1.7rem, 2.6vw, 2.3rem); line-height: 1.15; color: #fff; margin: 4px 0 10px; }
.primer .pr-legend p { font-size: 16px; line-height: 1.6; color: rgba(255, 255, 255, .78); }
.pr-moa .pr-more > summary { color: #c9def2; }

/* ============ THE EVIDENCE: three rows, each with the strength of its signal ============ */
.primer .pr-ev h2 { margin-bottom: 10px; }
.primer main .pr-ev__intro { margin-top: 14px; font-size: 18px; line-height: 1.7; color: var(--ink-soft); }
.pr-tiers { margin-top: clamp(28px, 4vw, 48px); border-top: 2px solid var(--ink); }
.pr-tier { display: grid; grid-template-columns: 72px minmax(0, 1fr); gap: 0 clamp(20px, 3vw, 44px); align-items: start; padding: 28px 0; border-bottom: 1px solid var(--border); }
.pr-tier__meter { display: block; width: 72px; height: 72px; }
.pr-tier__meter rect { fill: none; stroke: var(--border-strong); stroke-width: 1.5; transform-box: fill-box; transform-origin: 50% 100%; }
.pr-tier[data-level="3"] rect, .pr-tier[data-level="2"] rect:nth-child(-n+2), .pr-tier[data-level="1"] rect:nth-child(1) { fill: var(--accent-blue); stroke: var(--accent-blue); }
.pr-tier p { font-size: 17.5px; line-height: 1.7; color: var(--ink-soft); }
.pr-tier p strong { display: block; font-family: var(--font-display); font-weight: 400; font-size: clamp(1.5rem, 2.2vw, 1.9rem); line-height: 1.2; color: var(--ink); margin-bottom: 6px; }
@keyframes pr-grow { from { transform: scaleY(0); } }
.pr-js .pr-tier p { transition: opacity 620ms ease, transform 820ms var(--pr-ease); }
.pr-js .pr-tier:not(.is-in) p { opacity: 0; transform: translateX(20px); }
.pr-js .pr-tier:not(.is-in) rect { opacity: 0; }
.pr-js .pr-tier.is-in rect { animation: pr-grow 700ms var(--pr-ease) both; }
.pr-js .pr-tier.is-in rect:nth-child(2) { animation-delay: 140ms; }
.pr-js .pr-tier.is-in rect:nth-child(3) { animation-delay: 280ms; }
.pr-ev__foot { display: grid; grid-template-columns: minmax(0, 7fr) minmax(0, 5fr); gap: 28px clamp(32px, 5vw, 88px); align-items: start; margin-top: clamp(28px, 4vw, 48px); }

/* ============ THE LIMITS: five things, each struck off as it is reached ============ */
.pr-lim__grid { display: grid; grid-template-columns: minmax(0, 5fr) minmax(0, 7fr); gap: 32px clamp(32px, 5vw, 88px); align-items: start; }
.pr-lim__side { position: sticky; top: var(--pr-stick); display: grid; gap: 28px; }
.primer main .pr-lim__intro { font-size: 18px; line-height: 1.7; color: var(--ink-soft); }
.pr-cannot { list-style: none; margin: 0; padding: 0; border-top: 2px solid var(--ink); }
.pr-cant { display: grid; grid-template-columns: 56px minmax(0, 1fr); gap: 0 22px; align-items: start; padding: 24px 0; border-bottom: 1px solid var(--border); }
.pr-cant__icon { display: block; width: 56px; height: 56px; }
.pr-cant__icon svg { display: block; width: 100%; height: 100%; overflow: visible; }
.pr-cant__icon :is(path, rect, circle) { fill: none; stroke: var(--ink-muted); stroke-width: 1.6; stroke-linecap: round; stroke-linejoin: round; }
.pr-cant__icon .pr-cant__strike { stroke: var(--ink); stroke-width: 2.6; stroke-linecap: round; stroke-dasharray: 1; }
.primer .pr-cant h3, .primer .pr-flag h3 { font-family: var(--font-display); font-weight: 400; font-size: clamp(1.4rem, 2vw, 1.75rem); line-height: 1.2; color: var(--ink); }
.pr-cant .pr-fold > p { margin-top: 8px; font-size: 17px; line-height: 1.7; color: var(--ink-soft); }
.pr-js .pr-cant .pr-fold { transition: opacity 620ms ease, transform 820ms var(--pr-ease); }
.pr-js .pr-cant:not(.is-in) .pr-fold { opacity: 0; transform: translateY(14px); }
.pr-js .pr-cant:not(.is-in) .pr-cant__icon { opacity: 0; }
.pr-js .pr-cant__icon { transition: opacity 500ms ease; }
.pr-js .pr-cant:not(.is-in) .pr-cant__strike { stroke-dashoffset: 1; }
.pr-js .pr-cant .pr-cant__strike { transition: stroke-dashoffset 600ms var(--pr-ease) 520ms; }

/* ============ WHY TIJUANA: the page's one tinted band; a drive across a line, and the two rulebooks ============ */
.primer main > .pr-why { background: var(--accent-wash); }
.pr-why__grid { display: grid; grid-template-columns: minmax(0, 6fr) minmax(0, 6fr); gap: 32px clamp(32px, 5vw, 80px); align-items: start; }
.primer main .pr-why__lead { font-family: var(--font-display); font-size: clamp(1.45rem, 2.1vw, 1.9rem); line-height: 1.3; color: var(--ink); }
.pr-why__side { position: sticky; top: var(--pr-stick); display: grid; gap: 24px; }
.pr-border { margin: 0; }
.pr-border svg { display: block; width: 100%; height: auto; overflow: visible; }
.pr-border :is(path, rect, circle) { fill: none; stroke: var(--ink); stroke-width: 1.7; stroke-linecap: round; stroke-linejoin: round; }
.pr-border .pr-border__road { stroke: #fff; stroke-width: 15; }
.pr-border .pr-border__line { stroke: var(--accent-blue); stroke-width: 2; stroke-dasharray: 10 8; }
.pr-border :is(.pr-border__home, .pr-border__hosp) :is(path, rect):first-child, .pr-border .pr-border__gate rect { fill: #fff; }
.pr-border .pr-border__hosp path:nth-child(2) { stroke: var(--accent-blue); stroke-width: 4; }
.pr-border .pr-border__arm { stroke-width: 3; transform-box: view-box; transform-origin: 262px 144px; }
.pr-border .pr-border__car path { fill: var(--ink); }
.pr-border .pr-border__car circle { fill: #fff; stroke-width: 1.5; }
/* parked at the hospital door unless the script is running the drive */
.pr-border .pr-border__car { transform: translate(380px, 246px); }
@keyframes pr-lift { 0%, 34% { transform: none; } 44%, 66% { transform: rotate(72deg); } 80%, 100% { transform: none; } }
@supports (offset-path: path("M0 0")) {
  .pr-border .pr-border__car { transform: none; offset-path: path("M82 96C82 150 196 118 246 150S300 246 398 246"); offset-rotate: auto; offset-distance: 95%; }
  .pr-js .pr-border .pr-border__car { transition: offset-distance 3400ms cubic-bezier(.5, 0, .25, 1) 300ms; }
  .pr-js .pr-border:not(.is-in) .pr-border__car { offset-distance: 0%; }
  .pr-js .pr-border.is-in .pr-border__arm { animation: pr-lift 3700ms ease-in-out both; }
}

/* the two rulebooks, side by side */
.pr-compare { border-top: 2px solid var(--ink); font-size: 15px; line-height: 1.45; color: var(--ink-soft); background: #fff; border-radius: 0 0 10px 10px; }
.pr-compare__row { display: grid; grid-template-columns: minmax(0, 1.05fr) minmax(0, 1.4fr) minmax(0, 1.5fr); gap: 0 14px; padding: 12px 16px; border-bottom: 1px solid var(--border); }
.pr-compare__row:last-child { border-bottom: 0; }
.pr-compare__row--hd { font-weight: 600; color: var(--ink); }
.pr-compare__k { color: var(--ink-muted); }
.pr-compare .is-mx { color: var(--ink); font-weight: 500; }
.pr-compare__row--hd .is-mx { font-weight: 600; color: var(--accent-blue-hover); }
.pr-sr { position: absolute; width: 1px; height: 1px; overflow: hidden; clip-path: inset(50%); white-space: nowrap; }

/* ============ RED FLAGS: eight, two abreast, each with the question to ask out loud ============ */
.pr-flags__head { display: grid; grid-template-columns: minmax(0, 5fr) minmax(0, 7fr); gap: 16px clamp(32px, 5vw, 88px); align-items: end; margin-bottom: clamp(28px, 4vw, 52px); }
.primer .pr-flags__head h2 { margin: 0; }
.primer .pr-flags__head p, .primer .pr-research__head p, .primer .pr-faq__head p { font-size: 18px; line-height: 1.65; color: var(--ink-soft); }
.pr-flags__grid { display: grid; grid-template-columns: repeat(2, minmax(0, 1fr)); gap: 0 clamp(32px, 5vw, 88px); border-top: 2px solid var(--ink); }
.pr-flag { display: grid; grid-template-columns: 52px minmax(0, 1fr); gap: 0 20px; align-items: start; padding: 26px 0; border-bottom: 1px solid var(--border); }
.pr-flag__icon { display: grid; place-items: center; width: 52px; height: 52px; border: 1px solid var(--border-strong); border-radius: 50%; }
.pr-flag__icon svg { width: 26px; height: 26px; fill: none; stroke: var(--ink); stroke-width: 1.5; stroke-linecap: round; stroke-linejoin: round; }
.pr-flag .pr-fold > p { margin-top: 8px; font-size: 16.5px; line-height: 1.7; color: var(--ink-soft); }
.primer main .pr-flag .pr-flag__ask { margin-top: 14px; padding-left: 14px; border-left: 2px solid var(--accent-blue); font-size: 16.5px; line-height: 1.55; color: var(--ink); }
.pr-flag__ask span { font-weight: 600; color: var(--accent-blue-hover); margin-right: 4px; }
.pr-flag__ask q { font-style: italic; }

/* the checklist: a page you can pick up */
.pr-check { display: grid; grid-template-columns: minmax(0, 300px) minmax(0, 1fr); gap: 32px clamp(32px, 5vw, 80px); align-items: center; margin-top: clamp(48px, 7vw, 96px); }
.pr-check__doc { display: block; color: var(--ink); }
.pr-check__page { display: flex; flex-direction: column; aspect-ratio: 8.5 / 11; background: #fff; border: 1px solid var(--border-strong); border-radius: 4px; box-shadow: var(--shadow-md); padding: 26px 24px 20px; transform: rotate(-2.5deg); transition: transform 520ms var(--pr-ease), box-shadow 520ms; }
.pr-check__doc:hover .pr-check__page { transform: rotate(0deg) translateY(-6px); box-shadow: var(--shadow-lift); }
.pr-check__mark { width: 62px; height: auto; margin-bottom: auto; }
.pr-check__title { display: block; font-family: var(--font-display); font-size: 1.75rem; line-height: 1.04; margin: 18px 0 16px; }
.pr-check__title em { font-style: italic; color: var(--accent-blue); }
.pr-check__toc { list-style: none; margin: 0; padding: 0; font-size: 13px; line-height: 1.3; color: var(--ink-soft); }
.pr-check__toc li { display: flex; justify-content: space-between; gap: 12px; padding: 5px 0; border-top: 1px solid var(--border); }
.pr-check__foot { margin-top: 12px; font-size: 13px; color: var(--ink-muted); }
.primer .pr-check__h { font-family: var(--font-display); font-weight: 300; font-size: clamp(1.7rem, 2.8vw, 2.5rem); line-height: 1.12; color: var(--ink); margin: 0 0 16px; }
.pr-check__body > p { font-size: 18px; line-height: 1.7; color: var(--ink-soft); }
.pr-check__body b { font-weight: 600; color: var(--ink); }
.pr-check__meta { margin: 22px 0 26px; border-top: 1px solid var(--border); }
.pr-check__meta > div { display: grid; grid-template-columns: 130px minmax(0, 1fr); gap: 0 16px; padding: 10px 0; border-bottom: 1px solid var(--border); font-size: 16px; line-height: 1.5; }
.pr-check__meta dt { font-weight: 600; color: var(--ink); }
.pr-check__meta dd { margin: 0; color: var(--ink-soft); }
.pr-btn { display: inline-flex; align-items: center; gap: 12px; min-height: 50px; padding: 0 24px; background: var(--ink); color: #fff; font-size: 16px; font-weight: 500; border-radius: 6px; transition: background 220ms, transform 360ms var(--pr-ease), box-shadow 360ms; }
.pr-btn svg { transition: transform 360ms var(--pr-ease); }
.pr-btn:hover { background: var(--accent-blue-hover); color: #fff; transform: translateY(-2px); box-shadow: var(--shadow-lift); }
.pr-btn:hover svg { transform: translateX(5px); }
.pr-btn:active { transform: none; box-shadow: none; }
.pr-js [data-r="doc"] .pr-check__page { transition: transform 900ms var(--pr-ease), opacity 500ms ease, box-shadow 520ms; }
.pr-js [data-r="doc"]:not(.is-in) .pr-check__page { opacity: 0; transform: translateY(44px) rotate(7deg); }
.pr-js [data-r="doc"] .pr-check__body { transition: opacity 620ms ease 200ms; }
.pr-js [data-r="doc"]:not(.is-in) .pr-check__body { opacity: 0; }

/* the three companion guides */
.pr-guides { margin-top: clamp(48px, 7vw, 96px); }
.primer main .pr-guides__lead { font-family: var(--font-display); font-size: clamp(1.45rem, 2.1vw, 1.9rem); line-height: 1.3; color: var(--ink); margin-bottom: 20px; }
.pr-guides__grid { list-style: none; margin: 0; padding: 0; display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 0 clamp(24px, 4vw, 56px); }
.pr-guide { display: grid; grid-template-columns: 30px minmax(0, 1fr); gap: 4px 16px; align-content: start; height: 100%; padding: 20px 0 22px; border-top: 2px solid var(--ink); color: var(--ink); transition: border-color 260ms; }
.pr-guide__icon { grid-row: 1 / span 2; padding-top: 2px; }
.pr-guide__icon svg { display: block; width: 30px; height: 30px; fill: none; stroke: var(--ink); stroke-width: 1.4; stroke-linecap: round; stroke-linejoin: round; transition: stroke 260ms, transform 420ms var(--pr-ease); }
.pr-guide__title { font-size: 18px; font-weight: 600; line-height: 1.35; transition: color 200ms; }
.pr-arrow { display: inline-block; transition: transform 360ms var(--pr-ease); }
.pr-guide__text { font-size: 16px; line-height: 1.55; color: var(--ink-muted); }
.pr-guide:hover { border-top-color: var(--accent-blue); }
.pr-guide:hover .pr-guide__title { color: var(--accent-blue-hover); }
.pr-guide:hover .pr-arrow { transform: translateX(6px); }
.pr-guide:hover .pr-guide__icon svg { stroke: var(--accent-blue); transform: translateY(-3px); }
.pr-flags .pr-next { margin-top: 12px; }

/* ============ READING LIST: a ledger; what the paper is on the left, why it is here on the right ============ */
.pr-research__head { display: grid; grid-template-columns: minmax(0, 1fr) 140px; gap: 24px clamp(32px, 5vw, 88px); align-items: end; margin-bottom: clamp(28px, 4vw, 48px); }
.primer .pr-research__head h2 { margin-bottom: 16px; }
.pr-papers { margin: 0; }
.pr-papers svg { display: block; width: 140px; height: auto; overflow: visible; }
.pr-papers rect { fill: #fff; stroke: var(--ink); stroke-width: 1.6; }
.pr-papers .b { stroke: var(--border-strong); transform-box: fill-box; }
.pr-papers .t { fill: none; stroke: var(--border-strong); stroke-width: 2; stroke-linecap: round; }
.pr-papers .s { fill: #fff; stroke: var(--accent-blue); stroke-width: 1.8; transform-box: fill-box; transform-origin: center; }
.pr-papers .k { fill: none; stroke: var(--accent-blue); stroke-width: 2.2; stroke-linecap: round; stroke-linejoin: round; }
.pr-js .pr-papers:not(.is-in) :is(.t, .k) { stroke-dasharray: 1; stroke-dashoffset: 1; }
.pr-js .pr-papers:not(.is-in) :is(.b, .s) { opacity: 0; }
.pr-js .pr-papers.is-in .b { animation: pr-fade 500ms ease 300ms both; }
.pr-js .pr-papers.is-in .t { stroke-dasharray: 1; animation: pr-draw 520ms var(--pr-ease) both; }
.pr-js .pr-papers.is-in .t:nth-of-type(2) { animation-delay: 120ms; }
.pr-js .pr-papers.is-in .t:nth-of-type(3) { animation-delay: 240ms; }
.pr-js .pr-papers.is-in .t:nth-of-type(4) { animation-delay: 360ms; }
.pr-js .pr-papers.is-in .s { animation: pr-pop 460ms var(--pr-ease) 700ms both; }
.pr-js .pr-papers.is-in .k { stroke-dasharray: 1; animation: pr-draw 420ms var(--pr-ease) 1050ms both; }

.pr-refs { list-style: none; margin: 0; padding: 0; }
.pr-research__head + .pr-refs { border-top: 2px solid var(--ink); }
.pr-ref { display: grid; grid-template-columns: 64px minmax(0, 1fr); gap: 0 20px; padding: 26px 0; border-bottom: 1px solid var(--border); }
.pr-ref__n { font-family: var(--font-display); font-size: 2.1rem; line-height: 1; color: var(--accent-blue); font-variant-numeric: lining-nums; }
.pr-ref__body { display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1fr); gap: 6px clamp(28px, 4vw, 64px); align-items: start; }
.pr-ref__body > * { grid-column: 1; }
.pr-ref__tag { font-size: 14.5px; color: var(--ink-muted); }
.primer .pr-ref h3 { font-family: var(--font-body); font-size: 18px; font-weight: 600; line-height: 1.4; color: var(--ink); margin: 0; letter-spacing: 0; }
.pr-ref h3 a { color: inherit; text-decoration: underline; text-decoration-color: var(--border-strong); text-decoration-thickness: 1px; text-underline-offset: 4px; transition: color 200ms, text-decoration-color 200ms; }
.pr-ref h3 a::after { content: "\2197"; display: inline-block; margin-left: 6px; color: var(--accent-blue); transition: transform 320ms var(--pr-ease); }
.pr-ref h3 a:hover { color: var(--accent-blue-hover); text-decoration-color: currentColor; }
.pr-ref h3 a:hover::after { transform: translate(3px, -3px); }
.primer main .pr-ref__cite { font-size: 15px; line-height: 1.5; color: var(--ink-muted); }
.pr-ref__cite em { font-style: italic; }
.primer main .pr-ref__note { grid-column: 2; grid-row: 1 / span 3; font-size: 16.5px; line-height: 1.65; color: var(--ink-soft); }
/* a paper or a term the reader was just sent to */
@keyframes pr-flash { 0%, 55% { background-color: var(--accent-wash); box-shadow: -14px 0 0 var(--accent-wash), 14px 0 0 var(--accent-wash); } 100% { background-color: transparent; box-shadow: -14px 0 0 transparent, 14px 0 0 transparent; } }
:is(.pr-ref, .pr-gloss__item).is-flash { animation: pr-flash 2200ms ease-out both; }
/* and the way back to where they were reading */
.pr-back { grid-column: 1 / -1; justify-self: start; display: inline-flex; align-items: center; gap: 8px; min-height: 44px; margin-top: 6px; padding: 0; background: none; border: 0; font: 600 15px/1.2 var(--font-body); color: var(--accent-blue-hover); cursor: pointer; text-decoration: underline; text-decoration-color: transparent; text-underline-offset: 4px; transition: color 200ms, text-decoration-color 260ms; animation: pr-up 500ms var(--pr-ease) both; }
.pr-back span { display: inline-block; transition: transform 360ms var(--pr-ease); }
.pr-back:hover { color: var(--accent-blue); text-decoration-color: currentColor; }
.pr-back:hover span { transform: translateY(-4px); }

/* ============ QUESTIONS: the group named on the left, its answers opening on the right ============ */
.pr-faq__head { margin-bottom: clamp(28px, 4vw, 48px); }
.primer .pr-faq__head h2 { margin-bottom: 16px; }
.pr-faq__group { display: grid; grid-template-columns: minmax(0, 3fr) minmax(0, 9fr); gap: 8px clamp(32px, 5vw, 88px); align-items: start; padding: 24px 0 8px; border-top: 2px solid var(--ink); }
.pr-faq__group + .pr-faq__group { margin-top: 28px; }
.primer .pr-faq__label { position: sticky; top: var(--pr-stick); font-family: var(--font-display); font-weight: 400; font-size: clamp(1.5rem, 2.2vw, 1.9rem); line-height: 1.2; color: var(--ink); margin: 0; }
.pr-faq__list details { border-bottom: 1px solid var(--border); }
.pr-faq__list details:last-child { border-bottom: 0; }
.pr-faq__list summary { display: flex; align-items: center; justify-content: space-between; gap: 16px; min-height: 60px; padding: 10px 0; cursor: pointer; font-size: 18px; font-weight: 500; line-height: 1.4; color: var(--ink); transition: color 200ms; -webkit-tap-highlight-color: transparent; }
.pr-faq__list summary:hover { color: var(--accent-blue-hover); }
.pr-faq__list .pr-chev { display: block; }
.pr-faq__list summary:hover .pr-chev { transform: translateY(3px); }
.pr-faq__list details[open] > summary:hover .pr-chev { transform: rotate(180deg) translateY(3px); }
.pr-faq__a { padding: 0 44px 22px 0; }
.pr-faq__a p { font-size: 17px; line-height: 1.7; color: var(--ink-soft); }
.pr-faq__a strong { font-weight: 600; color: var(--ink); }
.pr-js .pr-faq__list details[open] > .pr-faq__a { animation: pr-unfold 360ms var(--pr-ease) both; }
.pr-js .pr-faq__group[data-r] { transition-delay: 0ms; }

/* ============ GLOSSARY: the word, then what it means ============ */
.pr-gloss__head { display: flex; align-items: end; justify-content: space-between; gap: 24px; margin-bottom: clamp(24px, 3.4vw, 44px); }
.primer .pr-gloss__head h2 { margin: 0; }
.pr-book { margin: 0; flex: none; }
.pr-book svg { display: block; width: 132px; height: auto; overflow: visible; }
.pr-book path { fill: none; stroke: var(--ink); stroke-width: 1.6; stroke-linecap: round; stroke-linejoin: round; }
.pr-book .t { stroke: var(--accent-blue); stroke-width: 1.8; }
.pr-js .pr-book:not(.is-in) path { stroke-dasharray: 1; stroke-dashoffset: 1; }
.pr-js .pr-book.is-in path { stroke-dasharray: 1; animation: pr-draw 900ms var(--pr-ease) both; }
.pr-js .pr-book.is-in .t { animation-duration: 500ms; animation-delay: 700ms; }
.pr-js .pr-book.is-in .t:nth-of-type(4) { animation-delay: 800ms; }
.pr-js .pr-book.is-in .t:nth-of-type(5) { animation-delay: 900ms; }
.pr-js .pr-book.is-in .t:nth-of-type(6) { animation-delay: 1000ms; }
.pr-js .pr-book.is-in .t:nth-of-type(7) { animation-delay: 1100ms; }
.pr-gloss__list { margin: 0; }
.pr-gloss__head + .pr-gloss__list { border-top: 2px solid var(--ink); }
.pr-gloss__item { display: grid; grid-template-columns: minmax(0, 4fr) minmax(0, 8fr); gap: 4px clamp(32px, 5vw, 88px); align-items: baseline; padding: 20px 0; border-bottom: 1px solid var(--border); }
.pr-gloss__item dt { font-family: var(--font-display); font-size: clamp(1.5rem, 2.2vw, 1.9rem); line-height: 1.15; color: var(--ink); }
.pr-gloss__item dt span { display: block; font-family: var(--font-body); font-size: 15px; line-height: 1.4; color: var(--ink-muted); margin-top: 4px; }
.pr-gloss__item dd { margin: 0; font-size: 17px; line-height: 1.7; color: var(--ink-soft); }

/* a term's meaning, shown where the reader is */
.pr-tip { position: absolute; z-index: 45; left: 0; top: 0; width: max-content; max-width: min(360px, calc(100vw - 32px)); padding: 14px 16px 15px; background: var(--ink); color: #fff; border-radius: 8px; box-shadow: var(--shadow-lift); font: 400 15px/1.55 var(--font-body); opacity: 0; transform: translateY(6px); transition: opacity 180ms ease, transform 260ms var(--pr-ease), visibility 0s 260ms; visibility: hidden; }
.pr-tip.is-on { opacity: 1; transform: none; visibility: visible; transition: opacity 180ms ease, transform 260ms var(--pr-ease); }
.pr-tip b { display: block; font-weight: 600; margin-bottom: 4px; }
/* the colon is for a screen reader; on screen the term already has its own line */
.pr-tip__sep { position: absolute; width: 1px; height: 1px; overflow: hidden; clip-path: inset(50%); }
/* the gap between a term and its tip is the tip's too, so the pointer can cross it */
.pr-tip::before { content: ""; position: absolute; inset: -10px 0; z-index: -1; }

/* ============ CLOSING CALL: narrow and centred on purpose ============ */
.primer main > .pr-cta { background: var(--navy-brand); color: #fff; text-align: center; }
.pr-cta__inner { max-width: calc(820px + 2 * var(--pr-gut)); }
.primer .pr-cta h2 { color: #fff; margin-bottom: 20px; }
.primer .pr-cta h2 em { color: var(--accent-ice); }
.primer .pr-cta p { font-size: 18px; line-height: 1.65; color: rgba(255, 255, 255, .82); }
.pr-cta__actions { display: flex; flex-direction: column; align-items: center; gap: 14px; margin-top: 30px; }
.primer .pr-cta__btn { background: #fff; color: var(--ink); border-color: #fff; min-height: 52px; transition: background 220ms, color 220ms, transform 360ms var(--pr-ease), box-shadow 360ms; }
.primer .pr-cta__btn:hover { background: var(--accent-ice); border-color: var(--accent-ice); color: var(--ink); transform: translateY(-3px); box-shadow: var(--shadow-inverted); }
.primer .pr-cta__btn:active { transform: none; }
.pr-cta__small { font-size: 15px; color: rgba(255, 255, 255, .74); }
.primer .pr-cta .pr-cta__up { margin-top: 26px; }
.pr-cta .pr-go { color: #c9def2; }
.pr-cta .pr-go:hover { color: #fff; }

/* ============ NARROWER SCREENS ============ */
@media (max-width: 1100px) {
  .primer .hc-bar__track { -webkit-mask-image: linear-gradient(90deg, transparent 0, #000 16px, #000 calc(100% - 28px), transparent); mask-image: linear-gradient(90deg, transparent 0, #000 16px, #000 calc(100% - 28px), transparent); }
}
@media (max-width: 960px) {
  .pr-hero__row, .pr-bio__grid, .pr-how__grid, .pr-lim__grid, .pr-why__grid, .pr-ev__foot, .pr-moa__head, .pr-flags__head { grid-template-columns: minmax(0, 1fr); }
  .pr-bio__side, .pr-memo, .pr-lim__side, .pr-why__side, .primer .pr-faq__label { position: static; }
  .pr-hero__art { order: -1; }
  .pr-lens { max-width: 300px; }
  .pr-kinds, .pr-memo { max-width: 520px; }
  .pr-flags__grid { grid-template-columns: minmax(0, 1fr); }
  .pr-guides__grid { grid-template-columns: minmax(0, 1fr); }
  .pr-ref__body { grid-template-columns: minmax(0, 1fr); }
  .primer main .pr-ref__note { grid-column: 1; grid-row: auto; margin-top: 6px; }
  .pr-faq__group { grid-template-columns: minmax(0, 1fr); }
  .pr-moa__legend { grid-template-columns: minmax(0, 1fr); gap: 24px; }
}
@media (max-width: 760px) {
  html:has(body.primer) { --hc-bar-h: 48px; }
  .primer .hc-bar__track { gap: 22px; }
  .pr-toc__list { columns: 1; }
  .pr-prose > p, .pr-more > p, .primer main .pr-limit, .primer main .pr-ev__intro, .primer main .pr-lim__intro { font-size: 17px; }
  /* the folds become controls */
  .pr-more > summary { display: inline-flex; align-items: center; gap: 6px; min-height: 44px; cursor: pointer; font-size: 16px; font-weight: 600; color: var(--accent-blue-hover); -webkit-tap-highlight-color: transparent; }
  .pr-more > summary .pr-chev, .pr-fold > summary .pr-chev { display: block; color: currentColor; }
  .pr-fold > summary .pr-chev { color: var(--accent-blue-hover); }
  .primer main .pr-more[open] > summary + * { margin-top: 6px; }
  .pr-fold > summary { cursor: pointer; min-height: 56px; -webkit-tap-highlight-color: transparent; }
  .pr-more--list > summary, .pr-more--legend > summary { margin-top: 6px; }
  .pr-more--legend:not([open]) { margin-top: 12px; }
  .pr-js details:is(.pr-more, .pr-fold)[open] > :not(summary) { animation: pr-unfold 360ms var(--pr-ease) both; }
  /* the four stops run down the page, the line beside them */
  .pr-flow { grid-template-columns: minmax(0, 1fr); gap: 0; }
  .pr-step { display: grid; grid-template-columns: 96px minmax(0, 1fr); gap: 0 20px; align-items: center; text-align: left; padding: 18px 0 18px 30px; }
  .pr-step__art { grid-row: 1 / span 2; height: 110px; margin: 0; }
  .pr-step__art svg { height: 110px; }
  .primer .pr-step__name { align-self: end; }
  .primer .pr-step p { align-self: start; }
  .pr-flow__line { left: 6px; right: auto; top: 28px; bottom: 28px; width: 2px; height: auto; }
  .pr-flow__line i { width: 100%; transform-origin: top; transform: scaleY(var(--pr-flow, 1)); }
  .pr-step::before { left: 7px; top: 50%; margin-top: -7px; }
  .pr-tier { grid-template-columns: 52px minmax(0, 1fr); }
  .pr-tier__meter { width: 52px; height: 52px; }
  .pr-cant { grid-template-columns: 48px minmax(0, 1fr); gap: 0 16px; padding: 12px 0; }
  .pr-cant__icon { width: 48px; height: 48px; margin-top: 4px; }
  .pr-cant .pr-fold > p, .pr-flag .pr-fold > p { margin-top: 2px; }
  .pr-cant .pr-fold[open], .pr-flag .pr-fold[open] { padding-bottom: 12px; }
  .pr-flag { grid-template-columns: 48px minmax(0, 1fr); gap: 0 16px; padding: 12px 0; }
  .pr-flag__icon { width: 48px; height: 48px; margin-top: 4px; }
  .pr-check { grid-template-columns: minmax(0, 1fr); }
  .pr-check__doc { max-width: 250px; margin-inline: auto; }
  .pr-check__meta > div { grid-template-columns: minmax(0, 1fr); }
  .pr-ref { grid-template-columns: 44px minmax(0, 1fr); gap: 0 12px; padding: 22px 0; }
  .pr-ref__n { font-size: 1.7rem; }
  .pr-research__head { grid-template-columns: minmax(0, 1fr); }
  .pr-papers { order: -1; }
  .pr-papers svg { width: 96px; }
  .pr-book svg { width: 92px; }
  .pr-gloss__item { grid-template-columns: minmax(0, 1fr); }
  .pr-faq__a { padding-right: 0; }
  .pr-next { display: block; }
  .pr-next ul { display: block; }
  /* the two rulebooks stack: each row names itself, each cell names its column */
  .pr-compare__row--hd { display: none; }
  .pr-compare__row { grid-template-columns: minmax(0, 1fr); gap: 6px; padding: 14px 16px; }
  .pr-compare__k { font-weight: 600; color: var(--ink); font-size: 16px; }
  .pr-compare__row [data-col]::before { content: attr(data-col); display: block; font-size: 14px; font-weight: 400; color: var(--ink-muted); }
}

/* ============ NO MOTION, AND PAPER ============ */
@media (prefers-reduced-motion: reduce) {
  .primer main *, .primer main *::before, .primer main *::after, .primer .hc-bar, .pr-tip { animation: none !important; transition: none !important; }
}
@media print {
  .primer .hc-bar, .pr-tip, .pr-back { display: none !important; }
  .primer main [data-r], .primer main [data-r] *, .pr-step, .pr-step *, .pr-step::before { opacity: 1 !important; transform: none !important; transition: none !important; animation: none !important; }
  .pr-lens__signals, .pr-memo__env { display: none; }
  .pr-more > summary { display: none !important; }
  .primer main > section { break-inside: auto; padding-block: 24px; }
  .primer main > .pr-moa, .primer main > .pr-cta { background: #fff; color: var(--ink); }
  .primer .pr-moa :is(h2, .pr-step__name, .pr-legend > strong), .primer .pr-cta h2 { color: var(--ink); }
  .primer .pr-moa p, .primer .pr-cta p { color: var(--ink-soft); }
  .pr-step__art :is(path, rect, circle, line, polygon) { stroke: var(--ink); }
  .pr-bio__side, .pr-memo, .pr-lim__side, .pr-why__side, .primer .pr-faq__label { position: static; }
  .pr-ref, .pr-flag, .pr-cant, .pr-gloss__item, .pr-tier { break-inside: avoid; }
}

/* Paper is taken the instant the print dialog opens: nothing may still be fading or sliding in. */
@media print {
  main *, main *::before, main *::after { animation: none !important; transition: none !important; }
}