@font-face {
  font-family: "Source Serif 4";
  src: url("fonts/source-serif-4-400.woff2") format("woff2");
  font-weight: 400;
  font-style: normal;
  font-display: swap;
}
@font-face {
  font-family: "Source Serif 4";
  src: url("fonts/source-serif-4-600.woff2") format("woff2");
  font-weight: 600;
  font-style: normal;
  font-display: swap;
}
@font-face {
  font-family: "Source Serif 4";
  src: url("fonts/source-serif-4-400-italic.woff2") format("woff2");
  font-weight: 400;
  font-style: italic;
  font-display: swap;
}
@font-face {
  font-family: "Source Sans 3";
  src: url("fonts/source-sans-3-400.woff2") format("woff2");
  font-weight: 400;
  font-style: normal;
  font-display: swap;
}
@font-face {
  font-family: "Source Sans 3";
  src: url("fonts/source-sans-3-500.woff2") format("woff2");
  font-weight: 500;
  font-style: normal;
  font-display: swap;
}
@font-face {
  font-family: "Source Sans 3";
  src: url("fonts/source-sans-3-600.woff2") format("woff2");
  font-weight: 600;
  font-style: normal;
  font-display: swap;
}

:root {
  --bg: #0c0b09;
  --bg-rail: #0e0d0b;
  --bg-2: #141311;
  --bg-3: #1b1916;
  --ink: #f1ece4;
  --muted: #a8a093;
  --faint: #7a736a;
  --brass: #c4a36a;
  --brass-2: #e4cb96;
  --line: rgba(196, 163, 106, 0.28);
  --line-strong: rgba(196, 163, 106, 0.55);
  --serif: "Source Serif 4", "Palatino Linotype", Palatino, "Iowan Old Style", Georgia, serif;
  --sans: "Source Sans 3", "Segoe UI", "Helvetica Neue", Arial, sans-serif;
  --rail: 292px;
  --shadow: 0 0 0 1px rgba(196, 163, 106, 0.08);
}

* { box-sizing: border-box; }
html { font-size: 17px; color-scheme: dark; }
body {
  margin: 0;
  min-height: 100vh;
  background:
    radial-gradient(900px 420px at 0% 0%, rgba(196, 163, 106, 0.07), transparent 55%),
    var(--bg);
  color: var(--ink);
  font-family: var(--sans);
  font-weight: 400;
  line-height: 1.55;
}
button { font: inherit; color: inherit; cursor: pointer; background: none; border: 0; }
button:focus-visible,
a:focus-visible {
  outline: 1px solid var(--brass);
  outline-offset: 3px;
}
button:disabled { opacity: 0.32; cursor: default; }

.app {
  display: grid;
  grid-template-columns: var(--rail) minmax(0, 1fr);
  height: 100vh;
  height: 100dvh;
}

.rail {
  display: flex;
  flex-direction: column;
  min-height: 0;
  background: var(--bg-rail);
  border-right: 1px solid var(--line);
  padding: 28px 16px 16px;
}
.brand {
  padding: 0 10px 18px;
  border-bottom: 1px solid var(--line);
}
.series {
  margin: 0 0 12px;
  color: var(--brass);
  font-size: 0.68rem;
  font-weight: 600;
  letter-spacing: 0.18em;
  text-transform: uppercase;
}
.brand h1 {
  margin: 0;
  font-family: var(--serif);
  font-weight: 400;
  font-size: 1.48rem;
  line-height: 1.18;
  letter-spacing: -0.02em;
}
.brand h1 span {
  display: block;
  margin-top: 0.28rem;
  color: var(--brass-2);
  font-size: 1.02rem;
}
.rail nav {
  margin-top: 14px;
  overflow: auto;
  min-height: 0;
  padding-right: 4px;
}
.rail ol {
  list-style: none;
  margin: 0;
  padding: 0;
}
.rail li { margin: 0; }
.rail li button {
  width: 100%;
  display: grid;
  grid-template-columns: 2rem minmax(0, 1fr);
  gap: 6px;
  align-items: baseline;
  text-align: left;
  padding: 8px 10px;
  border-radius: 2px;
  color: var(--muted);
  font-size: 0.92rem;
  font-weight: 500;
  line-height: 1.3;
}
.rail li button:hover { color: var(--ink); background: rgba(196, 163, 106, 0.06); }
.rail li button[aria-current="true"] {
  color: var(--ink);
  background: rgba(196, 163, 106, 0.12);
}
.rail .num {
  color: var(--brass);
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.06em;
  font-variant-numeric: tabular-nums;
}
.rail-foot {
  margin-top: auto;
  padding: 16px 10px 4px;
  color: var(--faint);
  font-size: 0.75rem;
  letter-spacing: 0.04em;
}

.stage {
  display: grid;
  grid-template-rows: auto minmax(0, 1fr) auto;
  min-width: 0;
  min-height: 0;
}
.stage-head {
  display: flex;
  justify-content: space-between;
  align-items: center;
  gap: 16px;
  padding: 18px 40px 8px;
}
.kicker {
  margin: 0;
  color: var(--brass);
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.16em;
  text-transform: uppercase;
}
.player {
  display: flex;
  align-items: center;
  gap: 12px;
}
#play {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  border: 1px solid var(--line-strong);
  border-radius: 999px;
  padding: 6px 14px 6px 6px;
  color: var(--brass-2);
  letter-spacing: 0.12em;
  text-transform: uppercase;
  font-size: 0.68rem;
  font-weight: 600;
}
#play:hover { border-color: var(--brass-2); background: rgba(196, 163, 106, 0.08); }
#play .disc {
  width: 30px;
  height: 30px;
  border-radius: 50%;
  border: 1px solid var(--brass);
  display: grid;
  place-items: center;
}
#play svg { display: block; }
#play-status {
  margin: 0;
  min-width: 11rem;
  color: var(--muted);
  font-size: 0.82rem;
}
#play-status.is-missing { color: var(--brass-2); }

#scroller {
  overflow: auto;
  padding: 4px 40px 28px;
}
.slide h2 {
  margin: 0 0 0.55rem;
  max-width: 18ch;
  font-family: var(--serif);
  font-weight: 400;
  font-size: clamp(2rem, 3.4vw, 2.75rem);
  line-height: 1.12;
  letter-spacing: -0.025em;
}
.slide h2:focus { outline: none; }
.lead, .prose p {
  max-width: 66ch;
  margin: 0 0 0.9rem;
  color: var(--ink);
  font-size: 1.02rem;
}
.prose p.quiet, .quiet { color: var(--muted); }
.slide em { font-family: var(--serif); font-style: italic; }

.pair, .split, .gainloss {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 14px;
  max-width: 760px;
  margin: 1.3rem 0 0.4rem;
}
.card {
  background: var(--bg-2);
  border: 1px solid var(--line);
  padding: 16px 18px 18px;
}
.card .label, .triad h3, .illustration .tag, .check .tag, .finding .tag {
  display: block;
  margin: 0 0 8px;
  color: var(--brass);
  font-size: 0.68rem;
  font-weight: 600;
  letter-spacing: 0.16em;
  text-transform: uppercase;
}
.card p, .triad p { margin: 0; }
.card p + p { margin-top: 0.55rem; }

.figure {
  margin: 1rem 0 0.2rem;
  background: var(--bg-2);
  border: 1px solid var(--line);
  padding: 16px 16px 12px;
}
.figure svg { display: block; width: auto; max-width: 100%; height: 248px; margin: 0 auto; }
.flow {
  display: grid;
  grid-template-columns: 1fr auto 1fr auto 1fr;
  gap: 8px;
  align-items: stretch;
  max-width: 820px;
}
.flow .nodebox {
  background: #100f0d;
  border: 1px solid var(--line);
  padding: 16px 14px 14px;
}
.flow .arrow {
  align-self: center;
  color: var(--brass);
  font-family: var(--serif);
  font-size: 1.4rem;
  padding: 0 2px;
}
.nodebox strong {
  display: block;
  font-family: var(--serif);
  font-weight: 400;
  font-size: 1.35rem;
  margin-bottom: 4px;
}
.nodebox span { color: var(--muted); font-size: 0.92rem; }
.notes {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 10px 28px;
  max-width: 760px;
  margin: 1rem 0 0;
  padding: 0;
  list-style: none;
}
.notes li {
  padding-top: 8px;
  border-top: 1px solid var(--line);
  color: var(--muted);
  font-size: 0.95rem;
}

.steps {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 8px;
  margin-top: 14px;
}
.steps button {
  text-align: left;
  background: #100f0d;
  border: 1px solid var(--line);
  padding: 8px 12px 10px;
  min-height: 56px;
  color: var(--ink);
  font-size: 0.92rem;
  line-height: 1.3;
}
.steps button:hover { border-color: var(--line-strong); }
.steps button[aria-pressed="true"] {
  border-color: var(--brass);
  background: rgba(196, 163, 106, 0.12);
}
.steps .idx {
  display: block;
  margin-bottom: 4px;
  color: var(--brass);
  font-size: 0.66rem;
  font-weight: 600;
  letter-spacing: 0.14em;
}
.finding {
  min-height: 4.8em;
  margin: 14px 0 0;
  padding-top: 12px;
  border-top: 1px solid var(--line);
  max-width: 68ch;
}
.finding p {
  margin: 0;
  font-family: var(--serif);
  font-size: 1.18rem;
  line-height: 1.4;
}

svg .card {
  fill: #12110f;
  stroke: rgba(196, 163, 106, 0.38);
  stroke-width: 1.25;
}
svg .glyph {
  fill: none;
  stroke: rgba(196, 163, 106, 0.7);
  stroke-width: 1.5;
}
svg .glyph-fill { fill: rgba(196, 163, 106, 0.2); stroke: none; }
svg text {
  fill: #c9c1b4;
  font-family: var(--sans);
  font-size: 14px;
  font-weight: 500;
}
.node.is-on .card {
  fill: #2c261b;
  stroke: #c4a36a;
  stroke-width: 1.8;
}
.node.is-on text { fill: #f6f1e8; }
.node.is-on .glyph { stroke: #e4cb96; }
.link {
  fill: none;
  stroke: rgba(196, 163, 106, 0.62);
  stroke-width: 1.75;
}
.link.is-on { stroke: #c4a36a; stroke-width: 2.25; }

.stack-layout {
  display: grid;
  grid-template-columns: 52px minmax(0, 1fr) 52px;
  gap: 10px;
  align-items: stretch;
  max-width: 760px;
}
.stack {
  display: flex;
  flex-direction: column;
  gap: 5px;
}
.layer, .cross {
  border: 1px solid var(--line);
  background: #161410;
  color: var(--ink);
  text-align: left;
}
.layer {
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 12px;
  padding: 0 16px;
}
.layer .lwhere { color: var(--muted); font-size: 0.85rem; }
.layer[data-depth="1"] { min-height: 40px; margin-inline: 14%; background: #24211c; }
.layer[data-depth="2"] { min-height: 44px; margin-inline: 11%; background: #201e19; }
.layer[data-depth="3"] { min-height: 48px; margin-inline: 8%; background: #1c1a16; }
.layer[data-depth="4"] { min-height: 54px; margin-inline: 5%; background: #181714; }
.layer[data-depth="5"] { min-height: 60px; margin-inline: 2.5%; background: #141311; }
.layer[data-depth="6"] {
  min-height: 68px;
  margin-inline: 0;
  background: #0e0d0b;
  border-width: 2px;
  font-size: 1.05rem;
}
.layer[aria-pressed="true"], .cross[aria-pressed="true"] {
  border-color: var(--brass);
  background: #2c261b;
}
.cross {
  writing-mode: vertical-rl;
  transform: rotate(180deg);
  letter-spacing: 0.16em;
  text-transform: uppercase;
  font-size: 0.68rem;
  font-weight: 600;
  color: var(--brass-2);
}
.cross:hover, .layer:hover { border-color: var(--line-strong); }
.stack-caption {
  max-width: 760px;
  margin: 8px 0 0;
  color: var(--faint);
  font-size: 0.82rem;
}
.triad {
  display: grid;
  grid-template-columns: repeat(3, minmax(0, 1fr));
  gap: 10px;
  max-width: 760px;
  margin-top: 12px;
}
.triad section {
  background: #100f0d;
  border: 1px solid var(--line);
  padding: 12px 14px 14px;
  min-height: 0;
}
.triad p { color: var(--ink); font-size: 0.95rem; }

.orbit-wrap { max-width: 720px; margin-top: 0.4rem; }
.orbit-wrap .finding { min-height: 0; margin: 0 0 8px; padding-top: 0; border-top: 0; }
.orbit {
  position: relative;
  height: 400px;
}
.orbit::before {
  content: "";
  position: absolute;
  left: 50%;
  top: 50%;
  width: 280px;
  height: 280px;
  transform: translate(-50%, -50%);
  border: 1px solid rgba(196, 163, 106, 0.22);
  border-radius: 50%;
  opacity: 0;
}
.orbit.revealed::before { opacity: 1; }
.core, .sat {
  position: absolute;
  left: 50%;
  top: 50%;
  display: grid;
  place-items: center;
  text-align: center;
  border-radius: 50%;
  border: 1px solid var(--line-strong);
  background: #14120f;
  line-height: 1.25;
  padding: 8px;
}
.core {
  width: 120px;
  height: 120px;
  transform: translate(-50%, -50%);
  font-family: var(--serif);
  font-size: 1.2rem;
  z-index: 1;
}
.core small {
  display: block;
  margin-top: 4px;
  font-family: var(--sans);
  font-size: 0.68rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--brass);
}
.sat {
  width: 100px;
  height: 100px;
  font-size: 0.86rem;
  transform: translate(-50%, -50%) rotate(var(--a)) translateY(-136px) rotate(calc(var(--a) * -1));
  opacity: 0;
  visibility: hidden;
  pointer-events: none;
}
.orbit.revealed .sat {
  opacity: 1;
  visibility: visible;
  pointer-events: auto;
}
.sat[aria-pressed="true"], .core[aria-pressed="true"] {
  border-color: var(--brass-2);
  background: #2c261b;
  color: var(--ink);
}
.hint { color: var(--muted); margin: 0; max-width: 60ch; }

.illustration {
  max-width: 66ch;
  margin: 0.85rem 0 0;
  padding: 2px 0 2px 14px;
  border-left: 2px solid var(--brass);
}
.illustration p { margin: 0; color: var(--muted); }

.check {
  max-width: 66ch;
  margin-top: 0.9rem;
  padding: 16px 18px 18px;
  border: 1px solid var(--line-strong);
  background: rgba(196, 163, 106, 0.05);
}
.check .ask {
  margin: 0;
  font-family: var(--serif);
  font-size: 1.28rem;
  line-height: 1.35;
}
.check button {
  margin-top: 14px;
  border: 1px solid var(--brass);
  color: var(--brass-2);
  padding: 8px 14px;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  font-size: 0.7rem;
  font-weight: 600;
}
.check button:hover { background: rgba(196, 163, 106, 0.1); }
.check .answer {
  margin: 14px 0 0;
  font-family: var(--serif);
  font-size: 1.22rem;
  line-height: 1.4;
}

.modes {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 8px 18px;
  max-width: 720px;
  margin: 0.4rem 0 1rem;
  padding: 0;
  list-style: none;
}
.modes li {
  padding: 10px 0;
  border-top: 1px solid var(--line);
}
.modes strong {
  display: block;
  font-weight: 600;
  color: var(--brass-2);
  font-size: 0.78rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  margin-bottom: 3px;
}

.four {
  display: grid;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 10px;
  margin: 0.6rem 0 1rem;
  max-width: 860px;
}
.four article {
  background: var(--bg-2);
  border: 1px solid var(--line);
  padding: 14px 12px 16px;
  min-height: 9.5rem;
}
.four .n {
  color: var(--brass);
  font-size: 0.68rem;
  letter-spacing: 0.14em;
  font-weight: 600;
}
.four h3 {
  margin: 6px 0 8px;
  font-family: var(--serif);
  font-weight: 400;
  font-size: 1.25rem;
}

.fails {
  max-width: 720px;
  margin: 0.2rem 0 1rem;
  padding: 0;
  list-style: none;
}
.fails li {
  display: grid;
  grid-template-columns: 11rem minmax(0, 1fr);
  gap: 12px;
  padding: 9px 0;
  border-top: 1px solid var(--line);
}
.fails li span { color: var(--brass-2); font-weight: 600; }

.questions { max-width: 760px; border-bottom: 1px solid var(--line); }
.q button {
  width: 100%;
  display: grid;
  grid-template-columns: 2rem minmax(0, 1fr) auto;
  gap: 10px;
  align-items: baseline;
  text-align: left;
  padding: 13px 4px;
  border-top: 1px solid var(--line);
  font-size: 1.02rem;
}
.q button:hover { color: var(--brass-2); }
.q .qn { color: var(--brass); font-size: 0.72rem; letter-spacing: 0.08em; font-weight: 600; }
.q .mk { color: var(--brass); font-family: var(--serif); font-size: 1.2rem; line-height: 1; }
.q .body {
  margin: 0;
  padding: 0 28px 14px 2.6rem;
  color: var(--muted);
  max-width: 62ch;
}

.standing {
  margin: 0.4rem 0 1.1rem;
  max-width: 20ch;
  font-family: var(--serif);
  font-weight: 400;
  font-size: clamp(1.7rem, 3vw, 2.35rem);
  line-height: 1.22;
}
.three {
  display: grid;
  gap: 0;
  max-width: 640px;
}
.three div {
  padding: 12px 0;
  border-top: 1px solid var(--line);
}
.three strong {
  display: block;
  color: var(--brass);
  font-size: 0.68rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  font-weight: 600;
  margin-bottom: 4px;
}

.narration {
  max-width: 68ch;
  margin-top: 1.6rem;
  padding-top: 14px;
  border-top: 1px solid var(--line-strong);
}
.narration .notice {
  margin: 0 0 10px;
  color: var(--brass-2);
  font-size: 0.72rem;
  font-weight: 600;
  letter-spacing: 0.14em;
  text-transform: uppercase;
}
.narration .script {
  margin: 0;
  font-family: var(--serif);
  font-size: 1.05rem;
  line-height: 1.65;
  color: #ddd6cb;
}

.pager {
  display: grid;
  grid-template-columns: 1fr auto 1fr;
  align-items: center;
  gap: 12px;
  padding: 12px 28px 14px;
  border-top: 1px solid var(--line);
  background: rgba(12, 11, 9, 0.92);
}
.pager .navbtn {
  border: 1px solid var(--line);
  min-width: 7.5rem;
  padding: 8px 16px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  font-size: 0.7rem;
  font-weight: 600;
  color: var(--brass-2);
}
#back { justify-self: start; }
#next { justify-self: end; }
.pager .navbtn:hover:not(:disabled) { border-color: var(--brass); background: rgba(196, 163, 106, 0.08); }
.progress { text-align: center; }
.progress #count {
  display: block;
  font-variant-numeric: tabular-nums;
  letter-spacing: 0.08em;
  font-size: 0.85rem;
}
.colophon {
  display: block;
  margin-top: 3px;
  color: var(--faint);
  font-size: 0.72rem;
  letter-spacing: 0.08em;
}
.keys {
  display: block;
  margin-top: 2px;
  color: var(--faint);
  font-size: 0.68rem;
  letter-spacing: 0.06em;
}

.sr {
  position: absolute;
  width: 1px;
  height: 1px;
  padding: 0;
  margin: -1px;
  overflow: hidden;
  clip: rect(0, 0, 0, 0);
  white-space: nowrap;
  border: 0;
}
.noscript {
  padding: 24px;
  font-family: var(--serif);
}

@media (max-width: 980px) {
  .app {
    grid-template-columns: 1fr;
    grid-template-rows: auto minmax(0, 1fr);
    height: auto;
    min-height: 100dvh;
  }
  .rail { border-right: 0; border-bottom: 1px solid var(--line); max-height: none; }
  .rail nav { max-height: 180px; }
  .stage { min-height: 70dvh; }
  .stage-head, #scroller { padding-left: 20px; padding-right: 20px; }
  .steps { grid-template-columns: 1fr 1fr; }
  .four { grid-template-columns: 1fr 1fr; }
  .fails li { grid-template-columns: 1fr; gap: 2px; }
  .pair, .split, .gainloss, .notes, .modes { grid-template-columns: 1fr; }
  .flow { grid-template-columns: 1fr; }
  .flow .arrow { transform: rotate(90deg); justify-self: center; }
  .triad { grid-template-columns: 1fr; }
  .orbit { height: 520px; }
  .sat { transform: translate(-50%, -50%) rotate(var(--a)) translateY(-108px) rotate(calc(var(--a) * -1)); }
  .orbit::before { width: 264px; height: 264px; }
  #play-status { display: none; }
  .player #play-status.is-missing { display: block; }
}

@media (prefers-reduced-motion: reduce) {
  * { scroll-behavior: auto !important; transition: none !important; animation: none !important; }
}

.orbit {
  height: auto;
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 14px;
}
.orbit::before { display: none; }
.orbit .core {
  position: relative;
  left: auto;
  top: auto;
  transform: none;
  margin: 4px 0 2px;
}
.copies {
  display: none;
  width: 100%;
  grid-template-columns: repeat(4, minmax(0, 1fr));
  gap: 8px;
}
.orbit.revealed .copies { display: grid; }
.orbit .sat {
  position: relative;
  left: auto;
  top: auto;
  width: auto;
  height: auto;
  min-height: 64px;
  border-radius: 2px;
  transform: none;
  opacity: 1;
  visibility: visible;
  pointer-events: auto;
}
@media (max-width: 980px) {
  .orbit { height: auto; }
  .copies { grid-template-columns: 1fr 1fr; }
  .orbit .sat { transform: none; }
}