/* ==========================================================================
   Base - reset, typography, atmosphere, chrome, primitives
   ========================================================================== */

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: 6rem;
  -webkit-text-size-adjust: 100%;
  /* Must sit on the scroll container as well as body. With it on body alone,
     the html element still scrolls horizontally and the guard does nothing. */
  overflow-x: hidden;
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
}

body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: var(--font-body);
  font-size: var(--text-base);
  line-height: var(--leading-body);
  font-weight: 400;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  overflow-x: hidden;
}

img, svg, video { display: block; max-width: 100%; height: auto; }
button, input, select, textarea { font: inherit; color: inherit; }

/* --- Atmosphere -----------------------------------------------------------
   A fixed layered field: a warm signal bloom top-left, a cold data bloom
   bottom-right, and a fine grain overlay. Fixed so the page content parallaxes
   against a stable light source, the way a set is lit rather than a page
   being decorated. */

.atmosphere {
  position: fixed;
  inset: 0;
  z-index: 0;
  pointer-events: none;
  /* The bloom layer below is inset -20% to keep its gradient edges off-screen.
     Without clipping here that bleed widens the document and creates a
     horizontal scrollbar. */
  overflow: hidden;
}

.atmosphere::before {
  content: "";
  position: absolute;
  inset: -20%;
  background:
    radial-gradient(48rem 40rem at 12% -4%, oklch(77% 0.117 242 / 0.13), transparent 62%),
    radial-gradient(52rem 44rem at 96% 88%, oklch(74% 0.082 205 / 0.10), transparent 60%),
    radial-gradient(38rem 32rem at 62% 42%, oklch(30% 0.02 255 / 0.55), transparent 70%);
}

/* Grain: an SVG feTurbulence tile, kept at low opacity. Gives the dark field
   a photographic surface instead of a flat digital void. */
.atmosphere::after {
  content: "";
  position: absolute;
  inset: 0;
  opacity: 0.055;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='140' height='140'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.85' numOctaves='3'/%3E%3C/filter%3E%3Crect width='140' height='140' filter='url(%23n)'/%3E%3C/svg%3E");
}

/* --- Typography ---------------------------------------------------------- */

h1, h2, h3, h4 { margin: 0; font-weight: 400; }

.display {
  font-family: var(--font-display);
  font-weight: 400;
  letter-spacing: var(--tracking-tight);
  line-height: var(--leading-tight);
}

.display em {
  font-style: italic;
  color: var(--signal);
}

h1.display { font-size: var(--text-h1); }
h2.display { font-size: var(--text-h2); line-height: var(--leading-snug); }
h3 { font-size: var(--text-h3); font-family: var(--font-display); line-height: var(--leading-snug); }

.eyebrow {
  font-family: var(--font-eyebrow);
  font-size: var(--text-xs);
  font-weight: 600;
  letter-spacing: var(--tracking-eyebrow);
  text-transform: uppercase;
  color: var(--text-dim);
}

.lead {
  font-size: var(--text-lead);
  line-height: 1.5;
  color: var(--bone-200);
  max-width: var(--measure);
}

.muted { color: var(--text-muted); }
.dim { color: var(--text-dim); }
.mono { font-family: var(--font-mono); font-variant-numeric: tabular-nums; }

p { margin: 0 0 var(--space-4); max-width: var(--measure); }
p:last-child { margin-bottom: 0; }

a { color: inherit; }

/* --- Layout primitives --------------------------------------------------- */

.shell {
  width: 100%;
  max-width: var(--max-w);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

.stack > * + * { margin-top: var(--space-4); }
.stack-lg > * + * { margin-top: var(--space-6); }

main { position: relative; z-index: 1; }

/* --- Compliance ticker ---------------------------------------------------
   Permanently visible. On a research-use-only site this is not decoration,
   it is the licence to operate, so it sits above the masthead and never
   scrolls away with it. */

.ticker {
  position: relative;
  z-index: 60;
  background: var(--signal-deep);
  color: var(--on-signal);
  overflow: hidden;
  border-bottom: 1px solid oklch(0% 0 0 / 0.3);
}

.ticker__track {
  display: flex;
  gap: var(--space-7);
  width: max-content;
  padding-block: 0.4rem;
  animation: ticker-slide 46s linear infinite;
}

.ticker:hover .ticker__track,
.ticker:focus-within .ticker__track { animation-play-state: paused; }

.ticker__item {
  font-family: var(--font-eyebrow);
  font-size: 0.6875rem;
  font-weight: 700;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  white-space: nowrap;
}

@keyframes ticker-slide {
  from { transform: translate3d(0, 0, 0); }
  to { transform: translate3d(-50%, 0, 0); }
}

@media (prefers-reduced-motion: reduce) {
  .ticker__track {
    animation: none;
    width: 100%;
    justify-content: center;
    flex-wrap: wrap;
    gap: var(--space-4);
    padding-inline: var(--gutter);
  }
  .ticker__item:nth-child(n + 5) { display: none; }
}

/* --- Masthead ------------------------------------------------------------ */

.masthead {
  position: sticky;
  top: 0;
  z-index: 50;
  backdrop-filter: blur(18px) saturate(1.4);
  background: oklch(15% 0.018 255 / 0.74);
  border-bottom: 1px solid transparent;
  transition: background var(--dur) var(--ease-out), border-colour var(--dur) var(--ease-out), border-color var(--dur) var(--ease-out);
}

.masthead[data-scrolled="true"] {
  background: oklch(15% 0.018 255 / 0.94);
  border-bottom-color: var(--hairline);
}

.masthead__inner {
  display: flex;
  align-items: center;
  gap: var(--space-5);
  min-height: 4.25rem;
}

.wordmark {
  display: flex;
  align-items: baseline;
  gap: 0.5rem;
  text-decoration: none;
  margin-right: auto;
}

.wordmark__name {
  font-family: var(--font-eyebrow);
  font-weight: 700;
  font-size: 0.9375rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
}

/* The colon is the one piece of brand punctuation - tinting it is what stops
   TRAINNORTH:LABS reading as a typo. */
.wordmark__sep {
  color: var(--signal);
  margin-inline: 0.04em;
}

.wordmark__mark {
  width: 0.5rem;
  height: 0.5rem;
  border-radius: 50%;
  background: var(--signal);
  box-shadow: 0 0 0 0 var(--signal-line);
  animation: pulse-mark 3.4s var(--ease-in-out) infinite;
}

@keyframes pulse-mark {
  0%, 100% { box-shadow: 0 0 0 0 var(--signal-line); }
  50% { box-shadow: 0 0 0 0.45rem oklch(77% 0.117 242 / 0); }
}

.nav {
  display: flex;
  gap: var(--space-5);
  align-items: center;
}

.nav a {
  font-family: var(--font-eyebrow);
  font-size: var(--text-xs);
  font-weight: 500;
  letter-spacing: 0.13em;
  text-transform: uppercase;
  text-decoration: none;
  color: var(--text-muted);
  padding-block: 0.5rem;
  position: relative;
  transition: color var(--dur-fast) var(--ease-out);
}

.nav a::after {
  content: "";
  position: absolute;
  left: 0;
  bottom: 0.15rem;
  width: 100%;
  height: 1px;
  background: var(--signal);
  transform: scaleX(0);
  transform-origin: right;
  transition: transform var(--dur) var(--ease-out);
}

.nav a:hover,
.nav a:focus-visible,
.nav a[aria-current="true"] { color: var(--text); }

.nav a:hover::after,
.nav a:focus-visible::after,
.nav a[aria-current="true"]::after {
  transform: scaleX(1);
  transform-origin: left;
}

@media (max-width: 900px) {
  .nav { display: none; }
}

/* Scroll progress rail - the reel counter for a documentary structure. */
.progress-rail {
  position: absolute;
  left: 0;
  bottom: 0;
  height: 2px;
  width: 100%;
  background: transparent;
}

.progress-rail__fill {
  height: 100%;
  width: 0%;
  background: linear-gradient(90deg, var(--signal-deep), var(--signal-bright));
  transition: width 90ms linear;
}

/* --- Buttons ------------------------------------------------------------- */

.btn {
  --btn-bg: transparent;
  --btn-fg: var(--text);
  --btn-border: var(--hairline-strong);
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  padding: 0.78rem 1.4rem;
  background: var(--btn-bg);
  color: var(--btn-fg);
  border: 1px solid var(--btn-border);
  border-radius: 999px;
  font-family: var(--font-eyebrow);
  font-size: var(--text-xs);
  font-weight: 600;
  letter-spacing: 0.13em;
  text-transform: uppercase;
  text-decoration: none;
  cursor: pointer;
  position: relative;
  overflow: hidden;
  transition: transform var(--dur-fast) var(--ease-out),
              border-color var(--dur-fast) var(--ease-out),
              color var(--dur-fast) var(--ease-out);
}

/* The wipe: a fill that sweeps from the left on hover. One considered
   interaction reused everywhere beats twenty different hover tricks. */
.btn::before {
  content: "";
  position: absolute;
  inset: 0;
  background: var(--signal);
  transform: scaleX(0);
  transform-origin: left;
  transition: transform var(--dur) var(--ease-out);
  z-index: -1;
}

.btn:hover, .btn:focus-visible { transform: translateY(-2px); }
.btn:hover::before, .btn:focus-visible::before { transform: scaleX(1); }
.btn:hover, .btn:focus-visible { color: var(--on-signal); border-color: var(--signal); }
.btn:active { transform: translateY(0); }

.btn--primary {
  --btn-bg: var(--signal);
  --btn-fg: var(--on-signal);
  --btn-border: var(--signal);
}
.btn--primary::before { background: var(--bone-100); }
.btn--primary:hover, .btn--primary:focus-visible { border-color: var(--bone-100); }

.btn--ghost { --btn-border: var(--hairline); }
.btn--sm { padding: 0.5rem 1rem; font-size: 0.6875rem; }

:where(a, button, input, select, [tabindex]):focus-visible {
  outline: 2px solid var(--signal);
  outline-offset: 3px;
  border-radius: var(--radius-sm);
}

/* --- Surfaces ------------------------------------------------------------ */

.card {
  background: var(--bg-card);
  border: 1px solid var(--hairline);
  border-radius: var(--radius-lg);
  padding: var(--space-5);
  backdrop-filter: blur(10px);
  transition: border-color var(--dur) var(--ease-out),
              transform var(--dur) var(--ease-out),
              box-shadow var(--dur) var(--ease-out);
}

.card:hover {
  border-color: var(--hairline-strong);
  transform: translateY(-3px);
  box-shadow: var(--shadow-lift);
}

.pill {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  padding: 0.28rem 0.7rem;
  border: 1px solid var(--hairline-strong);
  border-radius: 999px;
  font-family: var(--font-eyebrow);
  font-size: 0.6875rem;
  font-weight: 600;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  white-space: nowrap;
}

.pill__dot {
  width: 0.375rem;
  height: 0.375rem;
  border-radius: 50%;
  background: currentColor;
}

/* --- Reveal on scroll ---------------------------------------------------- */

[data-reveal] {
  opacity: 0;
  transform: translate3d(0, 1.75rem, 0);
  transition: opacity var(--dur-slow) var(--ease-out),
              transform var(--dur-slow) var(--ease-out);
  transition-delay: var(--reveal-delay, 0ms);
}

[data-reveal].is-revealed {
  opacity: 1;
  transform: translate3d(0, 0, 0);
}

@media (prefers-reduced-motion: reduce) {
  [data-reveal] { opacity: 1; transform: none; }
}

/* --- Screen reader ------------------------------------------------------- */

.sr-only {
  position: absolute;
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  white-space: nowrap;
  border: 0;
}

.skip-link {
  position: absolute;
  top: -100%;
  left: var(--gutter);
  z-index: 100;
  background: var(--signal);
  color: var(--on-signal);
  padding: 0.6rem 1rem;
  border-radius: 0 0 var(--radius) var(--radius);
  font-family: var(--font-eyebrow);
  font-size: var(--text-xs);
  font-weight: 700;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  text-decoration: none;
}

.skip-link:focus { top: 0; }