/* ============================================================
   Sheet 01 — SpaceLayoutGym BC+PPO
   Aesthetic: architectural drawing sheet meets editorial print.
   ============================================================ */

:root {
  --paper:        #f1ece1;   /* warm trace paper */
  --paper-2:      #e9e2d2;   /* darker pinstripe */
  --ink:          #16140f;   /* near-black with warmth */
  --ink-soft:     #4b463c;
  --rule:         rgba(22, 20, 15, 0.18);
  --rule-strong:  rgba(22, 20, 15, 0.55);
  --accent:       #b8321c;   /* drafting red */
  --accent-deep:  #7a1f10;
  --link:         #1d3a7e;   /* ink blue */

  --serif: "Instrument Serif", ui-serif, Georgia, serif;
  --sans:  "Inter", ui-sans-serif, system-ui, -apple-system, "Segoe UI", sans-serif;
  --mono:  "JetBrains Mono", ui-monospace, "SFMono-Regular", Menlo, monospace;

  --gutter: clamp(20px, 5vw, 56px);
  --max:    1180px;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; }

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--sans);
  font-size: 17px;
  line-height: 1.55;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

/* Faint drafting grid behind everything */
.sheet-grid {
  position: fixed;
  inset: 0;
  pointer-events: none;
  background-image:
    linear-gradient(to right, rgba(22, 20, 15, 0.045) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(22, 20, 15, 0.045) 1px, transparent 1px);
  background-size: 32px 32px;
  z-index: 0;
}

/* Scroll progress hairline at top */
.scroll-progress {
  position: fixed;
  top: 0;
  left: 0;
  right: 0;
  height: 2px;
  background: var(--accent);
  transform-origin: 0 50%;
  transform: scaleX(0);
  z-index: 50;
  transition: transform 100ms linear;
}

img { display: block; max-width: 100%; }
a { color: var(--link); text-underline-offset: 3px; }

/* ============================================================
   Left margin index — fixed on desktop, hidden on mobile
   ============================================================ */
.margin-index {
  position: fixed;
  top: 50%;
  left: clamp(12px, 2.6vw, 28px);
  transform: translateY(-50%);
  z-index: 10;
  font-family: var(--mono);
  font-size: 11px;
  letter-spacing: 0.04em;
}

.margin-label {
  margin: 0 0 12px;
  color: var(--ink-soft);
  text-transform: uppercase;
  font-weight: 700;
  letter-spacing: 0.18em;
}

.margin-index ol {
  margin: 0;
  padding: 0;
  list-style: none;
  border-left: 1px solid var(--rule-strong);
}

.margin-index li a {
  display: flex;
  align-items: baseline;
  gap: 10px;
  padding: 8px 14px;
  color: var(--ink-soft);
  text-decoration: none;
  transition: color 160ms ease, transform 160ms ease;
}

.margin-index li a span {
  display: inline-block;
  width: 18px;
  color: var(--accent);
  font-weight: 700;
}

.margin-index li a:hover,
.margin-index li a:focus-visible {
  color: var(--ink);
  transform: translateX(2px);
}

@media (max-width: 1100px) {
  .margin-index { display: none; }
}

/* ============================================================
   Main column
   ============================================================ */
main {
  position: relative;
  z-index: 1;
  max-width: var(--max);
  margin: 0 auto;
  padding: clamp(20px, 4vw, 40px) var(--gutter) clamp(60px, 8vw, 120px);
}

/* ============================================================
   Title block — like the metadata box on a drawing sheet
   ============================================================ */
.title-block {
  position: relative;
  margin-top: clamp(16px, 4vw, 36px);
  border: 1px solid var(--rule-strong);
  background: rgba(255, 253, 247, 0.55);
  backdrop-filter: blur(2px);
}

/* Top + bottom metadata rows */
.title-block__row {
  display: flex;
  flex-wrap: wrap;
  align-items: stretch;
  border-bottom: 1px solid var(--rule);
}

.title-block__row--bottom {
  border-bottom: none;
  border-top: 1px solid var(--rule);
}

.kv {
  display: flex;
  flex-direction: column;
  gap: 2px;
  padding: 10px 18px;
  flex: 1 1 0;
  min-width: 0;
  border-right: 1px solid var(--rule);
  font-family: var(--mono);
}

.kv:last-child { border-right: none; }

.kv .k {
  font-size: 10px;
  text-transform: uppercase;
  letter-spacing: 0.16em;
  color: var(--ink-soft);
  font-weight: 700;
}

.kv .v {
  font-size: 13px;
  color: var(--ink);
}

/* Hero block (title, byline, glyph) */
.title-block__hero {
  position: relative;
  min-height: clamp(360px, 48vw, 560px);
  padding: clamp(28px, 5vw, 56px) clamp(24px, 5vw, 56px);
  overflow: hidden;
}

.title-block__hero::before {
  content: "";
  position: absolute;
  inset: 0;
  background: linear-gradient(90deg, rgba(255, 253, 247, 0.98) 0%, rgba(255, 253, 247, 0.88) 48%, rgba(255, 253, 247, 0.22) 100%);
  pointer-events: none;
  z-index: 1;
}

.title-block__hero > * {
  position: relative;
  z-index: 2;
}

.hero-diagram {
  position: absolute;
  z-index: 0;
  top: 50%;
  right: clamp(20px, 4vw, 56px);
  width: min(52%, 560px);
  max-height: 82%;
  object-fit: contain;
  transform: translateY(-50%);
  opacity: 0.42;
  filter: saturate(0.85) contrast(1.05);
}

.overline {
  margin: 0 0 22px;
  font-family: var(--mono);
  font-size: 11px;
  text-transform: uppercase;
  letter-spacing: 0.22em;
  color: var(--accent-deep);
  font-weight: 700;
}

.title-block h1 {
  margin: 0;
  font-family: var(--serif);
  font-weight: 400;
  font-size: clamp(1.55rem, 2.8vw, 2.35rem);
  line-height: 1.12;
  letter-spacing: -0.01em;
  max-width: 23ch;
}

.title-block h1 em {
  color: var(--accent);
  font-style: italic;
}

.title-blue {
  color: var(--link);
}

.title-line { display: block; }

.byline {
  margin: clamp(28px, 4vw, 40px) 0 4px;
  font-family: var(--mono);
  font-size: 13px;
  letter-spacing: 0.02em;
  color: var(--ink);
}

.byline .sep { margin: 0 10px; color: var(--ink-soft); }

.affiliation {
  margin: 0;
  font-family: var(--mono);
  font-size: 12px;
  color: var(--ink-soft);
}

/* Chip-style link row in bottom of title block */
.chip {
  display: flex;
  align-items: center;
  gap: 10px;
  flex: 1 1 0;
  min-width: 0;
  padding: 14px 18px;
  border-right: 1px solid var(--rule);
  font-family: var(--mono);
  font-size: 12px;
  text-decoration: none;
  color: var(--ink);
  text-transform: uppercase;
  letter-spacing: 0.14em;
  transition: background 160ms ease, color 160ms ease;
}

.chip:last-child { border-right: none; }

.chip__num {
  color: var(--accent);
  font-weight: 700;
}

.chip:hover,
.chip:focus-visible {
  background: var(--ink);
  color: var(--paper);
}

.chip:hover .chip__num,
.chip:focus-visible .chip__num { color: var(--paper); }

/* ============================================================
   Bays — numbered content sections
   ============================================================ */
.bay {
  position: relative;
  padding: clamp(56px, 8vw, 96px) 0 0;
}

.bay__head {
  position: relative;
  display: grid;
  grid-template-columns: clamp(48px, 8vw, 92px) 1fr;
  column-gap: clamp(16px, 3vw, 32px);
  align-items: end;
  margin-bottom: clamp(28px, 4vw, 48px);
  padding-bottom: 20px;
  border-bottom: 1px solid var(--rule-strong);
}

.bay__num {
  font-family: var(--serif);
  font-size: clamp(2.2rem, 7vw, 5rem);
  line-height: 0.9;
  color: var(--accent);
  font-style: italic;
}

.bay__kicker {
  grid-column: 2;
  margin: 0 0 8px;
  font-family: var(--mono);
  font-size: 12px;
  color: var(--ink-soft);
  letter-spacing: 0.08em;
}

.bay__title {
  grid-column: 2;
  margin: 0;
  max-width: 760px;
  font-size: clamp(1.55rem, 2.8vw, 2.6rem);
  line-height: 1.12;
  font-weight: 700;
}

.bay__body {
  display: grid;
  gap: clamp(24px, 4vw, 44px);
}

.two-col {
  grid-template-columns: minmax(0, 1fr) minmax(0, 1fr);
}

.figure-led {
  grid-template-columns: minmax(0, 1.45fr) minmax(280px, 0.55fr);
}

.framework-split {
  grid-template-columns: minmax(260px, 0.42fr) minmax(0, 0.58fr);
  align-items: start;
}

.framework-copy {
  font-size: 1.02rem;
  color: var(--ink-soft);
}

.framework-copy p:first-child {
  margin-top: 28px;
}

.bay__body--gap {
  margin-top: clamp(28px, 5vw, 56px);
}

.lead {
  font-size: 1.08rem;
}

.dropcap {
  float: left;
  margin: 0.03em 0.12em 0 0;
  font-family: var(--serif);
  font-size: 3.6rem;
  line-height: 0.82;
  color: var(--accent);
}

.callout {
  margin-top: clamp(24px, 4vw, 40px);
  padding: 20px 24px;
  border-left: 4px solid var(--accent);
  background: rgba(255, 253, 247, 0.5);
}

.callout__tag {
  display: block;
  margin-bottom: 8px;
  font-family: var(--mono);
  font-size: 11px;
  color: var(--accent);
  text-transform: uppercase;
  letter-spacing: 0.14em;
  font-weight: 700;
}

.callout p,
.plate figcaption,
.prior-work {
  margin: 0;
  color: var(--ink-soft);
}

.spec-list {
  display: grid;
  gap: 14px;
  margin: 24px 0 0;
}

.spec-list div {
  display: grid;
  grid-template-columns: 92px 1fr;
  gap: 16px;
  padding-top: 12px;
  border-top: 1px solid var(--rule);
}

.spec-list dt {
  font-family: var(--mono);
  font-size: 12px;
  color: var(--accent);
  font-weight: 700;
  text-transform: uppercase;
}

.spec-list dd {
  margin: 0;
  color: var(--ink-soft);
}

.plate {
  margin: 0;
}

.plate--wide {
  margin-bottom: clamp(28px, 5vw, 56px);
}

.plate__head {
  display: flex;
  gap: 10px;
  align-items: baseline;
  margin-bottom: 8px;
  font-family: var(--mono);
  font-size: 12px;
}

.plate__num {
  color: var(--accent);
  font-weight: 700;
}

.plate__title {
  color: var(--ink);
}

.plate__frame {
  border: 1px solid var(--rule);
  background: rgba(255, 253, 247, 0.75);
  padding: clamp(10px, 2vw, 18px);
}

.plate__frame img {
  width: 100%;
  max-height: 760px;
  object-fit: contain;
  background: #fff;
}

.plate figcaption {
  margin-top: 10px;
  font-size: 0.96rem;
}

.text-link {
  display: inline-block;
  margin-top: 12px;
  font-weight: 700;
}

.bibtex {
  overflow-x: auto;
  padding: 22px;
  border: 1px solid var(--rule-strong);
  background: rgba(255, 253, 247, 0.7);
  font-family: var(--mono);
  font-size: 0.9rem;
}

.prior-work {
  margin-top: 18px;
}

.colophon {
  position: relative;
  z-index: 1;
  border-top: 1px solid var(--rule-strong);
}

.colophon__inner {
  max-width: var(--max);
  margin: 0 auto;
  padding: 22px var(--gutter);
  display: flex;
  justify-content: space-between;
  gap: 20px;
  color: var(--ink-soft);
  font-size: 0.9rem;
}

.colophon p {
  margin: 0;
}

@media (max-width: 760px) {
  body {
    font-size: 16px;
  }

  main {
    padding-inline: 18px;
  }

  .bay__head {
    grid-template-columns: 58px 1fr;
    column-gap: 16px;
    align-items: start;
  }

  .bay__num {
    font-size: 3.4rem;
  }

  .bay__title {
    font-size: clamp(1.45rem, 7vw, 2rem);
  }

  .two-col,
  .figure-led,
  .framework-split,
  .spec-list div {
    grid-template-columns: 1fr;
  }

  .colophon__inner,
  .title-block__row {
    flex-direction: column;
  }

  .kv,
  .chip {
    border-right: none;
    border-bottom: 1px solid var(--rule);
  }
}