:root {
  /* Interface labels and coordinates:** coordinates* `Space Grotesk` from Google Fonts */
  --slate: #151A1F;
  --panel: #232A30;
  --mist: #D7D9D2;
  --sage: #8FAE9A;
  --cyan: #7FA9B8;
  --amber: #D6A85F;
  --clay: #B97862;
  --grid: #394149;
  --soft: rgba(215, 217, 210, 0.68);
  --radius-xl: 34px;
  --radius-lg: 26px;
  --radius-sm: 18px;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--slate);
  color: var(--mist);
  font-family: "Manrope", sans-serif;
  overflow-x: hidden;
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  background:
    radial-gradient(circle at 18% 12%, rgba(214, 168, 95, 0.16), transparent 31%),
    radial-gradient(circle at 86% 32%, rgba(127, 169, 184, 0.13), transparent 34%),
    radial-gradient(circle at 45% 84%, rgba(143, 174, 154, 0.09), transparent 36%),
    linear-gradient(180deg, rgba(21, 26, 31, 0.2), rgba(21, 26, 31, 0.92));
  z-index: -3;
}

body::after {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  opacity: .18;
  background-image: repeating-radial-gradient(circle at 20% 10%, rgba(215, 217, 210, .16) 0 1px, transparent 1px 4px);
  mix-blend-mode: overlay;
  z-index: -1;
}

.ambient-grid {
  position: fixed;
  left: -12vw;
  right: -12vw;
  bottom: -18vh;
  height: 64vh;
  background-image:
    linear-gradient(rgba(57, 65, 73, .62) 1px, transparent 1px),
    linear-gradient(90deg, rgba(57, 65, 73, .62) 1px, transparent 1px);
  background-size: 54px 54px;
  transform: perspective(620px) rotateX(64deg);
  transform-origin: bottom;
  opacity: .32;
  pointer-events: none;
  z-index: -2;
}

.chapter-rail {
  position: fixed;
  z-index: 20;
  top: 50%;
  left: 24px;
  transform: translateY(-50%);
  display: flex;
  flex-direction: column;
  gap: 10px;
  padding: 12px;
  border: 1px solid rgba(57, 65, 73, .8);
  border-radius: 999px;
  background: rgba(35, 42, 48, .72);
  backdrop-filter: blur(18px);
  box-shadow: inset 0 0 24px rgba(21, 26, 31, .8);
}

.chapter-rail a {
  color: rgba(215, 217, 210, .54);
  text-decoration: none;
  font-family: "Space Grotesk", sans-serif;
  font-size: 11px;
  writing-mode: vertical-rl;
  letter-spacing: .08em;
  text-transform: uppercase;
  padding: 10px 6px;
  border-radius: 999px;
  transition: color .3s ease, background .3s ease;
}

.chapter-rail a.active,
.chapter-rail a:hover { color: var(--slate); background: var(--cyan); }

.chapter {
  min-height: 100vh;
  display: grid;
  place-items: center;
  padding: 7vh 6vw 7vh 92px;
  position: relative;
}

.chapter-shell { width: min(1180px, 100%); }

.bento-board {
  display: grid;
  gap: 16px;
  transform-style: preserve-3d;
}

.bento-cell {
  position: relative;
  overflow: hidden;
  border: 1px solid rgba(57, 65, 73, .82);
  border-radius: var(--radius-lg);
  background:
    linear-gradient(145deg, rgba(35, 42, 48, .98), rgba(27, 33, 38, .96)),
    var(--panel);
  box-shadow:
    inset 0 1px 0 rgba(215, 217, 210, .06),
    inset 0 0 46px rgba(21, 26, 31, .5),
    0 28px 70px rgba(0, 0, 0, .28);
}

.bento-cell::before {
  content: "";
  position: absolute;
  inset: 0;
  background-image:
    linear-gradient(rgba(57, 65, 73, .18) 1px, transparent 1px),
    linear-gradient(90deg, rgba(57, 65, 73, .16) 1px, transparent 1px);
  background-size: 32px 32px;
  mask-image: linear-gradient(135deg, black, transparent 72%);
  pointer-events: none;
}

.opening-board {
  min-height: 82vh;
  grid-template-columns: 1.25fr .72fr .48fr;
  grid-template-rows: .9fr .62fr .72fr;
  grid-template-areas:
    "hero hero title"
    "hero hero controls"
    "caption tray controls";
}

.hero-cell { grid-area: hero; border-radius: var(--radius-xl); min-height: 520px; }
.title-cell { grid-area: title; padding: 30px; }
.controls-cell { grid-area: controls; padding: 24px; }
.tray-cell { grid-area: tray; padding: 22px; }
.caption-cell { grid-area: caption; padding: 26px; }

.cell-tag,
.eyebrow,
.timecode,
.coordinate-label,
.coordinate-grid,
.film-frame b,
.quiet-controls span {
  font-family: "Space Grotesk", sans-serif;
  text-transform: uppercase;
  letter-spacing: .08em;
}

.cell-tag {
  position: relative;
  z-index: 2;
  color: var(--cyan);
  font-size: 11px;
  margin: 22px 22px 0;
}

.eyebrow { color: var(--amber); font-size: 12px; margin: 0 0 18px; }

h1, h2, h3 {
  font-family: "Nunito Sans", sans-serif;
  letter-spacing: -0.04em;
  margin: 0;
}

h1 { font-size: clamp(48px, 8vw, 92px); line-height: .92; }
h2 { font-size: clamp(38px, 6vw, 72px); line-height: .92; }
h3 { font-size: clamp(24px, 3vw, 36px); line-height: .96; }
p { color: var(--soft); line-height: 1.65; }

.grid-floor {
  position: absolute;
  inset: 68px 34px 34px;
  border-radius: 28px;
  background:
    linear-gradient(rgba(57, 65, 73, .52) 1px, transparent 1px),
    linear-gradient(90deg, rgba(57, 65, 73, .48) 1px, transparent 1px),
    radial-gradient(circle at 72% 24%, rgba(127, 169, 184, .18), transparent 28%),
    radial-gradient(circle at 26% 76%, rgba(214, 168, 95, .13), transparent 34%);
  background-size: 46px 46px, 46px 46px, auto, auto;
  transform: perspective(800px) rotateX(54deg) rotateZ(-7deg);
  transform-origin: center;
  box-shadow: inset 0 0 80px rgba(21, 26, 31, .9);
}

.route {
  position: absolute;
  height: 6px;
  border-radius: 999px;
  background: linear-gradient(90deg, transparent, var(--sage), var(--cyan), transparent);
  opacity: .75;
}

.route-a { width: 62%; left: 16%; top: 44%; transform: rotate(-8deg); }
.route-b { width: 44%; left: 30%; top: 62%; transform: rotate(22deg); background: linear-gradient(90deg, transparent, var(--amber), var(--clay), transparent); }

.iso-block,
.iso-gate,
.iso-agent,
.ghost-trail,
.state-agent,
.frame-agent,
.robot-agent,
.path-dot {
  position: absolute;
  transform-style: preserve-3d;
}

.iso-block {
  width: 54px;
  height: 54px;
  background: linear-gradient(145deg, rgba(127, 169, 184, .88), rgba(57, 65, 73, .92));
  transform: rotate(45deg) skew(-8deg, -8deg);
  border-radius: 8px;
  box-shadow: 12px 14px 0 rgba(21, 26, 31, .36);
}

.block-one { left: 18%; top: 24%; }
.block-two { left: 54%; top: 34%; background: linear-gradient(145deg, rgba(143, 174, 154, .9), rgba(57, 65, 73, .94)); }
.block-three { left: 66%; top: 66%; background: linear-gradient(145deg, rgba(214, 168, 95, .84), rgba(57, 65, 73, .94)); }

.iso-gate {
  left: 42%; top: 55%;
  width: 58px; height: 38px;
  display: grid; place-items: center;
  border: 1px solid var(--amber);
  color: var(--amber);
  border-radius: 12px;
  font-family: "Space Grotesk", sans-serif;
  background: rgba(21, 26, 31, .76);
}

.iso-agent {
  width: 24px; height: 24px;
  border-radius: 50%;
  background: var(--sage);
  box-shadow: 0 0 0 8px rgba(143, 174, 154, .1), 0 0 24px rgba(143, 174, 154, .48);
  animation: agentDrift 7s ease-in-out infinite;
}

.iso-agent span {
  position: absolute;
  inset: 6px;
  border-radius: 50%;
  background: var(--mist);
}

.agent-a { left: 20%; top: 48%; }
.agent-b { left: 52%; top: 42%; animation-delay: -2s; background: var(--cyan); }
.agent-c { left: 68%; top: 58%; animation-delay: -4s; background: var(--clay); }

.ghost-trail {
  width: 70px; height: 18px;
  border-radius: 999px;
  background: linear-gradient(90deg, transparent, rgba(215, 217, 210, .25));
  filter: blur(.2px);
}
.trail-one { left: 25%; top: 52%; }
.trail-two { left: 57%; top: 48%; transform: rotate(12deg); }

.focus-ring {
  position: absolute;
  border: 2px solid var(--cyan);
  border-radius: 50%;
  box-shadow: 0 0 0 10px rgba(127, 169, 184, .08), 0 0 44px rgba(127, 169, 184, .24);
  pointer-events: none;
}

.hero-focus { width: 150px; height: 150px; left: 48%; top: 34%; animation: focusPull 6s ease-in-out infinite; }
.instructor-note {
  position: absolute;
  right: 34px; bottom: 28px;
  padding: 10px 14px;
  border: 1px solid rgba(214, 168, 95, .5);
  border-radius: 999px;
  color: var(--amber);
  background: rgba(21, 26, 31, .65);
  font-family: "Space Grotesk", sans-serif;
  font-size: 12px;
}

.control-row { display: flex; flex-wrap: wrap; gap: 8px; margin-top: 22px; }
.sim-control {
  border: 1px solid var(--grid);
  color: var(--mist);
  background: rgba(21, 26, 31, .52);
  padding: 10px 13px;
  border-radius: 999px;
  font-family: "Space Grotesk", sans-serif;
  text-transform: uppercase;
  cursor: pointer;
}
.sim-control.active { background: var(--amber); color: var(--slate); border-color: var(--amber); }
.timeline-meter { height: 8px; border-radius: 999px; background: rgba(57, 65, 73, .8); margin: 24px 0; overflow: hidden; }
.timeline-meter span { display: block; height: 100%; width: 18%; background: linear-gradient(90deg, var(--amber), var(--cyan)); border-radius: inherit; transition: width .55s ease; }

.object-tray { display: grid; grid-template-columns: repeat(4, 1fr); gap: 12px; margin: 22px 0; }
.object-tray span { height: 48px; border-radius: 14px; background: rgba(21, 26, 31, .45); border: 1px solid var(--grid); position: relative; }
.mini-cube::after { content: ""; position: absolute; inset: 13px; background: var(--cyan); transform: rotate(45deg); border-radius: 4px; }
.mini-sensor::after { content: ""; position: absolute; inset: 12px; border: 2px solid var(--sage); border-radius: 50%; }
.mini-gate::after { content: "if"; position: absolute; inset: 10px; display: grid; place-items: center; color: var(--amber); font-family: "Space Grotesk"; }
.mini-agent::after { content: ""; position: absolute; width: 16px; height: 16px; left: 16px; top: 16px; background: var(--clay); border-radius: 50%; }
.timecode { color: var(--amber); font-size: 12px; }

.lesson-header { margin-bottom: 28px; }
.split-header { display: grid; grid-template-columns: 1.2fr .8fr; gap: 28px; align-items: end; }

.lens-board { grid-template-columns: 1fr 330px; grid-template-rows: 390px 230px; grid-template-areas: "main params" "main caption"; }
.lens-main { grid-area: main; border-radius: var(--radius-xl); }
.parameter-panel { grid-area: params; padding: 22px; }
.lens-caption { grid-area: caption; padding: 26px; }
.loop-diagram { position: absolute; inset: 70px 50px 45px; }
.loop-node {
  position: absolute; width: 126px; height: 78px; border-radius: 22px;
  display: grid; place-items: center;
  border: 1px solid var(--grid);
  background: rgba(21, 26, 31, .55);
  font-family: "Space Grotesk"; color: var(--mist);
}
.input-node { left: 6%; top: 38%; color: var(--cyan); }
.memory-node { left: 38%; top: 8%; color: var(--sage); }
.rule-node { right: 12%; top: 38%; color: var(--amber); }
.action-node { left: 38%; bottom: 7%; color: var(--clay); }
.loop-path { position: absolute; inset: 34px 74px; border: 2px dashed rgba(127, 169, 184, .44); border-radius: 50%; animation: loopSpin 18s linear infinite; }
.lens-focus { width: 190px; height: 190px; right: 12%; top: 28%; }
.bead-track { min-height: 230px; position: relative; border-left: 1px solid var(--grid); margin-left: 22px; }
.parameter-bead { position: absolute; left: -14px; padding: 8px 12px; border-radius: 999px; background: var(--panel); border: 1px solid var(--grid); color: var(--mist); font-family: "Space Grotesk"; font-size: 12px; animation: beadSlide 7s ease-in-out infinite; }
.bead-delay { top: 8%; color: var(--amber); }
.bead-memory { top: 28%; color: var(--sage); animation-delay: -1s; }
.bead-noise { top: 48%; color: var(--clay); animation-delay: -2s; }
.bead-reward { top: 68%; color: var(--cyan); animation-delay: -3s; }
.bead-constraint { top: 86%; color: var(--mist); animation-delay: -4s; }

.cause-board { grid-template-columns: repeat(3, 1fr); grid-template-rows: 300px 240px; }
.cause-board .bento-cell { padding: 24px; }
.annotation-panel { grid-column: span 2; }
.magnify-panel { padding: 0 !important; }
.mini-stage { position: relative; height: 130px; border-radius: 20px; margin: 20px 0; background: linear-gradient(rgba(57, 65, 73, .5) 1px, transparent 1px), linear-gradient(90deg, rgba(57, 65, 73, .5) 1px, transparent 1px); background-size: 28px 28px; }
.state-agent { width: 24px; height: 24px; border-radius: 50%; top: 52%; box-shadow: 0 0 0 10px rgba(215, 217, 210, .05); }
.state-agent:nth-child(1) { left: 20%; }.state-agent:nth-child(2) { left: 46%; }.state-agent:nth-child(3) { left: 72%; }
.sage { background: var(--sage); }.cyan { background: var(--cyan); }.clay { background: var(--clay); }
.disrupted .state-agent:nth-child(1) { top: 36%; }.disrupted .state-agent:nth-child(3) { top: 68%; }
.leader-line { position: absolute; left: 23%; right: 20%; top: 63%; border-top: 1px solid var(--sage); opacity: .5; }
.change-dial { width: 138px; height: 138px; border-radius: 50%; border: 1px solid var(--grid); margin: 26px auto; background: conic-gradient(var(--clay) 0 72deg, rgba(57,65,73,.7) 72deg); position: relative; }
.change-dial span { position: absolute; inset: 32px; border-radius: 50%; background: var(--panel); box-shadow: inset 0 0 20px rgba(21, 26, 31, .7); }
.small-focus { width: 92px; height: 92px; left: 54%; top: 34%; }
.annotation-arrow { font-size: 62px; color: var(--amber); }
.magnifier-view { position: absolute; inset: 24px; border-radius: 28px; border: 2px solid var(--cyan); background: radial-gradient(circle, rgba(127,169,184,.18), transparent 60%), var(--panel); display: grid; place-items: center; }
.magnified-agent { width: 90px; height: 90px; background: var(--clay); border-radius: 50%; box-shadow: 0 0 0 28px rgba(185, 120, 98, .1); }
.coordinate-label { position: absolute; bottom: 24px; color: var(--cyan); font-size: 12px; }

.film-stack { display: grid; gap: 16px; }
.film-frame { min-height: 132px; padding: 26px 34px 26px 140px; display: grid; align-content: center; transform: scale(.96); opacity: .62; transition: transform .45s ease, opacity .45s ease, border-color .45s ease; }
.film-frame.active { transform: scale(1); opacity: 1; border-color: var(--amber); }
.film-frame::after { content: attr(data-frame); position: absolute; right: 28px; top: 24px; color: var(--amber); font-family: "Space Grotesk"; }
.frame-agent { width: 34px; height: 34px; left: 54px; top: 49px; border-radius: 50%; background: var(--sage); box-shadow: -24px 0 0 rgba(143,174,154,.16), -48px 0 0 rgba(143,174,154,.08); }
.frame-agent.cyan { background: var(--cyan); }.frame-agent.clay { background: var(--clay); }
.film-frame p { margin: 6px 0 0; }

.sandbox-board { grid-template-columns: 1.2fr .58fr; grid-template-rows: 460px 220px; grid-template-areas: "stage caption" "stage coords"; }
.sandbox-stage { grid-area: stage; border-radius: var(--radius-xl); }
.final-caption { grid-area: caption; padding: 30px; }
.coordinate-cell { grid-area: coords; padding: 24px; }
.robot-floor { inset: 76px 42px 42px; }
.robot-agent { width: 44px; height: 44px; border-radius: 14px; background: var(--cyan); left: 18%; top: 56%; box-shadow: 0 0 0 12px rgba(127,169,184,.1); animation: robotPath 8s ease-in-out infinite; }
.path-dot { width: 13px; height: 13px; background: var(--amber); border-radius: 50%; }
.dot-one { left: 30%; top: 50%; }.dot-two { left: 52%; top: 38%; }.dot-three { left: 72%; top: 52%; }
.sandbox-tile { position: absolute; padding: 9px 12px; border-radius: 14px; background: rgba(21,26,31,.76); border: 1px solid var(--grid); font-family: "Space Grotesk"; color: var(--mist); }
.tile-delay { left: 20%; top: 22%; color: var(--amber); }.tile-reward { left: 54%; top: 24%; color: var(--sage); }.tile-limit { right: 12%; bottom: 24%; color: var(--clay); }
.quiet-controls { display: flex; gap: 10px; margin-top: 20px; }
.quiet-controls span { border: 1px solid var(--grid); border-radius: 999px; padding: 8px 11px; color: var(--cyan); font-size: 11px; }
.coordinate-grid { display: grid; gap: 12px; color: var(--soft); font-size: 12px; }
.coordinate-grid span { padding-bottom: 12px; border-bottom: 1px solid var(--grid); }

.chapter.in-view .bento-board { animation: boardArrive .9s ease both; }
.chapter.in-view .lesson-header { animation: captionFade .8s ease both; }

@keyframes agentDrift { 0%,100% { transform: translate(0,0); } 45% { transform: translate(62px,-22px); } 70% { transform: translate(98px,18px); } }
@keyframes focusPull { 0%,100% { transform: scale(1.18); opacity: .5; } 46% { transform: scale(.72); opacity: 1; } }
@keyframes loopSpin { to { transform: rotate(360deg); } }
@keyframes beadSlide { 0%,100% { transform: translateX(0); } 50% { transform: translateX(95px); } }
@keyframes robotPath { 0%,100% { transform: translate(0,0) rotate(0deg); } 35% { transform: translate(170px,-54px) rotate(12deg); } 70% { transform: translate(340px,6px) rotate(-8deg); } }
@keyframes boardArrive { from { opacity: .45; transform: scale(.965); filter: blur(2px); } to { opacity: 1; transform: scale(1); filter: blur(0); } }
@keyframes captionFade { from { opacity: 0; transform: translateY(18px); } to { opacity: 1; transform: translateY(0); } }

@media (max-width: 920px) {
  .chapter { padding: 80px 20px; }
  .chapter-rail { display: none; }
  .opening-board, .lens-board, .cause-board, .sandbox-board { display: flex; flex-direction: column; }
  .hero-cell, .lens-main, .sandbox-stage { min-height: 520px; }
  .split-header { grid-template-columns: 1fr; }
  .film-frame { padding-left: 96px; }
}

@media (max-width: 560px) {
  h1 { font-size: 48px; }
  h2 { font-size: 40px; }
  .grid-floor { left: 18px; right: 18px; }
  .object-tray { grid-template-columns: repeat(2, 1fr); }
}