/* Certropy AI — design system and layout.
   Panels are pinned over a fixed WebGL stage; each chapter section is only scroll
   distance. Without JS the sections fall back to a normal document flow. */

:root {
  --abyss: #040a18;
  --abyss-rgb: 4, 10, 24; /* the same colour, for the scrims */
  --ink: #070c18;
  --ice: #eaf1ff;
  --ice-2: #c3d0ec;
  --mist: #b0bdd8;
  --dim: #74819f;
  --line: rgba(168, 194, 255, 0.14);
  --line-2: rgba(168, 194, 255, 0.3);
  --indigo: #263bff;
  --blue: #136dff;
  --sky: #00a6ff;
  --cyan: #00d2d8;
  --ember: #e46a1a;
  --ember-hi: #ff8f45;
  --signal: #7fd4ff;
  /* callout leader lines and anchor marks, as RGB triplets for the HUD canvas */
  --callout-line: 190, 214, 255;
  --callout-mark: 226, 238, 255;

  --m: clamp(20px, 2.6vw, 44px);
  /* type scale: display, chapter heading, body, label */
  --fs-display: clamp(46px, min(6vw, 11vh), 112px);
  --fs-h2: clamp(28px, min(3.2vw, 6.2vh), 56px);
  --fs-body: clamp(14.5px, 1vw, 16px);
  --fs-label: 12px;
  --font-sans: "Geist", "Certropy SC", "PingFang SC", "Hiragino Sans GB", "Microsoft YaHei", system-ui, sans-serif;
  --font-mono: "Martian Mono", "Certropy SC", ui-monospace, "Cascadia Mono", Consolas, monospace;
  --ease-out: cubic-bezier(0.16, 1, 0.3, 1);
  --ease-io: cubic-bezier(0.65, 0, 0.35, 1);
}

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

html {
  background: var(--abyss);
  color: var(--ice);
  font-family: var(--font-sans);
  font-size: 16px;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  text-rendering: optimizeLegibility;
  -webkit-text-size-adjust: 100%;
}
html.js { scroll-snap-type: y proximity; }
html.is-loading { overflow: hidden; }

body { margin: 0; min-height: 100%; overflow-x: hidden; }
img { display: block; max-width: 100%; }
a { color: inherit; text-decoration: none; }
button { font: inherit; color: inherit; background: none; border: 0; padding: 0; cursor: pointer; }
h1, h2, h3, p, ul, ol { margin: 0; padding: 0; }
ul, ol { list-style: none; }

::selection { background: rgba(0, 166, 255, 0.35); color: #fff; }
:focus-visible { outline: 1px solid var(--signal); outline-offset: 4px; }

.mono {
  font-family: var(--font-mono);
  font-stretch: 87.5%;
  font-size: 10.5px;
  letter-spacing: 0.04em;
}

.skip {
  position: fixed; left: var(--m); top: 12px; z-index: 200;
  padding: 8px 12px; background: var(--ice); color: var(--abyss);
  transform: translateY(-160%); transition: transform 0.3s var(--ease-out);
}
.skip:focus { transform: none; }

/* ───────────── Stage layers ───────────── */

.gl, .hud-lines {
  position: fixed; left: 0; top: 0;
  width: 100vw; height: 100vh; height: 100lvh;
  display: block;
}
.gl { z-index: 0; }
.hud-lines { z-index: 3; pointer-events: none; }
.callouts { position: fixed; inset: 0; z-index: 4; pointer-events: none; }

.gl-fallback {
  position: fixed; inset: 0; z-index: 0; display: none;
  place-items: center;
  background:
    radial-gradient(60vmax 50vmax at 62% 46%, rgba(19, 109, 255, 0.22), transparent 60%),
    radial-gradient(30vmax 30vmax at 62% 46%, rgba(228, 106, 26, 0.12), transparent 60%),
    linear-gradient(180deg, #060a16, var(--abyss));
}
.gl-fallback img { width: min(58vmin, 560px); margin-left: 24vw; filter: drop-shadow(0 0 40px rgba(0, 166, 255, 0.35)); }
.no-webgl .gl-fallback { display: grid; }
.no-webgl .gl { display: none; }

/* ───────────── Loader ───────────── */

.loader {
  position: fixed; inset: 0; z-index: 100;
  display: grid; place-content: center; justify-items: center; gap: 28px;
  background: var(--abyss);
  transition: opacity 1.1s var(--ease-io), visibility 0s linear 1.1s;
}
.loader.is-done { opacity: 0; visibility: hidden; }
.loader-mark { width: 196px; height: 196px; overflow: visible; }
.loader-mark rect { opacity: 0.12; transition: opacity 0.5s var(--ease-out), filter 0.5s; }
.loader-mark rect.on { opacity: 1; }
.loader-mark path { opacity: 0; transition: opacity 0.6s var(--ease-out); }
.loader-mark.is-core path { opacity: 1; filter: drop-shadow(0 0 18px rgba(255, 120, 40, 0.9)); }
.loader-line {
  display: flex; gap: 40px; align-items: baseline;
  font-family: var(--font-mono); font-stretch: 87.5%; font-size: 10.5px; letter-spacing: 0.06em;
  color: var(--mist);
}
.loader-name { font-family: var(--font-sans); font-size: 12px; letter-spacing: 0.12em; }
.loader-pct { color: var(--ice); font-size: 11px; font-variant-numeric: tabular-nums; }
.loader-pct i { font-style: normal; color: var(--dim); margin-left: 2px; }
.loader-bar { width: 220px; height: 1px; background: var(--line); overflow: hidden; }
.loader-bar i { display: block; height: 100%; width: 100%; background: var(--ice); transform-origin: 0 50%; transform: scaleX(0); }

/* ───────────── HUD ───────────── */

.hud { position: fixed; z-index: 20; }
.js .hud { opacity: 0; transition: opacity 1.4s var(--ease-io) 0.3s; }
.js.is-ready .hud { opacity: 1; }

.hud-top {
  left: 0; right: 0; top: 0; z-index: 40;
  display: flex; align-items: flex-start; justify-content: space-between;
  padding: 24px var(--m) 0;
  pointer-events: none;
}
.hud-top > * { pointer-events: auto; }

.brand { display: flex; align-items: center; gap: 16px; }
.brand-mark { width: 52px; height: 52px; margin: -5px -3px -5px -8px; }
.brand-text { display: grid; gap: 5px; line-height: 1; }
.brand-text b { font-weight: 600; font-size: 19.5px; letter-spacing: 0.18em; }
.brand-text i {
  font-style: normal; font-size: 12.5px; font-weight: 400; letter-spacing: 0.12em; color: var(--mist);
}

.nav { display: flex; gap: clamp(18px, 2.2vw, 36px); margin-top: 6px; }
.nav a {
  position: relative; padding: 6px 0;
  font-size: 13px; letter-spacing: 0.14em; color: var(--mist);
  transition: color 0.4s var(--ease-out);
}
.nav a::after {
  content: ""; position: absolute; left: 0; right: 0.14em; bottom: 0; height: 1px;
  background: var(--ice); transform: scaleX(0); transform-origin: 0 50%;
  transition: transform 0.5s var(--ease-out);
}
.nav a:hover { color: var(--ice); }
.nav a:hover::after { transform: scaleX(1); }
.nav a.is-current { color: var(--ice); }
.nav a.is-current::after { transform: scaleX(1); background: var(--sky); }

.hud-tools { display: flex; gap: 14px; align-items: center; margin-top: 6px; }
.tool {
  font-size: var(--fs-label); letter-spacing: 0.08em;
  color: var(--mist); padding: 6px 2px; transition: color 0.3s;
}
.tool:hover { color: var(--ice); }
.lang { display: inline-flex; gap: 6px; }
.lang-on { color: var(--ice); }
.lang-sep { color: var(--dim); }
.menu-btn { display: none; }

.hud-rail { right: calc(var(--m) - 6px); top: 50%; transform: translateY(-50%); }
.hud-rail ol { display: grid; gap: 14px; justify-items: end; }
.hud-rail li {
  display: flex; align-items: center; gap: 10px; cursor: pointer;
  font-size: var(--fs-label); letter-spacing: 0.1em; color: var(--dim);
  transition: color 0.4s;
}
.hud-rail li span { order: -1; opacity: 0; transform: translateX(6px); transition: opacity 0.4s, transform 0.5s var(--ease-out); }
.hud-rail li i { display: block; width: 12px; height: 1px; background: currentColor; transition: width 0.6s var(--ease-out), background 0.4s; }
.hud-rail li:hover span { opacity: 1; transform: none; }
.hud-rail li:hover { color: var(--ice); }
.hud-rail li.is-current { color: var(--ice); }
.hud-rail li.is-current i { width: 28px; background: var(--sky); }

.hud-bottom {
  left: 0; right: 0; bottom: 0;
  display: grid; grid-template-columns: 1fr auto 1fr; align-items: end;
  padding: 0 var(--m) 22px;
  pointer-events: none;
  font-size: var(--fs-label); letter-spacing: 0.06em; color: var(--mist);
}
.hud-bottom button { pointer-events: auto; }
.hud-chapter { display: flex; align-items: baseline; gap: 14px; }
.hud-index { font-family: var(--font-mono); font-stretch: 87.5%; font-size: 10.5px; color: var(--dim); font-variant-numeric: tabular-nums; }
.hud-index b { font-weight: 400; color: var(--ice); font-size: 12px; }
.hud-title { font-size: var(--fs-label); letter-spacing: 0.16em; color: var(--ice-2); }

.hud-scroll { display: grid; justify-items: center; gap: 10px; color: var(--dim); transition: opacity 0.6s; }
.hud-scroll i { position: relative; display: block; width: 1px; height: 34px; background: var(--line); overflow: hidden; }
.hud-scroll i::after {
  content: ""; position: absolute; left: 0; top: 0; width: 1px; height: 12px; background: var(--ice);
  animation: scrollcue 2.4s var(--ease-io) infinite;
}
@keyframes scrollcue { 0% { transform: translateY(-14px); } 60%, 100% { transform: translateY(36px); } }
.hud-scroll.is-hidden { opacity: 0; }

.hud-readout { display: flex; justify-content: flex-end; align-items: baseline; gap: 22px; }
.readout b { font-family: var(--font-mono); font-stretch: 87.5%; font-size: 11px; font-weight: 400; color: var(--ice); font-variant-numeric: tabular-nums; margin: 0 2px; }
.sound { display: inline-flex; align-items: center; gap: 8px; padding: 0; }
.sound-bars { display: inline-flex; align-items: flex-end; gap: 2px; height: 9px; }
.sound-bars i { display: block; width: 1px; height: 3px; background: currentColor; transition: height 0.3s; }
.sound.is-on { color: var(--ice); }
.sound.is-on .sound-bars i { animation: eq 1.1s var(--ease-io) infinite alternate; }
.sound.is-on .sound-bars i:nth-child(2) { animation-delay: -0.4s; }
.sound.is-on .sound-bars i:nth-child(3) { animation-delay: -0.8s; }
.sound.is-on .sound-bars i:nth-child(4) { animation-delay: -0.2s; }
@keyframes eq { from { height: 2px; } to { height: 9px; } }
/* the autoplay switch: a track, with one block of the logo for a thumb */
.auto { position: relative; display: inline-flex; align-items: center; gap: 8px; padding: 6px 0; margin: -6px 0; }
.auto-switch {
  position: relative; display: block; width: 24px; height: 12px;
  border: 1px solid var(--line-2); border-radius: 3px;
  transition: border-color 0.3s, background 0.3s;
}
.auto-switch i {
  position: absolute; left: 2px; top: 2px; width: 6px; height: 6px; border-radius: 1px;
  background: var(--mist);
  transition: transform 0.35s var(--ease-out), background 0.3s;
}
.auto[aria-checked="true"] { color: var(--ice); }
.auto[aria-checked="true"] .auto-switch { border-color: rgba(127, 212, 255, 0.7); background: rgba(19, 109, 255, 0.24); }
.auto[aria-checked="true"] .auto-switch i { transform: translateX(12px); background: var(--ice); }
/* the current wait: how long this chapter holds, or how long until it carries on */
.auto::after {
  content: ""; position: absolute; left: 0; right: 0; bottom: 0; height: 1px;
  background: var(--signal); opacity: 0;
  transform: scaleX(var(--p, 0)); transform-origin: 0 50%;
  transition: opacity 0.3s;
}
.auto[data-state="dwell"]::after, .auto[data-state="hold"]::after { opacity: 0.85; }

/* Menu (small screens) */
.menu {
  position: fixed; inset: 0; z-index: 30;
  display: grid; align-content: center; padding: 0 var(--m);
  background: rgba(var(--abyss-rgb), 0.92); backdrop-filter: blur(14px);
}
.menu[hidden] { display: none; }
.menu ol { display: grid; gap: 4px; }
.menu a { display: flex; align-items: baseline; gap: 18px; padding: 10px 0; font-size: 28px; letter-spacing: 0.1em; border-bottom: 1px solid var(--line); }
.menu .mono { color: var(--dim); }

/* ───────────── Callouts (3D-anchored labels) ───────────── */

.callout {
  position: absolute; left: 0; top: 0;
  text-shadow: 0 0 10px rgba(var(--abyss-rgb), 0.95), 0 0 22px rgba(var(--abyss-rgb), 0.8);
  display: grid; gap: 3px;
  white-space: nowrap;
  opacity: 0; transition: opacity 0.5s var(--ease-out);
  will-change: transform;
}
.callout.is-on { opacity: 1; }
.callout b { font-weight: 500; font-size: 13.5px; letter-spacing: 0.1em; color: var(--ice); white-space: pre-line; }
.callout:lang(en) b { letter-spacing: 0.03em; line-height: 1.25; }
.callout i {
  font-style: normal; font-size: var(--fs-label); letter-spacing: 0.06em; color: var(--mist);
  font-variant-numeric: tabular-nums;
}
.callout.is-right { justify-items: end; text-align: right; }
.callout.is-hot b { color: #fff; }
.callout.is-hot i { color: var(--signal); }
.callout.is-core b { color: #fff; }
.callout.is-interactive { cursor: pointer; padding: 6px 8px; margin: -6px -8px; }
/* only a label that is on screen may catch the cursor */
.callout.is-interactive.is-on { pointer-events: auto; }

/* ───────────── Type ───────────── */

.t-hero {
  font-weight: 300;
  /* width sets the size; on short, wide screens the height caps it so the headline
     never crowds the stage */
  font-size: var(--fs-display);
  line-height: 1;
  letter-spacing: 0.02em;
  margin-left: -0.06em;
  white-space: nowrap;
}
/* one heading size for every chapter, capped by the viewport height so a chapter never
   runs under the header on short laptop screens */
.t-statement, .t-h2 {
  font-weight: 300;
  font-size: var(--fs-h2);
  line-height: 1.34;
  letter-spacing: 0.015em;
  white-space: pre-line;
}
.t-lead { font-size: clamp(15px, 1.1vw, 17.5px); line-height: 1.85; color: var(--ice-2); max-width: 31em; text-wrap: pretty; }
.t-body { font-size: var(--fs-body); line-height: 1.8; color: var(--mist); max-width: 32em; text-wrap: pretty; }
.cap-list p, .ver-list p, .assure p, .cov-items { text-wrap: pretty; }
h3 { font-weight: 500; font-size: 16px; letter-spacing: 0.08em; color: var(--ice); }

/* English type, by :lang() rather than the <html> attribute, so that the copy can be laid
   out in either language whatever the page shows (main.js measures both for the camera) */
.t-hero:lang(en) { font-weight: 300; letter-spacing: -0.035em; line-height: 0.98; font-size: clamp(42px, min(5.2vw, 9.6vh), 100px); white-space: pre-line; }
/* English runs wider: the hero headline breaks onto two lines before it reaches the logo */
.js .ch-hero .panel-in:lang(en) { width: min(46rem, 48vw); }
.t-statement:lang(en) { letter-spacing: -0.025em; line-height: 1.12; }
.t-h2:lang(en) { letter-spacing: -0.02em; line-height: 1.14; }
.t-lead:lang(en), .t-body:lang(en) { line-height: 1.65; }
.panel-in h3:lang(en) { letter-spacing: 0.01em; }
.nav a:lang(en), .brand-text b:lang(en) { letter-spacing: 0.04em; }

/* ───────────── Buttons ───────────── */

/* the primary action: solid ice with the ember block, the only orange outside the core */
.btn {
  position: relative; display: inline-flex; align-items: center; gap: 14px;
  padding: 15px 26px 15px 22px;
  font-size: 15px; font-weight: 500; letter-spacing: 0.12em; color: var(--abyss);
  background: var(--ice);
  border-radius: 2px;
  transition: background 0.4s var(--ease-out), gap 0.5s var(--ease-out);
}
.btn::before {
  content: ""; width: 7px; height: 7px; flex: none;
  background: var(--ember); transform: rotate(45deg);
}
.btn:hover { background: #fff; gap: 18px; }
.btn:focus-visible { outline-offset: 5px; }
.btn-lg { padding: 18px 32px 18px 26px; font-size: 16px; }

.btn-quiet {
  position: relative; font-size: 14.5px; letter-spacing: 0.12em; color: var(--ice-2);
  padding: 8px 0; transition: color 0.4s;
}
.btn-quiet::after {
  content: ""; position: absolute; left: 0; right: 0.12em; bottom: 2px; height: 1px;
  background: currentColor; transform-origin: 100% 50%; transition: transform 0.5s var(--ease-out);
}
.btn-quiet:hover { color: var(--ice); }
.btn-quiet:hover::after { transform: scaleX(0.3); }

.btn:lang(en), .btn-quiet:lang(en) { letter-spacing: 0.02em; }

/* ───────────── Chapters ───────────── */

.ch { position: relative; }
.panel { position: relative; }
.panel-in { position: relative; }

.js .ch { height: 140vh; scroll-snap-align: start; }
.js .ch:last-child { height: 100vh; }
/* Inactive panels are transparent rather than hidden, so screen readers still reach every
   chapter; focus moving into one scrolls the page to it (see main.js). */
.js .panel { position: fixed; inset: 0; z-index: 5; pointer-events: none; opacity: 0; }
.js .ch.is-active .panel, .js .ch.is-leaving .panel { opacity: 1; }
.js .panel-in { position: absolute; pointer-events: none; }
.js .ch.is-active .panel-in { pointer-events: auto; }

/* soft scrims keep copy legible over the stage */
.js .panel::before {
  content: ""; position: absolute; inset: 0; pointer-events: none;
  opacity: 0; transition: opacity 0.9s var(--ease-out);
}
.js .ch.is-active .panel::before { opacity: 1; }
.ch-hero .panel::before { background: radial-gradient(64vw 74vh at 0% 82%, rgba(var(--abyss-rgb), 0.74), rgba(var(--abyss-rgb), 0.3) 52%, transparent 74%); }
.ch-thesis .panel::before { background: radial-gradient(44vw 30vh at 50% 50%, rgba(var(--abyss-rgb), 0.78), rgba(var(--abyss-rgb), 0.4) 55%, transparent 78%); }
.ch-cap .panel::before { background: linear-gradient(90deg, rgba(var(--abyss-rgb), 0.74), rgba(var(--abyss-rgb), 0.4) 34%, transparent 54%); }
.ch-ver .panel::before { background: linear-gradient(270deg, rgba(var(--abyss-rgb), 0.76), rgba(var(--abyss-rgb), 0.42) 36%, transparent 56%); }
.ch-cov .panel::before { background: linear-gradient(90deg, rgba(var(--abyss-rgb), 0.72), rgba(var(--abyss-rgb), 0.36) 30%, transparent 48%); }
.ch-team .panel::before { background: linear-gradient(90deg, rgba(var(--abyss-rgb), 0.7), transparent 52%); }
.ch-contact .panel::before { background: linear-gradient(0deg, rgba(var(--abyss-rgb), 0.88), rgba(var(--abyss-rgb), 0.45) 42%, transparent 62%); }

/* reveal: a left-to-right scan instead of fade-up. As a chapter comes in, main.js plays the
   scan itself (scan()), the same way, to keep it in step with the scene; these transitions
   play it otherwise, and play it out */
.js [data-reveal] {
  clip-path: inset(-20% 100% -20% 0);
  opacity: 0;
  transition: clip-path 1.1s var(--ease-out), opacity 0.6s var(--ease-out);
  transition-delay: calc(var(--d, 0) * 1ms);
}
.js .ch.is-active [data-reveal] { clip-path: inset(-20% -2% -20% 0); opacity: 1; }
.js .ch.is-leaving [data-reveal] { transition-duration: 0.4s, 0.35s; transition-delay: 0s; clip-path: inset(-20% -2% -20% 0); opacity: 0; }
.js .ch.is-leaving [data-decode] { opacity: 0; transition: opacity 0.35s; }
.js [data-decode] { transition: opacity 0.3s; }

/* hero */
.js .ch-hero .panel-in { left: var(--m); bottom: 16vh; width: min(52rem, 56vw); }
.ch-hero .t-lead { margin-top: 2rem; }
.hero-actions { display: flex; align-items: center; gap: 34px; margin-top: 2.6rem; }

/* thesis */
.js .ch-thesis .panel-in { left: 50%; top: 50%; width: min(64rem, 88vw); transform: translate(-50%, -50%); text-align: center; }
.ch-thesis .t-body { margin: 2.2rem auto 0; max-width: 36em; white-space: pre-line; }

/* capabilities: four services as one ruled list, the heading beside its line */
.js .ch-cap .panel-in { left: var(--m); top: 50%; transform: translateY(-50%); width: min(38rem, 40vw); }
.cap-list { margin-top: min(2.4rem, 4vh); display: grid; border-bottom: 1px solid var(--line); }
.cap-list li {
  display: grid; grid-template-columns: minmax(8.5em, 11em) 1fr; column-gap: 1.6rem; align-items: baseline;
  padding: min(1.05rem, 1.9vh) 0; border-top: 1px solid var(--line);
}
.cap-list p { font-size: 14px; line-height: 1.7; color: var(--mist); }

/* coverage: the copy and its colour key in one compact column on the left; the carousel
   is framed in the space to its right (camera.fit) */
.js .ch-cov .panel-in { left: var(--m); top: 50%; transform: translateY(-50%); width: min(28rem, 29vw); }
.ch-cov .t-body { margin-top: min(1.4rem, 2.4vh); font-size: 14.5px; }
.cov-legend { display: grid; gap: 0.9rem; margin-top: min(2.4rem, 4vh); }
.cov-group { display: grid; row-gap: 0.35rem; padding-top: 0.9rem; border-top: 1px solid var(--line); }
.cov-name { display: flex; align-items: center; gap: 10px; font-size: 15px; letter-spacing: 0.1em; color: var(--ice); }
/* colour key: the hue of that group's clusters on the carousel */
.cov-name::before { content: ""; width: 7px; height: 7px; flex: none; transform: rotate(45deg); background: var(--key); box-shadow: 0 0 10px var(--key); }
.cov-group.is-workflow { --key: var(--cyan); }
.cov-group.is-domain { --key: var(--blue); }
.cov-items { font-size: 13px; letter-spacing: 0.06em; color: var(--mist); padding-left: 17px; }

/* verification: mirrored, the rings on the left and the copy on the right; the three
   layers, then the delivery guarantees in a quieter row */
.js .ch-ver .panel-in { right: calc(var(--m) + 40px); top: 50%; transform: translateY(-50%); width: min(44rem, 46vw); }
.ch-ver .t-body { margin-top: min(1.2rem, 2vh); }
.ver-list { margin-top: min(2rem, 3.4vh); display: grid; border-bottom: 1px solid var(--line); }
.ver-list li {
  display: grid; grid-template-columns: minmax(6.5em, 8em) 1fr; column-gap: 1.6rem; align-items: baseline;
  padding: min(0.95rem, 1.7vh) 0; border-top: 1px solid var(--line);
}
.ver-list p { font-size: 14px; line-height: 1.7; color: var(--mist); }
.assure {
  margin-top: min(1.8rem, 3vh);
  display: grid; grid-template-columns: repeat(3, 1fr); column-gap: clamp(16px, 1.6vw, 28px);
}
.assure li { display: grid; gap: 0.4rem; align-content: start; }
.assure h3 { font-size: 13.5px; letter-spacing: 0.08em; color: var(--ice-2); }
.assure p { font-size: 12.5px; line-height: 1.65; color: var(--mist); }

/* team: the copy alone on the left; the network is the picture */
.js .ch-team .panel-in { left: var(--m); top: 50%; transform: translateY(-50%); width: min(36rem, 40vw); }
.ch-team .t-body { margin-top: min(1.6rem, 2.6vh); }

/* contact: sizes and gaps follow the viewport height, so the copy leaves the logo room */
.js .ch-contact .panel-in { left: 50%; bottom: 0; width: min(70rem, 92vw); transform: translateX(-50%); text-align: center; padding-bottom: min(92px, 12vh); }
.ch-contact .t-body { margin: min(1.4rem, 2.4vh) auto 0; max-width: 34em; white-space: pre-line; }
.contact-actions { display: flex; flex-wrap: wrap; justify-content: center; align-items: center; gap: 14px 28px; margin-top: min(2.4rem, 3.8vh); }
.contact-mail { position: relative; color: var(--ice-2); font-size: 14px; letter-spacing: 0.06em; }
/* "email us" (js/mail.js): a note stands in the address's place for a few seconds, and a
   line runs under it while the page waits for a mail app */
.mail-addr { transition: opacity 0.4s var(--ease-out); }
.mail-note {
  position: absolute; left: 0; top: 50%; transform: translateY(-50%);
  white-space: nowrap; color: var(--ice); opacity: 0; pointer-events: none;
  transition: opacity 0.4s var(--ease-out);
}
.contact-mail.is-noted .mail-addr { opacity: 0; }
.contact-mail.is-noted .mail-note { opacity: 1; }
.contact-mail::after {
  content: ""; position: absolute; left: 0; right: 0; bottom: -7px; height: 1px;
  background: var(--signal); opacity: 0; transform: scaleX(0); transform-origin: 0 50%;
  transition: opacity 0.3s, transform 0s 0.3s;
}
.contact-mail.is-waiting::after { opacity: 0.85; transform: scaleX(1); transition: opacity 0.3s, transform var(--wait, 2.5s) linear; }
.site-foot {
  display: flex; justify-content: center; flex-wrap: wrap; gap: 8px 28px; margin-top: min(3.2rem, 5vh);
  font-size: 11.5px; letter-spacing: 0.06em; color: var(--dim);
}
.site-foot a:hover { color: var(--ice-2); }
/* on a wide screen the legal line sits in the bottom HUD's row, between its two corners */
@media (min-width: 1000px) and (orientation: landscape) {
  .js .ch-contact .site-foot { position: absolute; left: 0; right: 0; bottom: 22px; margin: 0; }
}
/* in a narrower landscape window the line would run into the readout at the right, so it
   takes the row above the HUD corners instead; the English line is the longer one, and the
   copy above keeps clear of it on a short screen */
@media (min-width: 1000px) and (max-width: 1279px) and (orientation: landscape) {
  .js .ch-contact .site-foot:lang(en) { bottom: 44px; }
  .js .ch-contact .panel-in:lang(en) { padding-bottom: max(min(92px, 12vh), 74px); }
}
@media (min-width: 1000px) and (max-width: 1139px) and (orientation: landscape) {
  .js .ch-contact .site-foot { bottom: 44px; }
  .js .ch-contact .panel-in { padding-bottom: max(min(92px, 12vh), 74px); }
}

/* ───────────── Web mail chooser (js/mail.js) ───────────── */

/* for screen readers only */
.vh { position: absolute; width: 1px; height: 1px; overflow: hidden; clip-path: inset(50%); white-space: nowrap; font-style: normal; }

.mail-pick {
  width: min(35rem, calc(100vw - 32px)); max-width: none; max-height: calc(100dvh - 32px);
  margin: auto; padding: 24px 30px 22px;
  color: var(--ice);
  background: linear-gradient(180deg, #0c152c, #050a17);
  border: 1px solid rgba(168, 194, 255, 0.2); border-radius: 3px;
  box-shadow: 0 40px 120px rgba(0, 0, 0, 0.55);
  overflow: auto; overscroll-behavior: contain;
  opacity: 0; transform: translateY(10px);
  transition: opacity 0.24s var(--ease-out), transform 0.24s var(--ease-out);
}
.mail-pick.is-open { opacity: 1; transform: none; transition-duration: 0.5s; }
/* (the backdrop inherits no custom properties in older browsers: the abyss, spelled out) */
.mail-pick::backdrop { background: rgba(4, 10, 24, 0.66); opacity: 0; transition: opacity 0.24s; }
.mail-pick.is-open::backdrop { opacity: 1; transition-duration: 0.4s; }

.mail-pick-head { display: flex; justify-content: space-between; align-items: center; margin-right: -10px; }
/* the label leads with a tick, like the current chapter's in the nav and on the rail */
.mail-pick-label { display: flex; align-items: center; gap: 12px; font-size: var(--fs-label); letter-spacing: 0.16em; color: var(--mist); }
.mail-pick-label::before { content: ""; width: 20px; height: 1px; background: var(--sky); }
.mail-pick-close { position: relative; width: 32px; height: 32px; color: var(--mist); transition: color 0.3s; }
.mail-pick-close:hover { color: var(--ice); }
.mail-pick-close i, .mail-pick-close i::after { position: absolute; width: 14px; height: 1px; background: currentColor; }
.mail-pick-close i { left: 9px; top: 15.5px; transform: rotate(45deg); }
.mail-pick-close i::after { content: ""; left: 0; top: 0; transform: rotate(90deg); }

.mail-pick-title { margin-top: 12px; font-weight: 300; font-size: 26px; line-height: 1.3; letter-spacing: 0.04em; white-space: pre-line; }
.mail-pick-title:lang(en) { letter-spacing: -0.01em; }
.mail-pick-body { margin-top: 10px; font-size: 14px; line-height: 1.75; color: var(--mist); white-space: pre-line; text-wrap: pretty; }
.mail-pick-body:lang(en) { line-height: 1.6; }

.mail-pick-list { display: grid; grid-template-columns: repeat(3, 1fr); gap: 8px; margin-top: 22px; }
.mail-pick-item {
  position: relative; display: grid; gap: 6px; padding: 15px 30px 14px 16px;
  border: 1px solid var(--line); border-radius: 2px; background: rgba(168, 194, 255, 0.03);
  opacity: 0; transform: translateY(6px);
  transition: border-color 0.3s, background 0.3s,
    opacity 0.5s var(--ease-out) calc(140ms + var(--k, 0) * 45ms), transform 0.6s var(--ease-out) calc(140ms + var(--k, 0) * 45ms);
}
.mail-pick.is-open .mail-pick-item { opacity: 1; transform: none; }
/* line heights set, so a row of Chinese names and a row of Latin ones are the same height */
.mail-pick-item b { font-weight: 400; font-size: 15px; line-height: 22px; letter-spacing: 0.06em; color: var(--ice); white-space: nowrap; }
.mail-pick-item:lang(en) b { letter-spacing: 0.01em; }
.mail-pick-item span { font-size: 11px; line-height: 16px; letter-spacing: 0.04em; color: var(--dim); white-space: nowrap; }
.mail-pick-item svg {
  position: absolute; right: 13px; top: 17px; width: 10px; height: 10px;
  fill: none; stroke: currentColor; stroke-width: 1; color: var(--dim);
  transition: color 0.3s, transform 0.4s var(--ease-out);
}
.mail-pick-item:hover, .mail-pick-item:focus-visible { border-color: rgba(127, 212, 255, 0.5); background: rgba(19, 109, 255, 0.12); }
.mail-pick-item:hover svg, .mail-pick-item:focus-visible svg { color: var(--ice); transform: translate(2px, -2px); }
.mail-pick-item:focus-visible { outline-offset: 2px; }

.mail-pick-foot {
  display: flex; justify-content: space-between; align-items: center; gap: 8px 16px; flex-wrap: wrap;
  margin-top: 20px; padding-top: 14px; border-top: 1px solid var(--line);
}
.mail-pick-addr { font-size: 14px; letter-spacing: 0.06em; color: var(--ice-2); user-select: all; }
.mail-pick-copy { font-size: 13.5px; }

@media (max-width: 560px) {
  .mail-pick { padding: 20px 20px 18px; }
  .mail-pick-title { font-size: 22px; }
  .mail-pick-list { grid-template-columns: repeat(2, 1fr); margin-top: 18px; }
}

/* ───────────── No-JS flow ───────────── */

html:not(.js) .ch { min-height: 100vh; padding: 18vh var(--m) 12vh; border-top: 1px solid var(--line); }
html:not(.js) .gl-fallback { display: grid; opacity: 0.35; }
html:not(.js) .loader, html:not(.js) .hud-bottom, html:not(.js) .hud-rail { display: none; }
html:not(.js) .panel-in { max-width: 48rem; }


/* ───────────── Responsive ───────────── */

@media (max-width: 1100px) {
  .nav { display: none; }
  .menu-btn { display: inline-block; }
  .js .ch-cap .panel-in, .js .ch-ver .panel-in, .js .ch-team .panel-in { width: min(36rem, 48vw); }
  .js .ch-cov .panel-in { width: min(28rem, 38vw); }
}

/* Stacked layout for phones and portrait tablets: the subject sits in the upper half,
   the copy below it on a scrim. */
@media (max-width: 760px), (orientation: portrait) and (max-width: 1100px) {
  .hud-rail { display: none; }
  .js .ch { height: 135vh; }
  .js .ch:last-child { height: 100vh; }
  .js .panel-in {
    left: var(--m) !important; right: var(--m) !important; top: auto !important; bottom: 76px !important;
    width: auto !important; transform: none !important; text-align: left !important;
  }
  .js .panel::before {
    top: auto; height: 72vh;
    background: linear-gradient(180deg, rgba(var(--abyss-rgb), 0), rgba(var(--abyss-rgb), 0.78) 45%, rgba(var(--abyss-rgb), 0.92)) !important;
  }
  .ch-thesis .t-body, .ch-contact .t-body { margin-left: 0; }
  .cov-legend { margin-top: 1.4rem; }
  .contact-actions { justify-content: flex-start; }
  .site-foot { justify-content: flex-start; gap: 6px 18px; margin-top: 2rem; }
  .js .ch-contact .panel-in { padding-bottom: 0; }
}

@media (max-width: 760px) {
  :root { --m: 20px; }
  .brand { gap: 12px; }
  .brand-mark { width: 44px; height: 44px; }
  .brand-text b { font-size: 18px; }
  .brand-text i { font-size: 11px; }
  .hud-bottom { grid-template-columns: 1fr auto; padding-bottom: 16px; }
  .hud-scroll { display: none; }
  .hud-readout .readout { display: none; }

  .t-hero { font-size: clamp(44px, 13.5vw, 72px); }
  .t-statement, .t-h2 { font-size: clamp(26px, 7.2vw, 36px); }
  .ch-hero .t-lead { margin-top: 1.4rem; }
  .hero-actions { margin-top: 1.6rem; gap: 24px; }
  .ch-cap .t-h2, .ch-ver .t-h2 { font-size: clamp(24px, 6.6vw, 32px); }
  .cap-list { margin-top: 1.4rem; }
  .cap-list li { padding: 0.7rem 0; }
  .cap-list p, .ver-list p { font-size: 13px; line-height: 1.6; }
  .ch-cap .cap-list p { display: none; }
  .ver-list { margin-top: 1.4rem; }
  .ver-list li { padding: 0.75rem 0; }
  .ch-ver .t-body, .ch-ver .ver-list p { display: none; }
  .assure { grid-template-columns: 1fr; row-gap: 0.5rem; margin-top: 1rem; }
  .assure li { grid-template-columns: 8.4rem 1fr; }
  .assure p { font-size: 12.5px; line-height: 1.6; }
  /* the English descriptions run three lines each here, and would push the copy up into the rings */
  .ch-ver .assure p:lang(en) { display: none; }
  .callout b { font-size: 12px; }
  .callout i { display: none; }
}

/* short landscape screens, in English: its headings take two lines and its descriptions run
   longer, so the capabilities and verification lists close up to keep clear of the header */
@media (min-width: 761px) and (max-height: 700px) {
  .ch-cap .cap-list:lang(en) { margin-top: 14px; }
  .ch-cap .cap-list li:lang(en) { padding: 6px 0; }
  .ch-cap .cap-list p:lang(en) { line-height: 1.5; }
  .ch-ver .t-body:lang(en) { margin-top: 8px; }
  .ch-ver .ver-list:lang(en) { margin-top: 12px; }
  .ch-ver .ver-list li:lang(en) { padding: 5px 0; }
  .ch-ver .ver-list p:lang(en) { line-height: 1.5; }
  .ch-ver .assure:lang(en) { margin-top: 12px; }
  .ch-ver .assure p:lang(en) { line-height: 1.45; }
  /* and both sit in the middle of the band between the header and the bottom HUD, which is
     a little lower than the middle of the screen, as the header is the taller */
  .js .ch-cap .panel-in:lang(en), .js .ch-ver .panel-in:lang(en) { transform: translateY(calc(-50% + 16px)); }
}

/* very short landscape screens: the verification copy drops its descriptions to stay on screen */
@media (min-width: 761px) and (max-height: 500px) and (orientation: landscape) {
  .ch-ver .ver-list p, .ch-ver .assure p { display: none; }
  .ch-ver .ver-list li { grid-template-columns: 1fr; }
}

@media (prefers-reduced-motion: reduce) {
  html.js { scroll-snap-type: none; }
  *, *::before, *::after { animation-duration: 0.001ms !important; animation-iteration-count: 1 !important; }
  .js [data-reveal] { transition-duration: 0.2s !important; transition-delay: 0s !important; }
  .mail-pick, .mail-pick::backdrop, .mail-pick-item, .contact-mail::after { transition-duration: 0.01ms !important; transition-delay: 0s !important; }
}

/* decode effect: characters still resolving */
.dc { white-space: pre-wrap; }
.dc.is-scr { color: var(--signal); opacity: 0.75; }

/* social card capture (?og) */
.is-og .hud-bottom, .is-og .hud-rail, .is-og .nav, .is-og .hud-tools, .is-og .hero-actions { display: none !important; }