:root {
  --bg: #0e0e10;
  --mono: 'IBM Plex Mono', ui-monospace, monospace;
  --sans: 'Instrument Sans', system-ui, sans-serif;
  --sticky-top: 3.5rem;
  --layer-offset: 2.75rem;
}

* { box-sizing: border-box; margin: 0; padding: 0; }

html { scroll-behavior: smooth; }

body {
  font-family: var(--sans);
  background: var(--bg);
  color: #e8e6e3;
  line-height: 1.55;
  overflow-x: hidden;
}

.nav {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  z-index: 100;
  display: flex;
  justify-content: space-between;
  padding: 1rem 1.5rem;
  font-family: var(--mono);
  font-size: 0.72rem;
  background: rgba(14, 14, 16, 0.85);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid rgba(255, 255, 255, 0.06);
}

.nav a {
  color: #6b6966;
  text-decoration: none;
}

.nav a:hover { color: #c4a574; }

.depth {
  color: #6b6966;
  font-variant-numeric: tabular-nums;
}

.stack-viewport {
  padding: 0 1.5rem 8rem;
  max-width: 640px;
  margin: 0 auto;
}

/* Sticky card stack — each layer sticks, next slides over */
.layer {
  position: sticky;
  min-height: 72vh;
  margin-bottom: 1.5rem;
  border-radius: 12px;
  border: 1px solid rgba(255, 255, 255, 0.08);
  box-shadow:
    0 -1px 0 rgba(255, 255, 255, 0.05) inset,
    0 24px 48px rgba(0, 0, 0, 0.45),
    0 4px 12px rgba(0, 0, 0, 0.3);
  transform-origin: center top;
  transition: transform 0.15s ease-out;
}

.layer-0 { top: var(--sticky-top); z-index: 1; background: #1a1a1e; }
.layer-1 { top: calc(var(--sticky-top) + var(--layer-offset) * 1); z-index: 2; background: #222228; }
.layer-2 { top: calc(var(--sticky-top) + var(--layer-offset) * 2); z-index: 3; background: #2a2a32; }
.layer-3 { top: calc(var(--sticky-top) + var(--layer-offset) * 3); z-index: 4; background: #32323c; }
.layer-4 { top: calc(var(--sticky-top) + var(--layer-offset) * 4); z-index: 5; background: #3a3a46; }
.layer-5 { top: calc(var(--sticky-top) + var(--layer-offset) * 5); z-index: 6; background: #42424e; }
.layer-6 { top: calc(var(--sticky-top) + var(--layer-offset) * 6); z-index: 7; background: #4a4a58; margin-bottom: 4rem; }

.layer-inner {
  padding: 2rem 2rem 2.5rem;
}

.layer-head {
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem 1rem;
  margin-bottom: 1.25rem;
  padding-bottom: 0.75rem;
  border-bottom: 1px solid rgba(255, 255, 255, 0.08);
  font-family: var(--mono);
  font-size: 0.7rem;
}

.layer-id {
  color: #c4a574;
  font-weight: 600;
  letter-spacing: 0.08em;
}

.layer-name {
  color: #6b6966;
  text-transform: uppercase;
  letter-spacing: 0.12em;
}

.layer-link {
  margin-left: auto;
  color: #8b9cb3;
  text-decoration: none;
  font-size: 0.65rem;
}

.layer-link:hover { color: #c4a574; }

.layer h1 {
  font-size: clamp(2.5rem, 10vw, 3.5rem);
  font-weight: 600;
  letter-spacing: -0.04em;
  margin-bottom: 0.35rem;
}

.layer h2 {
  font-size: 1.75rem;
  font-weight: 600;
  letter-spacing: -0.03em;
  margin-bottom: 0.5rem;
}

.tagline {
  font-family: var(--mono);
  font-size: 0.8rem;
  color: #6b6966;
  letter-spacing: 0.06em;
  margin-bottom: 1rem;
}

.body {
  color: #a8a6a1;
  font-size: 1rem;
  max-width: 38ch;
  margin-bottom: 1rem;
}

.chips {
  display: flex;
  flex-wrap: wrap;
  gap: 0.5rem;
  margin-bottom: 1rem;
}

.chips span {
  font-family: var(--mono);
  font-size: 0.65rem;
  padding: 0.3rem 0.55rem;
  background: rgba(196, 165, 116, 0.12);
  color: #c4a574;
  border: 1px solid rgba(196, 165, 116, 0.25);
  border-radius: 4px;
}

.avail {
  font-family: var(--mono);
  font-size: 0.72rem;
  color: #7eb87a;
  letter-spacing: 0.04em;
}

.stack-list {
  list-style: none;
  font-family: var(--mono);
  font-size: 0.78rem;
  color: #6b6966;
  line-height: 1.7;
}

.contact-row {
  display: flex;
  flex-wrap: wrap;
  gap: 0.75rem;
  margin: 1.25rem 0;
}

.btn {
  font-family: var(--mono);
  font-size: 0.8rem;
  padding: 0.65rem 1.1rem;
  background: #c4a574;
  color: #0e0e10;
  text-decoration: none;
  font-weight: 600;
  border-radius: 6px;
  transition: background 0.15s, color 0.15s;
}

.btn:hover {
  background: #e8d4b0;
}

.btn-ghost {
  background: transparent;
  color: #c4a574;
  border: 1px solid rgba(196, 165, 116, 0.4);
}

.btn-ghost:hover {
  background: rgba(196, 165, 116, 0.1);
  color: #e8d4b0;
}

.guarantees {
  font-family: var(--mono);
  font-size: 0.68rem;
  color: #6b6966;
  letter-spacing: 0.02em;
}

.layer-foot {
  display: flex;
  justify-content: space-between;
  margin-top: 2rem;
  padding-top: 1rem;
  border-top: 1px solid rgba(255, 255, 255, 0.08);
  font-family: var(--mono);
  font-size: 0.65rem;
  color: #6b6966;
}

.layer-foot a {
  color: #6b6966;
  text-decoration: none;
}

.layer-foot a:hover { color: #c4a574; }

/* Side ruler — stack depth indicator */
.stack-ruler {
  position: fixed;
  right: 1.25rem;
  top: 50%;
  transform: translateY(-50%);
  z-index: 50;
  display: flex;
  flex-direction: column;
  gap: 0.35rem;
  font-family: var(--mono);
  font-size: 0.55rem;
  color: #3a3a40;
  letter-spacing: 0.06em;
  pointer-events: none;
}

.stack-ruler span {
  padding: 0.15rem 0;
  transition: color 0.2s, transform 0.2s;
}

.stack-ruler span.active {
  color: #c4a574;
  transform: translateX(-4px);
}

@media (max-width: 700px) {
  .stack-ruler { display: none; }
  :root { --layer-offset: 1.75rem; }
  .layer { min-height: 65vh; }
  .layer-inner { padding: 1.5rem 1.25rem 2rem; }
}

/* Subtle edge highlight — “card” lip */
.layer::before {
  content: '';
  position: absolute;
  top: 0;
  left: 0;
  right: 0;
  height: 3px;
  border-radius: 12px 12px 0 0;
  background: linear-gradient(90deg, transparent, rgba(255, 255, 255, 0.12), transparent);
  pointer-events: none;
}