/* ════════════════════════════════════════════════════════════════
   whitepaper.css — a light, technical-paper treatment of the
   portfolio. Cool paper · ink text · one deep signal-blue accent.
   Grotesk display + mono data. arXiv-meets-Stripe-docs.
   A de-anchored alternative to the dark "Determinism Layer" skin.
   ════════════════════════════════════════════════════════════════ */

:root {
  /* ── Surface (cool paper, never pure white) ──────────────── */
  --paper:        #F4F5F6;
  --paper-raised: #FBFBFC;

  /* ── Hairlines ───────────────────────────────────────────── */
  --rule:         #E4E6E9;
  --rule-strong:  #CDD1D6;

  /* ── Ink (cool near-black, never pure black) ─────────────── */
  --ink:          #14161A;
  --ink-muted:    #565B62;
  --ink-faint:    #8A9099;

  /* ── Accent — deep signal blue, used with intent ─────────── */
  --accent:       #1B3BD8;
  --accent-deep:  #142C9E;
  --accent-soft:  rgba(27, 59, 216, 0.07);
  --accent-line:  rgba(27, 59, 216, 0.32);
  --on-accent:    #FFFFFF;

  /* ── Type ────────────────────────────────────────────────── */
  --grotesk: "Space Grotesk", system-ui, sans-serif;  /* display + UI */
  --mono:    "IBM Plex Mono", ui-monospace, monospace; /* data / labels */

  --text-xs:   0.6875rem;
  --text-sm:   0.8125rem;
  --text-base: 1rem;
  --text-lg:   1.1875rem;
  --text-xl:   1.5rem;
  --text-2xl:  1.9375rem;
  --text-stat: 2.75rem;

  --r: 2px;

  --maxw: 860px;
  --pad:  clamp(1.25rem, 5vw, 3rem);
}

*, *::before, *::after { box-sizing: border-box; margin: 0; padding: 0; }
html { scroll-behavior: smooth; }
body {
  background: var(--paper);
  color: var(--ink);
  font-family: var(--grotesk);
  font-size: var(--text-base);
  font-weight: 400;
  line-height: 1.6;
  -webkit-font-smoothing: antialiased;
  -moz-osx-font-smoothing: grayscale;
  /* faint engineering-paper grid, fixed, non-scrolling */
  background-image:
    linear-gradient(var(--rule) 1px, transparent 1px),
    linear-gradient(90deg, var(--rule) 1px, transparent 1px);
  background-size: 44px 44px;
  background-position: center top;
  background-attachment: fixed;
}
/* soften the grid so it reads as a watermark, not a table */
body::before {
  content: "";
  position: fixed;
  inset: 0;
  background: var(--paper);
  opacity: 0.86;
  z-index: -1;
  pointer-events: none;
}

.mono {
  font-family: var(--mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--ink-faint);
}

/* ── Masthead ────────────────────────────────────────────────── */
.masthead {
  position: sticky;
  top: 0;
  z-index: 50;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
  height: 60px;
  padding: 0 var(--pad);
  background: rgba(244, 245, 246, 0.82);
  backdrop-filter: blur(12px);
  -webkit-backdrop-filter: blur(12px);
  border-bottom: 1px solid var(--rule);
}
.masthead .wordmark {
  font-family: var(--mono);
  font-size: var(--text-sm);
  letter-spacing: 0.06em;
  color: var(--ink);
  font-weight: 500;
}
.masthead .wordmark .reg {
  color: var(--ink-faint);
  font-weight: 400;
}
.masthead nav { display: flex; align-items: center; gap: 1.25rem; }
.masthead nav a {
  font-family: var(--mono);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  text-decoration: none;
  color: var(--ink-muted);
  transition: color 0.15s ease;
}
.masthead nav a:hover { color: var(--ink); }
.masthead nav a.cta {
  color: var(--on-accent);
  background: var(--accent);
  border-radius: var(--r);
  padding: 7px 13px;
  transition: background 0.15s ease;
}
.masthead nav a.cta:hover { background: var(--accent-deep); color: var(--on-accent); }
.masthead nav a:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; border-radius: 1px; }

/* ── Shell ───────────────────────────────────────────────────── */
main { max-width: var(--maxw); margin: 0 auto; padding: 0 var(--pad); }

a.link {
  color: var(--accent-deep);
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 3px;
  text-decoration-color: var(--accent-line);
  transition: text-decoration-color 0.15s ease;
}
a.link:hover { text-decoration-color: var(--accent-deep); }
a:focus-visible { outline: 2px solid var(--accent); outline-offset: 2px; border-radius: 1px; }

/* ── Title block (the paper's masthead title) ────────────────── */
.title-block { padding: clamp(3rem, 8vw, 5.5rem) 0 clamp(2rem, 5vw, 3rem); }
.title-block h1 {
  font-family: var(--grotesk);
  font-weight: 500;
  font-size: clamp(1.95rem, 4.6vw, 3.1rem);
  line-height: 1.12;
  letter-spacing: -0.025em;
  color: var(--ink);
  max-width: 20ch;
}
.title-block h1 .lo { color: var(--ink-faint); font-weight: 400; }
.title-block h1 .accent { color: var(--accent-deep); }
.byline {
  margin-top: 1.5rem;
  font-family: var(--mono);
  font-size: var(--text-sm);
  letter-spacing: 0.02em;
  color: var(--ink-muted);
}
.byline .status {
  display: inline-flex;
  align-items: center;
  gap: 0.4rem;
  color: var(--accent-deep);
}
.byline .status .live {
  width: 6px; height: 6px; border-radius: 50%;
  background: var(--accent);
  box-shadow: 0 0 0 3px var(--accent-soft);
}
.abstract {
  margin-top: 1.75rem;
  max-width: 58ch;
  font-size: var(--text-lg);
  line-height: 1.62;
  color: var(--ink-muted);
}
.abstract em { color: var(--ink); font-style: italic; }
.title-cta {
  margin-top: 1.75rem;
  font-family: var(--mono);
  font-size: var(--text-sm);
  letter-spacing: 0.02em;
}

/* ── Figure ──────────────────────────────────────────────────── */
.figure {
  margin: clamp(1.5rem, 4vw, 2.5rem) 0 0;
  padding-top: clamp(1.75rem, 4vw, 2.5rem);
  border-top: 1px solid var(--rule);
}
.figure-head {
  display: flex;
  align-items: baseline;
  gap: 0.75rem;
  margin-bottom: 1.25rem;
}
.figure-head .fig-no {
  font-family: var(--mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--accent-deep);
  font-weight: 500;
}
.figure-head .fig-title {
  font-family: var(--mono);
  font-size: var(--text-xs);
  letter-spacing: 0.04em;
  color: var(--ink-muted);
}
.figure-head .fig-hint {
  margin-left: auto;
  font-family: var(--mono);
  font-size: 0.625rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--ink-faint);
}
.viz {
  position: relative;
  width: 100%;
  aspect-ratio: 920 / 320;
  cursor: pointer;
  background: var(--paper-raised);
  border: 1px solid var(--rule);
  border-radius: var(--r);
}
.viz canvas { position: absolute; inset: 0; width: 100%; height: 100%; display: block; }
.figure-cap {
  margin-top: 0.85rem;
  font-family: var(--mono);
  font-size: var(--text-xs);
  letter-spacing: 0.02em;
  color: var(--ink-faint);
}

/* ── Section head ────────────────────────────────────────────── */
.section-head {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 1rem;
  margin-top: clamp(3.5rem, 8vw, 5.5rem);
  padding-bottom: 0.85rem;
  border-bottom: 2px solid var(--ink);
}
.section-head h2 {
  font-family: var(--grotesk);
  font-weight: 500;
  font-size: var(--text-xl);
  letter-spacing: -0.02em;
  color: var(--ink);
}
.section-head .range { font-family: var(--mono); font-size: var(--text-xs); letter-spacing: 0.1em; text-transform: uppercase; color: var(--ink-faint); }

/* ── Era (paper section) ─────────────────────────────────────── */
.era { padding: clamp(2.25rem, 5vw, 3.25rem) 0; }
.era + .era { border-top: 1px solid var(--rule); }

/* the ledger-baseline: §N · company · role ...... dates */
.era-line {
  display: flex;
  align-items: baseline;
  gap: 0.75rem;
}
.era-sec {
  font-family: var(--mono);
  font-size: var(--text-sm);
  font-weight: 500;
  color: var(--accent-deep);
  flex-shrink: 0;
}
.era-company {
  font-family: var(--grotesk);
  font-weight: 500;
  font-size: var(--text-2xl);
  letter-spacing: -0.02em;
  color: var(--ink);
  line-height: 1;
  flex-shrink: 0;
}
.era-dates {
  font-family: var(--mono);
  font-size: var(--text-xs);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--ink-faint);
  flex-shrink: 0;
}
.leader {
  flex: 1;
  height: 0;
  border-bottom: 1px dotted var(--rule-strong);
  transform: translateY(-0.28em);
  min-width: 1.5rem;
}
.era-role {
  margin-top: 0.6rem;
  font-size: var(--text-sm);
  color: var(--ink-muted);
}

/* the headline stat, on its own ledger baseline */
.era-stat-row {
  display: flex;
  align-items: baseline;
  gap: 0.75rem;
  margin-top: 1.25rem;
}
.era-stat-row .stat-key {
  font-family: var(--mono);
  font-size: var(--text-xs);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--ink-faint);
  flex-shrink: 0;
}
.era-stat-row .stat-num {
  font-family: var(--grotesk);
  font-weight: 500;
  font-size: var(--text-stat);
  color: var(--accent-deep);
  line-height: 0.9;
  letter-spacing: -0.03em;
  flex-shrink: 0;
}

.era-intro {
  margin-top: 1.5rem;
  max-width: 66ch;
  font-size: var(--text-base);
  line-height: 1.68;
  color: var(--ink-muted);
}
.era-intro em { color: var(--ink); font-style: italic; }

.chips { display: flex; flex-wrap: wrap; gap: 0.4rem; margin-top: 1.25rem; list-style: none; }
.chip {
  font-family: var(--mono);
  font-size: var(--text-xs);
  letter-spacing: 0.04em;
  color: var(--ink-muted);
  background: var(--paper-raised);
  border: 1px solid var(--rule);
  padding: 3px 9px;
  border-radius: var(--r);
}

/* ── Project list (hairline rows, not cards) ─────────────────── */
.projects {
  margin-top: 2rem;
  display: grid;
  grid-template-columns: 1fr 1fr;
  column-gap: 2.5rem;
  row-gap: 0;
}
.projects.single { grid-template-columns: 1fr; }
.project {
  display: block;
  text-decoration: none;
  color: inherit;
  padding: 1.35rem 0;
  border-top: 1px solid var(--rule);
  transition: border-color 0.2s ease;
}
a.project:hover { border-top-color: var(--accent); }
.project-top {
  display: flex;
  align-items: baseline;
  justify-content: space-between;
  gap: 0.75rem;
}
.project-name {
  font-family: var(--grotesk);
  font-weight: 500;
  font-size: var(--text-lg);
  letter-spacing: -0.01em;
  color: var(--ink);
}
a.project:hover .project-name { color: var(--accent-deep); }
.project-arrow {
  font-family: var(--mono);
  font-size: var(--text-xs);
  color: var(--ink-faint);
  opacity: 0;
  transform: translateX(-4px);
  transition: opacity 0.2s ease, transform 0.2s ease;
}
a.project:hover .project-arrow { opacity: 1; transform: none; }
.project p {
  margin-top: 0.6rem;
  font-size: var(--text-sm);
  line-height: 1.6;
  color: var(--ink-muted);
}
.project .metric {
  display: inline-flex;
  align-items: baseline;
  gap: 0.45rem;
  margin-top: 0.9rem;
  font-family: var(--mono);
  font-size: var(--text-xs);
  letter-spacing: 0.04em;
  color: var(--ink-faint);
}
.project .metric b {
  font-family: var(--grotesk);
  font-weight: 500;
  font-size: var(--text-base);
  color: var(--accent-deep);
  letter-spacing: -0.01em;
}

/* ── Footer ──────────────────────────────────────────────────── */
.foot {
  max-width: var(--maxw);
  margin: 0 auto;
  padding: clamp(3.5rem, 8vw, 5.5rem) var(--pad) 4rem;
  border-top: 2px solid var(--ink);
}
.foot .foot-mark { font-family: var(--mono); font-size: var(--text-xs); letter-spacing: 0.1em; text-transform: uppercase; color: var(--ink-faint); }
.foot .foot-cta {
  display: inline-block;
  margin: 1rem 0 1.75rem;
  font-family: var(--grotesk);
  font-weight: 500;
  font-size: var(--text-2xl);
  letter-spacing: -0.02em;
  color: var(--ink);
  text-decoration: none;
  transition: color 0.15s ease;
}
.foot .foot-cta:hover { color: var(--accent-deep); }
.foot .foot-cta .arr { color: var(--accent-deep); }
.foot .corr {
  font-family: var(--mono);
  font-size: var(--text-xs);
  letter-spacing: 0.04em;
  color: var(--ink-muted);
}
.foot .corr a { color: var(--accent-deep); text-decoration: none; }
.foot .corr a:hover { text-decoration: underline; text-underline-offset: 3px; }

/* ── Reveal-on-scroll ────────────────────────────────────────── */
.reveal { opacity: 0; transform: translateY(14px); transition: opacity 0.55s ease, transform 0.55s ease; }
.reveal.in { opacity: 1; transform: none; }

/* ── Mobile ──────────────────────────────────────────────────── */
@media (max-width: 720px) {
  .projects { grid-template-columns: 1fr; column-gap: 0; }
  .era-line { flex-wrap: wrap; gap: 0.5rem; }
  .leader { display: none; }
  .era-dates { order: 3; flex-basis: 100%; }
  .era-stat-row .stat-num { font-size: 2.25rem; }
  .figure-head { flex-wrap: wrap; }
  .figure-head .fig-hint { margin-left: 0; flex-basis: 100%; }
}

/* ── Reduced motion ──────────────────────────────────────────── */
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after { transition-duration: 0.01ms !important; }
  .reveal { opacity: 1; transform: none; }
}