/* ============================================================
   Lab 01 — The Formation. Scroll-scrubbed cinema.
   The film section is a cinema: fixed deep-space palette in BOTH themes
   (a film doesn't change colour with the site). Everything after it
   returns to the shared design tokens in styles.css.
   Scrub engine: js/lab-formation.js — scroll progress drives
   video.currentTime; chapters carry data-from/data-to scroll windows.
   ============================================================ */

.film{
  position:relative;
  height:520vh; /* ~4 viewport-heights of scrub travel for the 8s film */
  background:#050508;
  color:#fff;
}
.film__stage{
  position:sticky;top:0;
  height:100vh;height:100dvh;
  overflow:hidden;
  /* iOS Safari leaves un-repainted "trails" of a sticky full-viewport <video>
     when scrolling back up. Promoting the stage to its own compositing layer
     and containing its paint to the box fixes the smear. (transform on the
     sticky element itself is safe — only a transformed *ancestor* breaks
     sticky.) */
  transform:translateZ(0);
  -webkit-backface-visibility:hidden;backface-visibility:hidden;
  contain:paint;
}
.film__video{
  position:absolute;inset:0;width:100%;height:100%;
  object-fit:cover;display:block;
  transform:translateZ(0); /* composite the video so scrubbed frames repaint cleanly */
  -webkit-backface-visibility:hidden;backface-visibility:hidden;
}
/* instant first-frame image (48KB) painted while the video downloads — this is
   the LCP element, so the section is never blank. Video stacks above it (later
   in the DOM) and covers it once the first frame decodes. */
.film__poster{
  position:absolute;inset:0;width:100%;height:100%;
  object-fit:cover;display:block;
  transform:translateZ(0);
}
/* guarantees caption legibility in the letterbox thirds, whatever the crop */
.film__vignette{
  position:absolute;inset:0;pointer-events:none;
  background:
    linear-gradient(180deg,rgba(5,5,8,.78),transparent 26%),
    linear-gradient(0deg,rgba(5,5,8,.82),transparent 34%);
}

/* dims the film under the centered title/end cards so they stay legible
   over bright frames — fades like house lights, driven by the engine */
.film__shade{
  position:absolute;inset:0;pointer-events:none;
  background:rgba(5,5,8,.62);opacity:0;transition:opacity .6s var(--ease);
}
.film--dim .film__shade{opacity:1}

/* ---------- loading state — telemetry voice ---------- */
.film__loader{
  position:absolute;inset:0;display:flex;flex-direction:column;gap:18px;
  align-items:center;justify-content:center;
  /* dark scrim over the poster frame — keeps the progress readout legible
     while the film downloads, without hiding the real first frame beneath */
  background:rgba(5,5,8,.6);
  transition:opacity .8s var(--ease),visibility .8s;
}
.film--ready .film__loader,
.film--static .film__loader{opacity:0;visibility:hidden}
.film__loader-line{
  width:min(220px,50vw);height:1px;background:rgba(255,255,255,.14);
  position:relative;overflow:hidden;
}
.film__loader-line::after{
  content:"";position:absolute;inset:0;background:#16C964;
  transform:translateX(-100%);animation:signal 1.6s var(--ease) infinite;
}
@keyframes signal{to{transform:translateX(100%)}}
.film__loader-text{
  font:500 12px var(--mono);letter-spacing:.14em;text-transform:uppercase;
  color:rgba(255,255,255,.55);
}
.film__loader-text b{color:#16C964;font-weight:500}

/* ---------- HUD ---------- */
.film__hud{
  position:absolute;top:calc(72px + 18px);left:0;right:0;
  display:flex;justify-content:space-between;
  padding:0 var(--pad);pointer-events:none;
  opacity:0;transition:opacity .6s var(--ease);
}
.film--ready .film__hud{opacity:1}
.film__hud-item{
  font:500 12px var(--mono);letter-spacing:.14em;text-transform:uppercase;
  color:rgba(255,255,255,.5);
  font-variant-numeric:tabular-nums; /* playhead digits don't jitter */
}

/* ---------- telemetry rail — the film's real phase timeline ---------- */
.film__rail{
  position:absolute;left:var(--pad);top:50%;transform:translateY(-50%);
  height:min(300px,38vh);pointer-events:none;
  opacity:0;transition:opacity .6s var(--ease);
}
.film--ready .film__rail{opacity:1}
.film__railline{
  position:absolute;left:0;top:0;bottom:0;width:1px;
  background:rgba(255,255,255,.16);
}
.film__railfill{
  position:absolute;left:0;top:0;width:100%;height:100%;
  background:#16C964;transform-origin:top;transform:scaleY(0);
}
.film__mark{
  position:absolute;left:0;transform:translateY(-50%);
  display:flex;align-items:center;gap:10px;white-space:nowrap;
  font:500 10px var(--mono);letter-spacing:.16em;text-transform:uppercase;
  color:rgba(255,255,255,.45);
}
.film__mark i{width:7px;height:1px;background:rgba(255,255,255,.4)}

/* ---------- chapters — captions in the lower letterbox third ---------- */
.filmchap{
  position:absolute;left:0;right:0;bottom:max(7dvh,34px);
  margin:0 auto;padding:0 var(--pad);max-width:820px;
  text-align:center;pointer-events:none;
}
.filmchap--center{
  bottom:auto;top:50%;transform:translateY(-50%);
}
.filmchap__eyebrow{
  font:500 12px var(--mono);letter-spacing:.16em;text-transform:uppercase;
  color:rgba(255,255,255,.55);margin:0 0 14px;
}
.filmchap__eyebrow--lit{color:#2BE072}
.filmchap__title{
  font:600 clamp(44px,8vw,96px)/1 var(--display);letter-spacing:-.03em;
  margin:0 0 20px;color:#fff;text-wrap:balance;
}
.filmchap__h{
  font:600 clamp(26px,4vw,44px)/1.1 var(--display);letter-spacing:-.02em;
  margin:0 0 14px;color:#fff;text-wrap:balance;
}
.filmchap__body{
  font:400 clamp(15px,1.7vw,18px)/1.6 var(--body);
  color:rgba(255,255,255,.78);margin:0 auto;max-width:620px;
}
/* the end card is a lower-third caption, but its frame (the ignited star)
   glows brightest dead-centre; a soft radial plate keeps the text readable
   over the lower bloom without boxing it in — the star's ring still shows. */
.filmchap--cta{
  padding-top:28px;padding-bottom:8px;
  background:radial-gradient(120% 150% at 50% 100%,rgba(5,5,8,.78),rgba(5,5,8,.4) 55%,transparent 78%);
  border-radius:24px;
}
.filmchap__actions{
  display:flex;gap:18px;align-items:center;justify-content:center;
  flex-wrap:wrap;margin-top:26px;
}
.filmchap__back{color:rgba(255,255,255,.85);border-color:rgba(255,255,255,.3)}
.filmchap__back:hover{color:#2BE072;border-color:#2BE072}

/* chapter choreography — driven by .is-on from the scrub engine */
.js .filmchap{
  opacity:0;transform:translateY(18px);visibility:hidden;
  transition:opacity .5s var(--ease),transform .5s var(--ease),visibility .5s;
}
.js .filmchap--center{transform:translate(0,calc(-50% + 18px))}
.js .filmchap.is-on{opacity:1;transform:translateY(0);visibility:visible}
.js .filmchap--center.is-on{transform:translate(0,-50%)}
.filmchap--cta.is-on{pointer-events:auto}

/* ---------- scroll hint ---------- */
.film__hint{
  position:absolute;left:50%;bottom:max(4dvh,20px);transform:translateX(-50%);
  display:flex;align-items:center;gap:10px;pointer-events:none;
  font:500 11px var(--mono);letter-spacing:.16em;text-transform:uppercase;
  color:rgba(255,255,255,.5);
  opacity:0;transition:opacity .5s var(--ease);
}
.film--ready .film__hint{opacity:1}
.film--ready .film__hint.is-hidden{opacity:0}
.film__hint svg{animation:hintdrop 2s var(--ease) infinite}
@keyframes hintdrop{0%,100%{transform:translateY(-3px);opacity:.5}50%{transform:translateY(3px);opacity:1}}

/* ---------- static fallback ----------
   Reduced motion, video failure, or no JS: no scrub, no sticky theatre.
   Chapters stack as a readable dark article over the starfield. */
.film--static,
html:not(.js) .film{height:auto}
.film--static .film__stage,
html:not(.js) .film__stage{
  position:static;height:auto;overflow:visible;
  display:flex;flex-direction:column;gap:clamp(40px,7vh,72px);
  padding:calc(72px + clamp(48px,8vw,96px)) 0 clamp(56px,9vw,104px);
  background:
    radial-gradient(1px 1px at 12% 28%,rgba(255,255,255,.5),transparent 100%),
    radial-gradient(1px 1px at 78% 18%,rgba(255,255,255,.35),transparent 100%),
    radial-gradient(1.5px 1.5px at 62% 66%,rgba(255,255,255,.4),transparent 100%),
    radial-gradient(1px 1px at 32% 82%,rgba(255,255,255,.3),transparent 100%),
    #050508;
}
.film--static .film__video,
.film--static .film__poster,
.film--static .film__vignette,
.film--static .film__shade,
.film--static .film__hud,
.film--static .film__rail,
.film--static .film__hint,
html:not(.js) .film__video,
html:not(.js) .film__poster,
html:not(.js) .film__vignette,
html:not(.js) .film__shade,
html:not(.js) .film__hud,
html:not(.js) .film__rail,
html:not(.js) .film__hint,
html:not(.js) .film__loader{display:none}
.film--static .filmchap,
html:not(.js) .filmchap{
  position:static;transform:none;opacity:1;visibility:visible;
  pointer-events:auto;
}
.js .film--static .filmchap{opacity:1;transform:none;visibility:visible}

/* ---------- specimen card (post-film, uses site tokens) ---------- */
.specimen{
  margin:44px 0 0;display:grid;gap:0;max-width:840px;
  border:1px solid var(--border);border-radius:20px;background:var(--bg);
  overflow:hidden;
}
.specimen__row{
  display:grid;grid-template-columns:minmax(150px,200px) 1fr;gap:20px;
  padding:20px 26px;border-top:1px solid var(--border);
}
.specimen__row:first-child{border-top:none}
.specimen__row dt{
  font:500 12px var(--mono);letter-spacing:.14em;text-transform:uppercase;
  color:var(--accent-ink);padding-top:3px;
}
.specimen__row dd{
  margin:0;font:400 16px/1.6 var(--body);color:var(--text-2);
}

/* ---------- responsive ---------- */
@media (max-width:900px){
  .film__rail{display:none}
  .film{height:440vh}
}
@media (max-width:640px){
  .film__hud{top:calc(72px + 10px)}
  .filmchap{bottom:max(5dvh,24px)}
  .filmchap__body{font-size:14.5px}
  .specimen__row{grid-template-columns:1fr;gap:8px;padding:18px 20px}
}

/* ---------- reduced motion ---------- */
@media (prefers-reduced-motion:reduce){
  .film__loader-line::after,.film__hint svg{animation:none}
}