:root {
  --bg: #060913;
  --bg-2: #0a0f1e;
  --ink: #e9edf6;
  --muted: #9aa4bb;
  --faint: #6b7590;
  --line: rgba(148, 163, 184, 0.16);
  --line-strong: rgba(148, 163, 184, 0.28);
  --cyan: #22d3ee;
  --cyan-soft: rgba(34, 211, 238, 0.14);
  --blue: #3b82f6;
  --violet: #8b5cf6;
  --amber: #fbbf24;
  --pink: #f472b6;
  --serif: 'Instrument Serif', Georgia, 'Times New Roman', serif;
  --sans: 'Space Grotesk', 'Inter', system-ui, -apple-system, 'Segoe UI', sans-serif;
  --body: 'Inter', system-ui, -apple-system, 'Segoe UI', sans-serif;
  --mono: 'IBM Plex Mono', ui-monospace, 'SF Mono', Menlo, monospace;
  --pad: clamp(1.25rem, 4vw, 3.5rem);
  --max: 1080px;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--ink);
  font-family: var(--body);
  font-size: 17px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  overflow-x: hidden;
}
a { color: var(--cyan); }

/* ---------- fixed backdrop ---------- */
#bg {
  position: fixed;
  inset: 0;
  width: 100%;
  height: 100%;
  z-index: 0;
  pointer-events: none;
}
.grain {
  position: fixed;
  inset: 0;
  z-index: 1;
  pointer-events: none;
  opacity: 0.05;
  mix-blend-mode: overlay;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='160' height='160'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.9' numOctaves='2'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
}

.progress {
  position: fixed;
  top: 0; left: 0;
  width: 100%;
  height: 2px;
  z-index: 5;
  background: rgba(148,163,184,0.12);
}
.progress span {
  display: block;
  height: 100%;
  width: 0;
  background: linear-gradient(90deg, var(--violet), var(--cyan));
  box-shadow: 0 0 12px var(--cyan);
}

/* ---------- layout ---------- */
main { position: relative; z-index: 1; }
.skip {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--cyan);
  color: #04121a;
  padding: 0.6rem 1rem;
  border-radius: 8px;
  font-weight: 600;
  text-decoration: none;
  z-index: 10;
}
.skip:focus { left: 1rem; top: 1rem; }

.hero {
  position: relative;
  min-height: 100vh;
  display: flex;
  flex-direction: column;
  justify-content: center;
  padding: var(--pad);
  max-width: var(--max);
  margin: 0 auto;
}
.hero__eyebrow { margin-bottom: 1.5rem; }
.hero__title {
  font-family: var(--serif);
  font-weight: 400;
  font-size: clamp(2.6rem, 8vw, 6.4rem);
  line-height: 0.98;
  letter-spacing: -0.02em;
  margin: 0 0 1.6rem;
  color: var(--ink);
  text-wrap: balance;
}
.hero__title em {
  font-style: italic;
  color: transparent;
  background: linear-gradient(120deg, var(--cyan), var(--violet));
  -webkit-background-clip: text;
  background-clip: text;
}
.hero__lead {
  font-size: clamp(1.05rem, 2.4vw, 1.35rem);
  color: var(--muted);
  max-width: 34rem;
  margin: 0 0 2.5rem;
}
.hero__cta {
  font-family: var(--mono);
  font-size: 0.8rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--faint);
}
.hero__cta-arrow {
  display: inline-block;
  animation: bob 1.8s ease-in-out infinite;
}
@keyframes bob { 0%,100% { transform: translateY(0); } 50% { transform: translateY(6px); } }

/* ---------- chapter ---------- */
.chapter { position: relative; }
.chapter__inner {
  max-width: var(--max);
  margin: 0 auto;
  padding: clamp(4rem, 12vh, 8rem) var(--pad);
}
.eyebrow {
  font-family: var(--mono);
  font-size: 0.74rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--cyan);
  margin: 0 0 1.1rem;
}
h2 {
  font-family: var(--sans);
  font-weight: 700;
  font-size: clamp(1.9rem, 4.6vw, 3.4rem);
  line-height: 1.04;
  letter-spacing: -0.015em;
  margin: 0 0 1.4rem;
  color: var(--ink);
  text-wrap: balance;
}
.lead {
  font-family: var(--serif);
  font-size: clamp(1.25rem, 3vw, 1.7rem);
  line-height: 1.4;
  color: #cdd5e4;
  max-width: 46rem;
  margin: 0 0 2rem;
}
.cols {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 2.5rem;
  color: var(--muted);
  max-width: 56rem;
}
.cols p { margin: 0; }
.lead em, .cols em, .lab__explain em { font-style: italic; color: var(--cyan); }

/* ---------- facts ---------- */
.facts {
  display: grid;
  grid-template-columns: repeat(2, 1fr);
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
  border-radius: 16px;
  overflow: hidden;
}
.fact {
  background: rgba(10, 15, 30, 0.55);
  padding: 1.75rem;
}
.fact h3 {
  font-family: var(--sans);
  font-size: 1.05rem;
  margin: 0 0 0.6rem;
  color: var(--ink);
}
.fact p { margin: 0; color: var(--muted); font-size: 0.95rem; }

/* ---------- footer ---------- */
.foot {
  position: relative;
  z-index: 1;
  max-width: var(--max);
  margin: 0 auto;
  padding: clamp(3rem, 8vh, 5rem) var(--pad) 4rem;
  border-top: 1px solid var(--line);
}
.refs { list-style: none; margin: 0 0 1.5rem; padding: 0; display: grid; gap: 0.65rem; }
.refs li { font-size: 0.9rem; color: var(--muted); }
.refs__who { color: var(--ink); font-weight: 600; }
.refs__where { color: var(--faint); font-style: italic; }
.foot__note { font-size: 0.85rem; color: var(--faint); max-width: 60rem; }

/* ---------- lab / decoder ---------- */
.lab {
  margin-top: 2rem;
  border: 1px solid var(--line);
  border-radius: 20px;
  background:
    radial-gradient(1200px 500px at 50% -10%, rgba(59,130,246,0.10), transparent 60%),
    rgba(7, 11, 22, 0.72);
  backdrop-filter: blur(6px);
  padding: clamp(1rem, 2.5vw, 1.75rem);
}
.lab__bar {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  flex-wrap: wrap;
  margin-bottom: 1rem;
}
.lab__modes { display: flex; gap: 0.4rem; }
.mode {
  font-family: var(--sans);
  font-size: 0.8rem;
  font-weight: 600;
  letter-spacing: 0.02em;
  color: var(--muted);
  background: rgba(148,163,184,0.06);
  border: 1px solid var(--line);
  border-radius: 999px;
  padding: 0.5rem 1rem;
  cursor: pointer;
  transition: all 0.2s ease;
}
.mode:hover { color: var(--ink); border-color: var(--line-strong); }
.mode.is-active {
  color: #04121a;
  background: var(--cyan);
  border-color: var(--cyan);
  box-shadow: 0 0 16px var(--cyan-soft);
}
.lab__readout {
  font-family: var(--mono);
  font-size: 0.78rem;
  color: var(--muted);
  margin: 0;
  min-height: 1.2em;
}
.lab__grid {
  display: grid;
  grid-template-columns: minmax(0, 1fr) 220px;
  gap: 1.25rem;
  align-items: start;
}
.lab__field { position: relative; }
.lab__canvas {
  width: 100%;
  height: auto;
  display: block;
  border-radius: 14px;
  background: rgba(4, 7, 14, 0.5);
  cursor: crosshair;
  touch-action: none;
}
.lab__hint {
  font-family: var(--mono);
  font-size: 0.72rem;
  color: var(--faint);
  margin: 0.6rem 0 0;
  text-align: center;
}

.lab__console {
  display: flex;
  flex-direction: column;
  gap: 1rem;
}
.ctl { display: block; }
.ctl__head {
  display: flex;
  justify-content: space-between;
  align-items: baseline;
  margin-bottom: 0.45rem;
}
.ctl__name { font-family: var(--sans); font-size: 0.82rem; color: var(--muted); }
.ctl output { font-family: var(--mono); font-size: 0.78rem; color: var(--cyan); }
.ctl input[type="range"] {
  -webkit-appearance: none;
  appearance: none;
  width: 100%;
  height: 4px;
  border-radius: 999px;
  background: var(--line);
  outline: none;
}
.ctl input[type="range"]::-webkit-slider-thumb {
  -webkit-appearance: none;
  appearance: none;
  width: 16px; height: 16px;
  border-radius: 50%;
  background: var(--cyan);
  border: 2px solid #04121a;
  cursor: pointer;
  box-shadow: 0 0 10px var(--cyan);
}
.ctl input[type="range"]::-moz-range-thumb {
  width: 14px; height: 14px; border-radius: 50%;
  background: var(--cyan); border: 2px solid #04121a; cursor: pointer;
}
.btn {
  font-family: var(--sans);
  font-size: 0.82rem;
  font-weight: 600;
  color: var(--ink);
  background: rgba(148,163,184,0.08);
  border: 1px solid var(--line-strong);
  border-radius: 10px;
  padding: 0.6rem 0.9rem;
  cursor: pointer;
  transition: all 0.2s ease;
}
.btn:hover { border-color: var(--cyan); color: var(--cyan); }
.lab__note { font-size: 0.72rem; color: var(--faint); margin: 0; line-height: 1.5; }

.lab__raster { margin-top: 1.25rem; }
.raster {
  width: 100%;
  height: auto;
  display: block;
  border-radius: 14px;
  background: rgba(4, 7, 14, 0.5);
  border: 1px solid var(--line);
}
.lab__raster-note {
  font-family: var(--mono);
  font-size: 0.7rem;
  color: var(--faint);
  margin: 0.55rem 0 0;
}
.lab__explain {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 2rem;
  color: var(--muted);
  margin-top: 1.5rem;
  padding-top: 1.25rem;
  border-top: 1px solid var(--line);
}
.lab__explain p { margin: 0; font-size: 0.95rem; }
.lab__explain strong { color: var(--ink); }

/* ---------- reveal ---------- */
.reveal, .chapter__inner > * {
  opacity: 1;
}
.chapter__inner {
  transition: none;
}
@media (prefers-reduced-motion: no-preference) {
  .chapter__inner {
    opacity: 0;
    transform: translateY(26px);
    transition: opacity 0.8s cubic-bezier(0.2, 0.65, 0.25, 1), transform 0.8s cubic-bezier(0.2, 0.65, 0.25, 1);
  }
  .chapter__inner.is-visible { opacity: 1; transform: none; }
}

/* ---------- responsive ---------- */
@media (max-width: 760px) {
  .cols, .lab__explain { grid-template-columns: 1fr; gap: 1.4rem; }
  .facts { grid-template-columns: 1fr; }
  .lab__grid { grid-template-columns: 1fr; }
  .lab__console { order: 2; display: grid; grid-template-columns: 1fr 1fr; }
  .lab__note { grid-column: 1 / -1; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .hero__cta-arrow { animation: none; }
  .chapter__inner { opacity: 1; transform: none; }
}