/* ==========================================================================
   Gekko Photonics — scroll narrative site (concept build)
   Built on the "Spectra" design system: tokens/ + fonts.css are the canon.
   Nothing below invents a brand value; the only added scale is the spectral
   ramp, which is measurement data visualisation, not brand colour.
   ========================================================================== */

:root{
  /* Spectral ramp — visualisation of dispersed light. Not a brand palette. */
  --sx-1:#4b2ea8; --sx-2:#2b53d6; --sx-3:#009fe3; --sx-4:#22b47a;
  --sx-5:#cfd23a; --sx-6:#e8a33a; --sx-7:#e34b3c;
  --laser-785:#e34b3c;      /* excitation line, drawn in its nominal colour */
  --nav-h:64px;
}

/* ---------- base ---------- */
*,*::before,*::after{box-sizing:border-box}
html{-webkit-text-size-adjust:100%;scroll-behavior:smooth}
body{
  margin:0;background:var(--navy-900);color:var(--text-on-dark);
  font-family:var(--font-body);font-size:var(--fs-body);line-height:var(--lh-relaxed);
  font-weight:var(--fw-regular);-webkit-font-smoothing:antialiased;
  overflow-x:hidden;
}
h1,h2,h3,h4{font-family:var(--font-display);font-weight:var(--fw-semibold);
  letter-spacing:var(--ls-display);line-height:var(--lh-snug);margin:0 0 var(--sp-4)}
h1{font-size:var(--fs-display);line-height:var(--lh-tight)}
h2{font-size:clamp(1.75rem,3.4vw,2.75rem)}
h3{font-size:var(--fs-h3)}
h4{font-size:var(--fs-h4);font-weight:var(--fw-semibold)}
p{margin:0 0 var(--sp-4);max-width:68ch}
a{color:var(--text-link);text-decoration:none;text-underline-offset:3px}
a:hover{text-decoration:underline}
img,svg{max-width:100%;height:auto;display:block}
ul,ol{margin:0;padding:0;list-style:none}
strong{font-weight:var(--fw-semibold);color:var(--text-strong)}
.num{font-variant-numeric:tabular-nums lining-nums;font-family:var(--font-display)}
.lead{font-size:var(--fs-lead);color:var(--text-on-dark-muted);line-height:var(--lh-relaxed)}
.muted{color:var(--text-on-dark-muted)}
.unit{font-size:.58em;font-weight:var(--fw-medium);letter-spacing:0;
  color:var(--text-on-dark-muted);font-family:var(--font-body)}

/* ---------- browser surfaces (theme what we did not draw) ---------- */
::selection{background:var(--azure-500);color:#04121c}
:focus-visible{outline:2px solid var(--azure-400);outline-offset:3px;border-radius:var(--r-xs)}
html{scrollbar-color:var(--navy-600) var(--navy-950);scrollbar-width:thin;caret-color:var(--azure-400)}
::-webkit-scrollbar{width:11px;height:11px}
::-webkit-scrollbar-track{background:var(--navy-950)}
::-webkit-scrollbar-thumb{background:var(--navy-600);border:3px solid var(--navy-950);border-radius:var(--r-pill)}
::-webkit-scrollbar-thumb:hover{background:var(--indigo-500)}

/* ---------- layout ---------- */
.wrap{width:100%;max-width:var(--container);margin-inline:auto;padding-inline:var(--sp-6)}
.wrap-wide{max-width:var(--container-wide)}
.section{padding-block:clamp(var(--sp-20),9vw,var(--sp-32))}
.section--light{background:var(--paper);color:var(--text-body)}
.section--light h1,.section--light h2,.section--light h3,.section--light h4{color:var(--text-strong)}
.section--light .lead,.section--light .muted{color:var(--text-muted)}
.section--light strong{color:var(--text-strong)}
.section--raised{background:var(--navy-800)}
.section--deep{background:var(--navy-950)}
.hairline{height:1px;background:var(--border-on-dark);border:0;margin:0}
.section--light .hairline{background:var(--border-hairline)}

/* section heading block — asymmetric, never centred */
.head{display:grid;grid-template-columns:minmax(0,7fr) minmax(0,5fr);
  gap:var(--sp-10) var(--sp-16);align-items:end;margin-bottom:var(--sp-16)}
.head p{margin:0}
.head--solo{grid-template-columns:minmax(0,8fr);max-width:52rem}

/* ---------- nav ---------- */
.progress{position:fixed;top:0;left:0;height:2px;background:var(--azure-500);
  width:var(--scroll,0%);z-index:60;transition:width 80ms linear}
.nav{position:fixed;top:0;left:0;right:0;height:var(--nav-h);z-index:50;
  background:rgba(246,248,251,.94);border-bottom:1px solid var(--border-on-dark)}
.nav-in{height:100%;display:flex;align-items:center;gap:var(--sp-8)}
.brand{display:flex;align-items:center;gap:var(--sp-3);flex:0 0 auto}
.brand img{height:30px;width:auto}
.brand:hover{text-decoration:none}
.nav-links{display:flex;gap:var(--sp-1);margin-left:auto;align-items:center}
.nav-links a{color:var(--text-on-dark-muted);font-size:var(--fs-sm);font-weight:var(--fw-medium);
  padding:var(--sp-2) var(--sp-3);border-radius:var(--r-sm);transition:color var(--dur-fast) var(--ease-standard),background var(--dur-fast) var(--ease-standard)}
.nav-links a:hover{color:var(--text-strong);background:rgba(14,19,36,.05);text-decoration:none}
.nav-links a[aria-current="page"]{color:var(--text-strong);box-shadow:inset 0 -2px 0 var(--azure-500)}
.nav-toggle{display:none}

/* ---------- buttons ---------- */
.btn{display:inline-flex;align-items:center;gap:var(--sp-2);font-family:var(--font-body);
  font-size:var(--fs-sm);font-weight:var(--fw-semibold);letter-spacing:0;
  padding:var(--sp-3) var(--sp-5);border-radius:var(--r-sm);border:1px solid transparent;
  cursor:pointer;transition:background var(--dur-fast) var(--ease-standard),
  border-color var(--dur-fast) var(--ease-standard),transform var(--dur-fast) var(--ease-standard)}
.btn:hover{text-decoration:none}
.btn:active{transform:translateY(1px)}
.btn--primary{background:var(--indigo-600);color:var(--white)}
.btn--primary:hover{background:var(--indigo-500)}
.btn--ghost{background:transparent;color:var(--text-on-dark);border-color:rgba(14,19,36,.22)}
.btn--ghost:hover{border-color:var(--azure-500);color:var(--indigo-600)}
.btn--light{background:var(--white);color:var(--indigo-700);border-color:var(--steel-200)}
.btn--light:hover{background:var(--mist)}
.btn--lg{font-size:var(--fs-body);padding:var(--sp-4) var(--sp-6)}
.btn svg{width:16px;height:16px;flex:0 0 auto}

/* ---------- hero ---------- */
.hero{position:relative;padding-top:calc(var(--nav-h) + clamp(var(--sp-16),9vw,var(--sp-32)));
  padding-bottom:clamp(var(--sp-16),8vw,var(--sp-24));overflow:hidden;
  /* the one permitted gradient, hero only */
  background:
    radial-gradient(120% 90% at 88% 12%,rgba(43,44,130,.10) 0%,rgba(43,44,130,0) 62%),
    linear-gradient(178deg,var(--paper) 0%,var(--paper) 55%,var(--mist) 100%);
}
.hero-grid{display:grid;grid-template-columns:minmax(0,7fr) minmax(0,4fr);
  gap:var(--sp-12) var(--sp-16);align-items:end}
.hero h1{max-width:22ch;margin-bottom:var(--sp-6)}
.hero .lead{max-width:46ch}
.hero-meta{display:flex;flex-direction:column;gap:var(--sp-5);
  border-left:1px solid var(--border-on-dark);padding-left:var(--sp-6)}
.hero-meta div{display:flex;flex-direction:column;gap:2px}
.hero-meta dt,.hero-meta .k{font-size:var(--fs-xs);color:var(--text-on-dark-muted);
  text-transform:uppercase;letter-spacing:var(--ls-label)}
.hero-meta .v{font-family:var(--font-display);font-size:1.125rem;font-weight:var(--fw-medium);
  font-variant-numeric:tabular-nums}
.hero-cta{display:flex;flex-wrap:wrap;gap:var(--sp-3);margin-top:var(--sp-8)}
.scroll-hint{display:flex;align-items:center;gap:var(--sp-3);margin-top:var(--sp-16);
  font-size:var(--fs-xs);color:var(--text-faint);letter-spacing:var(--ls-label);text-transform:uppercase}
.scroll-hint span::after{content:"";display:block;width:56px;height:1px;background:var(--steel-500)}

/* ==========================================================================
   Scroll stage — the pinned, scroll-driven narrative
   ========================================================================== */
.stage{position:relative;background:var(--navy-950);
  border-block:1px solid var(--border-on-dark)}
.stage-pin{position:sticky;top:0;height:100vh;display:flex;flex-direction:column;
  justify-content:center;overflow:hidden}
.stage-inner{display:grid;grid-template-columns:minmax(0,1fr);
  gap:var(--sp-8);align-items:center;width:100%;max-width:var(--container-wide);
  margin-inline:auto;padding-inline:var(--sp-6)}
.stage-vis{position:relative;max-width:min(92vw,60rem);margin-inline:auto;width:100%}
.stage-vis svg{width:100%;height:auto}
.stage--wide .stage-vis{max-width:min(94vw,var(--container-wide))}
.stage-copy{position:relative;min-height:14rem;max-width:52rem;margin-inline:auto;width:100%}
.step{position:absolute;inset:0;opacity:0;transform:translateY(14px);
  transition:opacity 320ms var(--ease-out),transform 320ms var(--ease-out);
  pointer-events:none}
.step.is-active{opacity:1;transform:none;pointer-events:auto}
.step-no{font-family:var(--font-display);font-size:var(--fs-sm);font-weight:var(--fw-semibold);
  font-variant-numeric:tabular-nums;color:var(--azure-700);display:block;margin-bottom:var(--sp-3)}
.step h3{font-size:var(--fs-h2);margin-bottom:var(--sp-3)}
.step p{font-size:var(--fs-lead);color:var(--text-on-dark-muted);max-width:56ch}
.step .figs{display:flex;flex-wrap:wrap;gap:var(--sp-2) var(--sp-4);margin-top:var(--sp-5);
  padding-top:var(--sp-4);border-top:1px solid var(--border-on-dark)}
.step .figs b{font-family:var(--font-display);font-variant-numeric:tabular-nums;
  font-weight:var(--fw-semibold);font-size:1.0625rem;display:block}
.step .figs small{font-size:var(--fs-xs);color:var(--text-faint);letter-spacing:.02em}
.step blockquote{margin:var(--sp-5) 0 0;padding-left:var(--sp-4);
  border-left:1px solid var(--azure-600);font-size:var(--fs-sm);color:var(--text-on-dark)}
.step blockquote cite{display:block;margin-top:var(--sp-2);font-style:normal;
  font-size:var(--fs-xs);color:var(--text-faint)}

/* rail: step ticks + skip */
.stage-rail{position:absolute;left:0;right:0;bottom:0;padding:var(--sp-4) var(--sp-6);
  display:flex;align-items:center;gap:var(--sp-4);
  border-top:1px solid var(--border-on-dark);background:linear-gradient(to top,rgba(246,248,251,.92),rgba(246,248,251,0))}
.rail-label{font-size:var(--fs-xs);letter-spacing:var(--ls-label);text-transform:uppercase;
  color:var(--text-faint);white-space:nowrap}
.rail-ticks{display:flex;gap:6px;flex:1 1 auto;align-items:center}
.rail-ticks i{display:block;height:3px;flex:1 1 0;background:var(--navy-600);border-radius:var(--r-pill);
  transition:background var(--dur-base) var(--ease-standard)}
.rail-ticks i.on{background:var(--azure-500)}
.rail-skip{font-size:var(--fs-xs);color:var(--text-on-dark-muted);letter-spacing:var(--ls-label);
  text-transform:uppercase;background:none;border:0;cursor:pointer;padding:var(--sp-2)}
.rail-skip:hover{color:var(--text-strong)}
.stage-note{position:absolute;top:calc(var(--nav-h) + var(--sp-4));right:var(--sp-6);
  max-width:20rem;font-size:var(--fs-xs);color:var(--text-faint);text-align:right;line-height:1.5}

/* fallback when JS is off or motion is reduced: everything visible, in flow */
.stage.is-static .stage-pin{position:relative;height:auto;padding-block:var(--sp-16)}
.stage.is-static .stage-inner{grid-template-columns:minmax(0,1fr);gap:var(--sp-12)}
.stage.is-static .stage-copy{position:static;min-height:0;display:grid;
  grid-template-columns:repeat(auto-fit,minmax(15rem,1fr));gap:var(--sp-8)}
.stage.is-static .step{position:static;opacity:1;transform:none;pointer-events:auto}
.stage.is-static .stage-rail,.stage.is-static .stage-note{display:none}

/* ---------- cards / grids ---------- */
.grid{display:grid;gap:var(--sp-6)}
.grid--2{grid-template-columns:repeat(auto-fit,minmax(19rem,1fr))}
.grid--3{grid-template-columns:repeat(auto-fit,minmax(15rem,1fr))}
.card{background:var(--navy-800);border:1px solid var(--border-on-dark);border-radius:var(--r-md);
  padding:var(--sp-6)}
.card h4{margin-bottom:var(--sp-2)}
.card p{font-size:var(--fs-sm);color:var(--text-on-dark-muted);margin:0}
.card--light{background:var(--white);border-color:var(--border-hairline);box-shadow:var(--shadow-sm)}
.card--light p{color:var(--text-body)}
.card--panel{border-radius:var(--r-lg);padding:var(--sp-8)}
.card--wide{grid-column:span 2}
.card-ico{width:24px;height:24px;color:var(--indigo-600);margin-bottom:var(--sp-4)}
.section--light .card-ico{color:var(--indigo-600)}

/* dense definition list, the technical-grid signature */
.dl{display:grid;grid-template-columns:minmax(9rem,auto) 1fr;gap:0;
  border-top:1px solid var(--border-on-dark);font-size:var(--fs-sm)}
.dl dt,.dl dd{margin:0;padding:var(--sp-3) var(--sp-4) var(--sp-3) 0;
  border-bottom:1px solid var(--border-on-dark)}
.dl dt{color:var(--text-on-dark-muted)}
.dl dd{font-variant-numeric:tabular-nums;text-align:right;padding-right:0}
.section--light .dl,.section--light .dl dt,.section--light .dl dd{border-color:var(--border-hairline)}
.section--light .dl dt{color:var(--text-muted)}

/* spec table */
.table-scroll{overflow-x:auto;border:1px solid var(--border-hairline);border-radius:var(--r-md);background:var(--white)}
table{border-collapse:collapse;width:100%;font-size:var(--fs-sm);min-width:44rem}
th,td{text-align:left;padding:var(--sp-3) var(--sp-4);border-bottom:1px solid var(--border-hairline);
  vertical-align:top;color:var(--text-body)}
thead th{font-family:var(--font-display);font-size:var(--fs-xs);text-transform:uppercase;
  letter-spacing:var(--ls-label);color:var(--text-muted);background:var(--mist);
  position:sticky;top:0;white-space:nowrap}
tbody th{font-weight:var(--fw-medium);color:var(--text-strong);white-space:nowrap}
td{font-variant-numeric:tabular-nums}
tbody tr:last-child td,tbody tr:last-child th{border-bottom:0}
caption{caption-side:bottom;text-align:left;padding:var(--sp-3) var(--sp-4);
  font-size:var(--fs-xs);color:var(--text-muted)}

/* tags */
.tags{display:flex;flex-wrap:wrap;gap:var(--sp-2)}
.tag{font-size:var(--fs-xs);font-weight:var(--fw-medium);padding:3px var(--sp-2);
  border-radius:var(--r-sm);border:1px solid var(--border-on-dark);color:var(--text-on-dark-muted);
  font-variant-numeric:tabular-nums}
.section--light .tag{border-color:var(--border-hairline);color:var(--text-muted);background:var(--white)}
.tag--ok{color:var(--ok-500);border-color:rgba(63,157,84,.45)}

/* one gold moment per page */
.focal{border:1px solid rgba(217,164,65,.4);border-radius:var(--r-lg);padding:var(--sp-8);
  background:linear-gradient(180deg,rgba(217,164,65,.06),rgba(217,164,65,0))}
.focal .big{font-family:var(--font-display);font-size:var(--fs-data-xl);line-height:1;
  font-weight:var(--fw-semibold);color:var(--gold-500);font-variant-numeric:tabular-nums;
  letter-spacing:var(--ls-display)}
.focal p{margin:var(--sp-4) 0 0;font-size:var(--fs-sm)}
.section--light .focal{background:linear-gradient(180deg,rgba(217,164,65,.1),rgba(217,164,65,0));
  border-color:rgba(217,164,65,.5)}
.section--light .focal .big{color:var(--gold-700)}

/* FAQ */
.faq{border-top:1px solid var(--border-hairline)}
.faq details{border-bottom:1px solid var(--border-hairline)}
.faq summary{cursor:pointer;list-style:none;padding:var(--sp-5) var(--sp-8) var(--sp-5) 0;
  font-family:var(--font-display);font-size:1.125rem;font-weight:var(--fw-medium);
  color:var(--text-strong);position:relative}
.faq summary::-webkit-details-marker{display:none}
.faq summary::after{content:"";position:absolute;right:var(--sp-2);top:50%;width:11px;height:11px;
  border-right:1.5px solid var(--steel-400);border-bottom:1.5px solid var(--steel-400);
  transform:translateY(-70%) rotate(45deg);transition:transform var(--dur-base) var(--ease-standard)}
.faq details[open] summary::after{transform:translateY(-30%) rotate(225deg)}
.faq details[open] summary{color:var(--indigo-600)}
.faq .a{padding:0 var(--sp-16) var(--sp-6) 0;color:var(--text-body);font-size:var(--fs-sm)}
.faq .a p{max-width:70ch}

/* quote block */
.pull{font-family:var(--font-display);font-size:clamp(1.25rem,2.3vw,1.75rem);
  font-weight:var(--fw-light);line-height:1.35;letter-spacing:var(--ls-tight);max-width:34ch;margin:0}
.pull cite{display:block;margin-top:var(--sp-5);font-family:var(--font-body);font-style:normal;
  font-size:var(--fs-sm);color:var(--text-on-dark-muted);font-weight:var(--fw-regular)}
.section--light .pull cite{color:var(--text-muted)}

/* CTA band */
.cta{background:var(--indigo-100);border-top:1px solid var(--border-hairline)}
.cta-in{display:grid;grid-template-columns:minmax(0,1.4fr) minmax(0,1fr);gap:var(--sp-10);
  align-items:center;padding-block:clamp(var(--sp-16),7vw,var(--sp-24))}
.cta h2{margin-bottom:var(--sp-3)}
.cta p{color:var(--text-body);margin:0}

/* footer */
.foot{background:var(--navy-950);padding-block:var(--sp-16) var(--sp-10);font-size:var(--fs-sm)}
.foot-grid{display:grid;grid-template-columns:minmax(0,1.4fr) repeat(3,minmax(0,1fr));gap:var(--sp-10)}
.foot h5{font-family:var(--font-display);font-size:var(--fs-xs);text-transform:uppercase;
  letter-spacing:var(--ls-label);color:var(--text-faint);margin:0 0 var(--sp-4);font-weight:var(--fw-semibold)}
.foot a{color:var(--text-on-dark-muted)}
.foot a:hover{color:var(--text-strong)}
.foot li{margin-bottom:var(--sp-2)}
.foot address{font-style:normal;color:var(--text-on-dark-muted);line-height:1.7}
.foot-bar{display:flex;flex-wrap:wrap;gap:var(--sp-4);justify-content:space-between;
  margin-top:var(--sp-12);padding-top:var(--sp-5);border-top:1px solid var(--border-on-dark);
  color:var(--text-faint);font-size:var(--fs-xs)}
.foot-logo{height:28px;width:auto;margin-bottom:var(--sp-5);opacity:.9}

/* reveal on enter — one authored entrance, not per-element confetti */
.reveal{opacity:0;transform:translateY(18px)}
.reveal.in{opacity:1;transform:none;
  transition:opacity 620ms var(--ease-out),transform 620ms var(--ease-out)}

/* ---------- SVG stage primitives ---------- */
.part{opacity:0}                 /* driven by JS */
.lbl{font-family:var(--font-body);font-size:13px;font-weight:500;fill:var(--text-on-dark-muted);
  letter-spacing:.02em}
.lbl--n{font-family:var(--font-display);font-variant-numeric:tabular-nums;fill:var(--azure-700)}
.bench-plate{fill:var(--navy-900);stroke:rgba(14,19,36,.15)}
.metal{fill:#2a3560;stroke:#59679c;stroke-width:1}
.metal-2{fill:#1d264a;stroke:#4a5788;stroke-width:1}
.glass{fill:rgba(0,159,227,.14);stroke:var(--azure-400);stroke-width:1}
.beam{stroke:var(--laser-785);stroke-width:2.5;stroke-linecap:round}
.beam-soft{stroke:var(--laser-785);stroke-width:7;opacity:.16;stroke-linecap:round}
.beam-raman{stroke:var(--azure-400);stroke-width:2;stroke-linecap:round}
.grid-line{stroke:rgba(14,19,36,.08);stroke-width:1}
.spec-line{fill:none;stroke:var(--azure-400);stroke-width:2;stroke-linejoin:round}

/* ---------- responsive ---------- */
@media (max-width:1080px){
  .stage-inner{gap:var(--sp-6);align-content:center}
  .stage-note{display:none}
  .head{grid-template-columns:minmax(0,1fr);gap:var(--sp-5)}
  .hero-grid{grid-template-columns:minmax(0,1fr)}
  .hero-meta{flex-direction:row;flex-wrap:wrap;gap:var(--sp-8);border-left:0;padding-left:0;
    border-top:1px solid var(--border-on-dark);padding-top:var(--sp-6)}
  .cta-in{grid-template-columns:minmax(0,1fr)}
  .foot-grid{grid-template-columns:repeat(2,minmax(0,1fr))}
  .card--wide{grid-column:auto}
}
@media (max-width:760px){
  :root{--nav-h:56px}
  .nav-links{position:fixed;inset:var(--nav-h) 0 auto 0;background:var(--navy-950);
    flex-direction:column;align-items:stretch;gap:0;padding:var(--sp-2);
    border-bottom:1px solid var(--border-on-dark);display:none}
  .nav-links.open{display:flex}
  .nav-links a{padding:var(--sp-4)}
  .nav-links .btn{margin:var(--sp-2);justify-content:center}
  .nav-toggle{display:inline-flex;margin-left:auto;background:none;border:1px solid rgba(14,19,36,.22);
    color:var(--text-on-dark);border-radius:var(--r-sm);padding:var(--sp-2) var(--sp-3);
    font-size:var(--fs-xs);letter-spacing:var(--ls-label);text-transform:uppercase;cursor:pointer}
  .stage-pin{height:100svh;padding-bottom:60px}
  .stage-vis{max-height:34svh}
  .stage-vis svg{max-height:34svh}
  .lbl{display:none}
  .step h3{font-size:1.375rem}
  .step .figs{gap:var(--sp-2) var(--sp-5)}
  .rail-label{display:none}
  .foot-grid{grid-template-columns:minmax(0,1fr)}
  .faq .a{padding-right:0}
  p,.step p{max-width:none}
}
@media (prefers-reduced-motion:reduce){
  html{scroll-behavior:auto}
  *,*::before,*::after{animation-duration:.01ms !important;transition-duration:.01ms !important}
}

/* initial state for scroll-driven parts (avoids a flash before JS paints) */
.stage [data-anim]{opacity:0}
.stage [data-anim~="dim"],.stage [data-anim~="out"]{opacity:1}
.stage.is-static [data-anim]{opacity:1 !important}

/* stacked share bar — measurement architecture */
.share{display:flex;height:44px;border-radius:var(--r-sm);overflow:hidden;border:1px solid var(--border-on-dark)}
.share i{display:block;position:relative}
.share-key{display:grid;grid-template-columns:repeat(auto-fit,minmax(11rem,1fr));gap:var(--sp-4) var(--sp-6);margin-top:var(--sp-6)}
.share-key div{border-top:2px solid currentColor;padding-top:var(--sp-3)}
.share-key b{display:block;font-family:var(--font-display);font-size:1.25rem;font-variant-numeric:tabular-nums;color:var(--text-on-dark)}
.share-key span{font-size:var(--fs-sm);color:var(--text-on-dark-muted)}

/* differentiator blocks — deliberately uneven rhythm */
.diffs{display:grid;grid-template-columns:repeat(6,1fr);gap:var(--sp-6)}
.diffs > *{grid-column:span 3}
.diffs > .w2{grid-column:span 2}
.diffs > .w4{grid-column:span 4}
.diffs > .w6{grid-column:span 6}
@media (max-width:900px){.diffs{grid-template-columns:1fr}.diffs > *{grid-column:auto !important}}
.diff h4{font-size:1.125rem}
.diff{padding-top:var(--sp-5);border-top:1px solid var(--border-hairline)}
.diff p{font-size:var(--fs-sm);color:var(--text-muted);margin:0}
.section:not(.section--light) .diff{border-color:var(--border-on-dark)}
.section:not(.section--light) .diff h4{color:var(--text-on-dark)}
.section:not(.section--light) .diff p{color:var(--text-on-dark-muted)}
.diff .tier{font-size:var(--fs-xs);color:var(--indigo-600);font-weight:var(--fw-semibold);
  display:block;margin-bottom:var(--sp-2);font-variant-numeric:tabular-nums}

/* rail ticks double as step jumps (keyboard / clicker friendly) */
.rail-ticks i{cursor:pointer}
.rail-ticks i:hover{background:var(--azure-400)}
.rail-ticks i:focus-visible{outline:2px solid var(--azure-400);outline-offset:3px}

/* reduced-motion fallback: keep the assembled diagram at a readable size */
.stage.is-static .stage-vis{max-width:960px}

/* ---------- engineering drawing sheet ----------
   The insertion/retraction drawing is reproduced as supplied by Gekko (white sheet,
   hatched sections, monospace annotation) — a deliberate contrast to the dark page. */
.dwg{background:#fff;border:1px solid var(--steel-200);border-radius:var(--r-lg);overflow:hidden;
  box-shadow:var(--shadow-lg)}
.dwg-top{display:flex;justify-content:space-between;align-items:center;gap:var(--sp-4);
  padding:var(--sp-3) var(--sp-5);border-bottom:1px solid #e8ebef;background:#f2f8fd;
  font-size:var(--fs-xs);color:#55606b;font-variant-numeric:tabular-nums}
.dwg-top b{font-family:var(--font-display);letter-spacing:var(--ls-label);text-transform:uppercase;
  color:var(--azure-700);font-weight:var(--fw-semibold)}
.dwg-body{padding:var(--sp-3)}
.dwg svg{width:100%;height:auto;display:block;background:#fff;
  font-family:"Consolas","DejaVu Sans Mono","Courier New",monospace}
.dwg .ts{font-size:11.5px;fill:#55606b;letter-spacing:.2px}
.dwg .tag{font-size:11.5px;fill:#1a1a1a;font-weight:700;letter-spacing:.3px}
.dwg .leader{stroke:#5a6570;stroke-width:.75}
.dwg .arr{stroke:#1a1a1a}
.dwg #boregroup{transform-origin:340px 320px}
@media (max-width:1080px){ .dwg-body{padding:var(--sp-2)} }

/* wide stage variant — the plant map needs the full column width to stay legible */
.stage--wide .stage-inner{grid-template-columns:minmax(0,1fr);gap:var(--sp-6)}
.stage--wide .stage-copy{min-height:13rem}
.stage--wide .step p{max-width:64ch}
.stage--wide .step .figs{margin-top:var(--sp-4);padding-top:var(--sp-3)}
@media (max-width:1080px){ .stage--wide .stage-copy{min-height:15rem} }