:root {
  --color-parchment: #f4ece1;
  --color-linen: #ede3d5;
  --color-umber: #2c1e10;
  --color-terracotta: #c45a3c;
  --color-copper: #7a6e52;
  --color-shadow: #b8a68e;
  --color-ochre: #d4a44a;
  --color-sienna: #8b5a38;
  --font-display: "Libre Baskerville", Georgia, serif;
  --font-body: "Source Serif 4", Georgia, serif;
  --font-label: "DM Sans", Arial, sans-serif;
  --ease: cubic-bezier(0.4, 0, 0.2, 1);
}

/* Design terms: IntersectionObserver triggers border-draw animation when each `.iso-panel` enters viewport (threshold: 0.15). Triple serif notes: Source Serif 4 as display and body serifs (with DM Sans reserved only for captions; Source Serif 4" (Google Fonts. */

@keyframes border-draw-reference {
  from { stroke-dashoffset: 1; }
  to { stroke-dashoffset: 0; }
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  color: var(--color-umber);
  background: var(--color-parchment);
  font-family: var(--font-body);
  font-size: clamp(1rem, 1.2vw, 1.15rem);
  line-height: 1.72;
  letter-spacing: 0.005em;
  overflow-x: hidden;
}

body::before {
  content: "";
  position: fixed;
  inset: 0;
  pointer-events: none;
  background-image: linear-gradient(90deg, rgba(139, 90, 56, 0.045) 1px, transparent 1px), linear-gradient(rgba(139, 90, 56, 0.035) 1px, transparent 1px);
  background-size: 56px 56px;
  transform: rotate(45deg) scale(1.45);
  transform-origin: center;
  opacity: 0.45;
  z-index: 0;
}

#particles {
  position: fixed;
  inset: 0;
  width: 100%;
  height: 100%;
  z-index: 1;
  pointer-events: none;
}

.noise-overlay {
  position: fixed;
  inset: 0;
  pointer-events: none;
  z-index: 4;
  opacity: 0.04;
  background-image: url("data:image/svg+xml,%3Csvg xmlns='http://www.w3.org/2000/svg' width='220' height='220'%3E%3Cfilter id='n'%3E%3CfeTurbulence type='fractalNoise' baseFrequency='0.65' numOctaves='4' stitchTiles='stitch'/%3E%3CfeColorMatrix type='matrix' values='0.75 0 0 0 0.55 0 0.48 0 0 0.32 0 0 0.25 0 0.12 0 0 0 1 0'/%3E%3C/filter%3E%3Crect width='100%25' height='100%25' filter='url(%23n)'/%3E%3C/svg%3E");
}

main, .iso-tabs { position: relative; z-index: 2; }

.iso-tabs {
  position: fixed;
  top: 24px;
  right: 24px;
  display: flex;
  gap: 10px;
  z-index: 8;
}

.iso-tab {
  color: var(--color-linen);
  background: var(--color-copper);
  font-family: var(--font-label);
  font-size: 0.75rem;
  font-weight: 500;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  text-decoration: none;
  padding: 0.65rem 0.9rem;
  transform: skewX(-18deg) rotate(-2deg);
  box-shadow: 5px 5px 0 rgba(139, 90, 56, 0.18);
  transition: background 260ms var(--ease), transform 260ms var(--ease), box-shadow 260ms var(--ease);
}

.iso-tab:hover {
  background: var(--color-terracotta);
  transform: skewX(-18deg) rotate(-2deg) translate(-2px, -2px);
  box-shadow: 8px 8px 0 rgba(139, 90, 56, 0.22);
}

.hero {
  min-height: 100vh;
  display: grid;
  place-items: center;
  padding: 7rem clamp(1rem, 4vw, 5rem) 4rem;
  perspective: 1200px;
  position: relative;
}

.iso-book {
  position: absolute;
  width: min(74vw, 780px);
  height: min(45vw, 420px);
  transform: rotateX(58deg) rotateZ(-28deg);
  background: var(--color-linen);
  box-shadow: 24px 24px 0 rgba(184, 166, 142, 0.45), inset 0 0 0 2px rgba(139, 90, 56, 0.18);
  opacity: 0.62;
}

.iso-book::before, .iso-book::after {
  content: "";
  position: absolute;
  top: 0;
  bottom: 0;
  width: 50%;
  border: 1px solid rgba(139, 90, 56, 0.18);
}

.iso-book::before { left: 0; background: rgba(212, 164, 74, 0.12); }
.iso-book::after { right: 0; background: rgba(196, 90, 60, 0.08); }
.iso-book span { position: absolute; left: 50%; top: 0; bottom: 0; width: 7px; background: rgba(139, 90, 56, 0.22); }

.iso-panel {
  position: relative;
  background: var(--color-linen);
  min-height: 220px;
  padding: clamp(1.25rem, 2.3vw, 2rem);
  box-shadow: 8px 8px 0 rgba(139, 90, 56, 0.15), 0 18px 44px rgba(44, 30, 16, 0.08);
  transform: rotateX(2deg) rotateY(-2deg);
  transform-style: preserve-3d;
  transition: transform 320ms var(--ease), box-shadow 320ms var(--ease);
  overflow: hidden;
}

.iso-panel::before {
  content: "";
  position: absolute;
  inset: 0;
  background: repeating-linear-gradient(135deg, rgba(244, 236, 225, 0.28) 0 2px, transparent 2px 9px);
  opacity: 0.42;
  pointer-events: none;
}

.iso-panel.is-hovered {
  box-shadow: 14px 14px 0 rgba(139, 90, 56, 0.20), 0 26px 54px rgba(44, 30, 16, 0.11);
}

.iso-panel--hero {
  width: min(1040px, 92vw);
  min-height: 64vh;
  display: grid;
  place-items: center;
  text-align: center;
  padding: clamp(2rem, 6vw, 5.5rem);
  transform: rotateX(4deg) rotateY(-3deg);
}

.panel-border {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  pointer-events: none;
  z-index: 2;
}

.panel-border rect {
  fill: none;
  stroke: var(--color-sienna);
  stroke-width: 1.5px;
  vector-effect: non-scaling-stroke;
  stroke-dasharray: 1;
  stroke-dashoffset: 1;
  transition: stroke-dashoffset 1200ms var(--ease);
}

.iso-panel.is-drawn .panel-border rect { stroke-dashoffset: 0; }

.panel-content {
  position: relative;
  z-index: 3;
  opacity: 0;
  transition: opacity 600ms var(--ease) 650ms;
}

.iso-panel.is-drawn .panel-content { opacity: 1; }

h1, h2, h3 {
  margin: 0;
  font-family: var(--font-display);
  font-weight: 700;
  line-height: 1.25;
  letter-spacing: 0.01em;
  color: var(--color-umber);
}

h1 { font-size: clamp(2.4rem, 5.5vw, 4.8rem); }
h2 { font-size: clamp(1.6rem, 3vw, 2.8rem); }
h3 { font-size: clamp(1.25rem, 1.9vw, 1.75rem); margin-bottom: 0.65rem; }
p { margin: 0; }

.subtitle {
  max-width: 690px;
  margin: 1.2rem auto 0;
  font-size: clamp(1.15rem, 1.8vw, 1.55rem);
}

.eyebrow, .panel-label, .step-number, .hero-notes, .colophon-lines {
  font-family: var(--font-label);
  font-size: 0.75rem;
  text-transform: uppercase;
  letter-spacing: 0.12em;
  color: var(--color-copper);
}

.hero-notes {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  gap: 0.8rem 1.3rem;
  margin-top: 2rem;
}

.section-block {
  width: min(1180px, 92vw);
  margin: 0 auto;
  padding: 5rem 0;
}

.section-heading {
  max-width: 780px;
  margin-bottom: 2rem;
}

.iso-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(280px, 1fr));
  grid-auto-rows: minmax(200px, auto);
  gap: 12px;
  perspective: 1100px;
}

.iso-panel--2x1 { grid-column: span 2; }
.iso-panel--1x2 { grid-row: span 2; }

.panel-label { color: var(--color-terracotta); margin-bottom: 0.75rem; }

.cube-list {
  list-style: none;
  padding: 0;
  margin: 1.3rem 0 0;
}

.cube-list li {
  display: flex;
  align-items: center;
  gap: 0.8rem;
  margin: 0.55rem 0;
  font-family: var(--font-label);
  font-size: 0.78rem;
  text-transform: uppercase;
  letter-spacing: 0.12em;
}

.iso-cube {
  position: relative;
  width: 16px;
  height: 16px;
  display: inline-block;
  background: var(--color-terracotta);
  transform: rotate(45deg) skew(-12deg, -12deg);
}

.iso-cube::before, .iso-cube::after {
  content: "";
  position: absolute;
  background: var(--color-ochre);
}

.iso-cube::before { width: 16px; height: 7px; left: -4px; top: -7px; transform: skew(45deg); background: var(--color-sienna); }
.iso-cube::after { width: 7px; height: 16px; right: -7px; top: -4px; transform: skewY(45deg); background: var(--color-ochre); }

.iso-beam {
  width: 88vw;
  height: 22px;
  margin: 1rem auto 0;
  background: var(--color-copper);
  transform: skewX(-32deg) rotate(-2deg);
  box-shadow: 10px 10px 0 rgba(139, 90, 56, 0.14);
}

.iso-beam--right { transform: skewX(32deg) rotate(2deg); }

.iso-conveyor {
  display: grid;
  grid-template-columns: repeat(5, minmax(180px, 1fr));
  gap: 14px;
  perspective: 1000px;
}

.iso-step {
  min-height: 230px;
  padding: 1.35rem;
  background: var(--color-linen);
  border: 1.5px solid var(--color-sienna);
  box-shadow: 8px 8px 0 rgba(139, 90, 56, 0.15);
  transform: rotateX(9deg) rotateY(-5deg);
  transition: transform 320ms var(--ease), box-shadow 320ms var(--ease);
}

.iso-step:hover {
  transform: rotateX(6deg) rotateY(-2deg) translateY(-6px);
  box-shadow: 13px 13px 0 rgba(139, 90, 56, 0.20);
}

.step-number { display: block; color: var(--color-terracotta); margin-bottom: 1rem; }

.colophon {
  min-height: 80vh;
  display: grid;
  place-items: center;
  padding: 6rem 1rem;
  perspective: 1200px;
}

.iso-panel--colophon {
  width: min(760px, 92vw);
  min-height: 390px;
  display: grid;
  place-items: center;
  text-align: center;
  box-shadow: 18px 24px 0 rgba(139, 90, 56, 0.22), 0 36px 70px rgba(44, 30, 16, 0.12);
}

.iso-panel--colophon p:not(.eyebrow) { margin-top: 1rem; }

.colophon-lines {
  display: grid;
  gap: 0.6rem;
  margin-top: 1.8rem;
  color: var(--color-sienna);
}

@media (max-width: 900px) {
  .iso-panel--2x1, .iso-panel--1x2 { grid-column: auto; grid-row: auto; }
  .iso-conveyor { grid-template-columns: 1fr 1fr; }
  .iso-tabs { right: 12px; top: 12px; gap: 6px; }
  .iso-tab { padding: 0.55rem 0.65rem; }
}

@media (max-width: 560px) {
  .iso-conveyor { grid-template-columns: 1fr; }
  .hero { padding-top: 6rem; }
  .iso-panel--hero { min-height: 58vh; }
  .iso-tabs { transform: scale(0.86); transform-origin: top right; }
}