/* ==========================================================================
   H Heuristics — research platform
   A printed-page aesthetic: hairline rules, hanging metadata, serif prose.
   ========================================================================== */

:root {
  --paper:        #FBFAF8;
  --paper-2:      #F2F0EB;
  --paper-3:      #E9E6DF;
  --ink:          #16181C;
  --ink-2:        #4A4F58;
  --ink-3:        #767C86;
  --navy:         #1D4E89;
  --navy-deep:    #133761;
  --navy-wash:    #EDF1F7;
  --accent:       #9B2226;
  --line:         #DCD8D0;
  --line-strong:  #BFB9AD;
  --footer-bg:    #14171C;
  --footer-ink:   #D8D5CE;
  --footer-line:  #2C3138;

  --serif: "Source Serif 4", Georgia, "Times New Roman", Times, serif;
  --sans: Inter, -apple-system, BlinkMacSystemFont, "Segoe UI", Helvetica, Arial, sans-serif;
  --mono: ui-monospace, "SF Mono", SFMono-Regular, Menlo, Consolas, monospace;

  --wrap: 1140px;
  --gutter: clamp(1.25rem, 4vw, 2.75rem);
  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root {
    --paper:        #0E1116;
    --paper-2:      #151A21;
    --paper-3:      #1D232C;
    --ink:          #E9E7E2;
    --ink-2:        #A7ADB6;
    --ink-3:        #7C838D;
    --navy:         #82ACDE;
    --navy-deep:    #A8C6EB;
    --navy-wash:    #16202D;
    --accent:       #E0727A;
    --line:         #262C35;
    --line-strong:  #39424E;
    --footer-bg:    #090C10;
    --footer-ink:   #B6BCC4;
    --footer-line:  #1E242C;
    color-scheme: dark;
  }
}

*, *::before, *::after { box-sizing: border-box; }

html { -webkit-text-size-adjust: 100%; }

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--serif);
  font-size: 17px;
  line-height: 1.6;
  font-synthesis-weight: none;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  display: flex;
  flex-direction: column;
  min-height: 100vh;
}

main { flex: 1 0 auto; }

a { color: var(--navy); text-decoration-thickness: 1px; text-underline-offset: 0.18em; }
a:hover { color: var(--navy-deep); }

:focus-visible { outline: 2px solid var(--navy); outline-offset: 3px; border-radius: 1px; }

img, svg { max-width: 100%; }
hr { border: 0; border-top: 1px solid var(--line); margin: 2.5rem 0; }

.wrap { max-width: var(--wrap); margin-inline: auto; padding-inline: var(--gutter); }
.sr-only, .skip:not(:focus) {
  position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; border: 0;
}
.skip:focus {
  position: absolute; z-index: 50; top: 0.5rem; left: 0.5rem;
  background: var(--navy); color: #fff; padding: 0.6rem 1rem;
  font-family: var(--sans); font-size: 0.85rem; text-decoration: none;
}
.tabular { font-variant-numeric: tabular-nums; }

/* ------------------------------------------------------------- masthead -- */

.masthead {
  border-bottom: 1px solid var(--line);
  background: var(--paper);
  position: relative;
}
.masthead::before {
  content: ""; display: block; height: 3px;
  background: linear-gradient(to right, var(--accent) 0 5.5rem, var(--navy) 5.5rem 100%);
}
.masthead__inner {
  display: flex; align-items: center; justify-content: space-between;
  gap: 1.5rem; padding-block: 1.15rem;
}

.wordmark { display: flex; align-items: center; gap: 0.7rem; text-decoration: none; color: var(--ink); }
.wordmark .mark { width: 30px; height: 30px; flex: none; color: var(--navy); }
.wordmark__text { display: flex; flex-direction: column; gap: 1px; }
.wordmark__name {
  font-family: var(--serif); font-weight: 600; font-size: 1.2rem;
  letter-spacing: 0.01em; line-height: 1.1;
}
.wordmark__tag {
  font-family: var(--sans); font-size: 0.6rem; font-weight: 500;
  letter-spacing: 0.16em; text-transform: uppercase; color: var(--ink-3);
}

.nav { display: flex; gap: clamp(0.9rem, 2.5vw, 1.9rem); font-family: var(--sans); font-size: 0.85rem; }
.nav a {
  color: var(--ink-2); text-decoration: none; font-weight: 500;
  padding-block: 0.25rem; border-bottom: 2px solid transparent;
}
.nav a:hover { color: var(--ink); border-bottom-color: var(--line-strong); }
.nav a[aria-current="page"] { color: var(--ink); border-bottom-color: var(--navy); }

/* ------------------------------------------------------------- primitives */

.eyebrow {
  font-family: var(--sans); font-size: 0.675rem; font-weight: 600;
  letter-spacing: 0.16em; text-transform: uppercase; color: var(--navy);
  margin: 0 0 1rem;
}

.btn {
  display: inline-flex; align-items: baseline; gap: 0.45rem;
  font-family: var(--sans); font-size: 0.82rem; font-weight: 600; line-height: 1;
  padding: 0.72rem 1.15rem; border: 1px solid var(--line-strong);
  color: var(--ink); background: transparent; text-decoration: none;
  cursor: pointer; transition: border-color 0.12s, color 0.12s, background 0.12s;
}
.btn:hover { border-color: var(--navy); color: var(--navy); }
.btn--primary { background: var(--navy); border-color: var(--navy); color: #fff; }
.btn--primary:hover { background: var(--navy-deep); border-color: var(--navy-deep); color: #fff; }
.btn--ghost { border-color: transparent; padding-inline: 0.4rem; color: var(--ink-2); }
.btn--ghost:hover { border-color: transparent; text-decoration: underline; }
.btn--block { display: flex; width: 100%; justify-content: center; margin-top: 0.5rem; }
.btn--small { font-size: 0.75rem; padding: 0.55rem 0.9rem; }
.btn__hint { font-weight: 400; font-size: 0.72rem; opacity: 0.72; }

.pills { display: flex; flex-wrap: wrap; gap: 0.4rem; list-style: none; padding: 0; margin: 1rem 0 0; }
.pill {
  display: inline-block; font-family: var(--sans); font-size: 0.66rem; font-weight: 500;
  letter-spacing: 0.09em; text-transform: uppercase; color: var(--ink-2);
  border: 1px solid var(--line); padding: 0.3rem 0.55rem; text-decoration: none;
  white-space: nowrap;
}
a.pill:hover { border-color: var(--navy); color: var(--navy); }

.ref {
  font-family: var(--sans); font-size: 0.72rem; font-weight: 600;
  letter-spacing: 0.09em; color: var(--navy); font-variant-numeric: tabular-nums;
}

.sec-head { display: flex; align-items: center; gap: 1rem; margin-bottom: 0.5rem; }
.sec-head__h {
  font-family: var(--sans); font-size: 0.7rem; font-weight: 600;
  letter-spacing: 0.16em; text-transform: uppercase; color: var(--ink-2); margin: 0;
}
.sec-head__rule { flex: 1; height: 1px; background: var(--line); }
.sec-head__more {
  font-family: var(--sans); font-size: 0.75rem; font-weight: 500;
  text-decoration: none; white-space: nowrap;
}
.sec-head__more:hover { text-decoration: underline; }

.crumbs {
  font-family: var(--sans); font-size: 0.74rem; color: var(--ink-3);
  display: flex; gap: 0.5rem; flex-wrap: wrap; margin-bottom: 1.5rem;
}
.crumbs a { color: var(--ink-3); text-decoration: none; }
.crumbs a:hover { color: var(--navy); text-decoration: underline; }

.band { padding-block: clamp(2.5rem, 5vw, 4rem); }
.band--tint { background: var(--paper-2); border-top: 1px solid var(--line); }
.band--feature { border-top: 1px solid var(--line); }

/* -------------------------------------------------------------- home hero */

.hero__inner { padding-block: clamp(3rem, 8vw, 5.5rem) clamp(2.5rem, 5vw, 4rem); }
.hero__title {
  font-family: var(--serif); font-weight: 600;
  font-size: clamp(2.1rem, 5.4vw, 3.6rem); line-height: 1.06;
  letter-spacing: -0.021em; margin: 0 0 1.4rem; max-width: 19ch;
  text-wrap: balance;
}
.hero__lede {
  font-size: clamp(1.05rem, 1.6vw, 1.22rem); line-height: 1.62;
  color: var(--ink-2); max-width: 62ch; margin: 0 0 2rem;
}
.hero__actions { display: flex; flex-wrap: wrap; gap: 0.7rem; margin: 0; }

/* ---------------------------------------------------------------- feature */

.feature { padding-top: 1.6rem; }
.feature__meta,
.entry__meta {
  display: flex; flex-wrap: wrap; align-items: baseline; gap: 0.35rem 1rem;
  font-family: var(--sans); font-size: 0.72rem; color: var(--ink-3);
  font-variant-numeric: tabular-nums;
}
.feature__meta { margin-bottom: 0.9rem; }
.feature__title {
  font-family: var(--serif); font-weight: 600;
  font-size: clamp(1.6rem, 3.4vw, 2.35rem); line-height: 1.14;
  letter-spacing: -0.014em; margin: 0 0 0.9rem; max-width: 26ch;
  text-wrap: balance;
}
.feature__title a { color: var(--ink); text-decoration: none; }
.feature__title a:hover { color: var(--navy); text-decoration: underline; text-decoration-thickness: 1px; }
.feature__dek {
  font-size: 1.1rem; line-height: 1.55; color: var(--ink-2);
  max-width: 66ch; margin: 0 0 1.1rem;
}
.feature__abstract {
  font-size: 0.95rem; line-height: 1.7; color: var(--ink-2);
  max-width: 72ch; margin: 0 0 1.5rem;
  padding-left: 1.1rem; border-left: 2px solid var(--line-strong);
}
.feature__actions { display: flex; flex-wrap: wrap; gap: 0.7rem; margin: 0; }
.feature .pills { margin-top: 1.4rem; }

/* --------------------------------------------------------------- entries  */

.entries { margin-top: 0.5rem; }
.entry {
  display: grid; grid-template-columns: 11.5rem minmax(0, 1fr);
  gap: 0 2.5rem; padding-block: 1.7rem;
  border-top: 1px solid var(--line);
}
.entry:last-child { border-bottom: 1px solid var(--line); }
.entry__meta { flex-direction: column; gap: 0.3rem; padding-top: 0.28rem; }
.entry__title {
  font-family: var(--serif); font-weight: 600; font-size: 1.32rem;
  line-height: 1.25; letter-spacing: -0.008em; margin: 0 0 0.5rem; max-width: 34ch;
}
.entry__title a { color: var(--ink); text-decoration: none; }
.entry__title a:hover { color: var(--navy); text-decoration: underline; text-decoration-thickness: 1px; }
.entry__dek { font-size: 0.96rem; line-height: 1.6; color: var(--ink-2); margin: 0; max-width: 70ch; }
.entries--compact .entry { padding-block: 1.25rem; }
.entries--compact .entry__title { font-size: 1.12rem; }
.entries--compact .pills { display: none; }

@media (max-width: 720px) {
  .entry { grid-template-columns: 1fr; gap: 0.7rem; }
  .entry__meta { flex-direction: row; padding-top: 0; }
}

.empty { font-family: var(--sans); font-size: 0.9rem; color: var(--ink-3); padding-block: 2.5rem; }

/* --------------------------------------------------------------- filters  */

.filters {
  display: flex; flex-direction: column; gap: 1rem;
  padding-bottom: 1.5rem;
}
.filters__search input {
  width: 100%; max-width: 26rem; font-family: var(--sans); font-size: 0.9rem;
  padding: 0.65rem 0.85rem; border: 1px solid var(--line-strong);
  background: var(--paper); color: var(--ink);
}
.filters__search input::placeholder { color: var(--ink-3); }
.filters__search input:focus-visible { border-color: var(--navy); }
.filters__topics { display: flex; flex-wrap: wrap; gap: 0.4rem; }
.chip {
  font-family: var(--sans); font-size: 0.7rem; font-weight: 500;
  letter-spacing: 0.06em; text-transform: uppercase;
  padding: 0.4rem 0.7rem; border: 1px solid var(--line);
  background: transparent; color: var(--ink-2); cursor: pointer;
}
.chip:hover { border-color: var(--line-strong); color: var(--ink); }
.chip.is-active { background: var(--navy); border-color: var(--navy); color: #fff; }
.filters__count { font-family: var(--sans); font-size: 0.78rem; color: var(--ink-3); margin: 0 0 0.5rem; }

/* ------------------------------------------------------------- page heads */

.pagehead { padding-block: clamp(2.5rem, 6vw, 4rem) clamp(1.5rem, 3vw, 2.25rem); }
.pagehead__title {
  font-family: var(--serif); font-weight: 600;
  font-size: clamp(2rem, 4.6vw, 3rem); line-height: 1.1;
  letter-spacing: -0.018em; margin: 0 0 1rem; max-width: 22ch;
}
.pagehead__lede { font-size: 1.06rem; line-height: 1.62; color: var(--ink-2); max-width: 62ch; margin: 0; }

/* ------------------------------------------------------------ topic grid  */

.topicgrid {
  list-style: none; padding: 0; margin: 1.5rem 0 0;
  display: grid; gap: 1px; background: var(--line);
  grid-template-columns: repeat(auto-fill, minmax(15rem, 1fr));
  border: 1px solid var(--line);
}
.topicgrid a {
  display: flex; flex-direction: column; gap: 0.35rem; justify-content: space-between;
  background: var(--paper); padding: 1.15rem 1.25rem; min-height: 5.4rem;
  text-decoration: none; color: var(--ink); transition: background 0.12s;
}
.band--tint .topicgrid a { background: var(--paper); }
.topicgrid a:hover { background: var(--navy-wash); }
.topicgrid__name { font-family: var(--serif); font-weight: 600; font-size: 1.05rem; line-height: 1.25; }
.topicgrid__n {
  font-family: var(--sans); font-size: 0.68rem; font-weight: 500;
  letter-spacing: 0.09em; text-transform: uppercase; color: var(--ink-3);
}
.topicgrid--lg a { min-height: 7rem; }

/* ---------------------------------------------------------------- paper   */

.paper__top {
  background: var(--paper-2);
  border-bottom: 1px solid var(--line);
  padding-block: clamp(2rem, 4.5vw, 3.25rem) clamp(1.75rem, 4vw, 2.75rem);
}
.paper__title {
  font-family: var(--serif); font-weight: 600;
  font-size: clamp(1.85rem, 4.3vw, 2.9rem); line-height: 1.1;
  letter-spacing: -0.019em; margin: 0 0 1.1rem; max-width: 24ch;
  text-wrap: balance;
}
.paper__dek {
  font-size: clamp(1.02rem, 1.5vw, 1.16rem); line-height: 1.58;
  color: var(--ink-2); max-width: 64ch; margin: 0 0 1.35rem;
}
.paper__byline {
  font-family: var(--sans); font-size: 0.8rem; color: var(--ink-2);
  display: flex; flex-wrap: wrap; gap: 0.5rem; align-items: baseline; margin: 0 0 1.6rem;
}
.paper__author { font-weight: 600; color: var(--ink); }
.paper__sep { color: var(--ink-3); }
.paper__actions { display: flex; flex-wrap: wrap; gap: 0.7rem; align-items: center; margin: 0; }

.paper__grid {
  display: grid; grid-template-columns: minmax(0, 1fr) 20rem;
  gap: clamp(2rem, 5vw, 4rem);
  padding-block: clamp(2.25rem, 5vw, 3.5rem) clamp(3rem, 6vw, 4.5rem);
}
@media (max-width: 940px) { .paper__grid { grid-template-columns: 1fr; } }

.sect { margin-bottom: 2.75rem; }
.sect:last-child { margin-bottom: 0; }
.sect__h {
  font-family: var(--sans); font-size: 0.7rem; font-weight: 600;
  letter-spacing: 0.16em; text-transform: uppercase; color: var(--navy);
  margin: 0 0 1.1rem; padding-bottom: 0.6rem; border-bottom: 1px solid var(--line);
}

.prose { max-width: 74ch; }
.prose p { margin: 0 0 1.1rem; }
.prose p:last-child { margin-bottom: 0; }
.prose--abstract p { font-size: 1.02rem; line-height: 1.72; }
.prose--small p { font-size: 0.9rem; line-height: 1.68; color: var(--ink-2); }
@media (min-width: 760px) {
  .prose--abstract p { text-align: justify; hyphens: auto; }
}

.findings { list-style: none; counter-reset: f; padding: 0; margin: 0; max-width: 74ch; }
.findings li {
  counter-increment: f; position: relative; padding-left: 2.4rem;
  margin-bottom: 1rem; font-size: 0.985rem; line-height: 1.65;
}
.findings li::before {
  content: counter(f, decimal-leading-zero);
  position: absolute; left: 0; top: 0.16em;
  font-family: var(--sans); font-size: 0.72rem; font-weight: 700;
  color: var(--navy); font-variant-numeric: tabular-nums;
  letter-spacing: 0.04em;
}
.findings li:last-child { margin-bottom: 0; }

.toc { list-style: none; counter-reset: t; padding: 0; margin: 0; max-width: 60ch; }
.toc li {
  counter-increment: t; display: flex; gap: 1rem; align-items: baseline;
  padding: 0.55rem 0; border-bottom: 1px dotted var(--line);
  font-size: 0.955rem; line-height: 1.4;
}
.toc li::before {
  content: counter(t); flex: none; width: 1.6rem;
  font-family: var(--sans); font-size: 0.72rem; font-weight: 600;
  color: var(--ink-3); font-variant-numeric: tabular-nums;
}
.toc .toc__end { color: var(--ink-2); border-bottom: 0; }
.toc .toc__end::before { content: "—"; }

.pdfframe {
  border: 1px solid var(--line-strong); background: var(--paper-2);
  aspect-ratio: 17 / 22; max-height: 85vh; overflow: hidden;
}
.pdfframe iframe, .pdfframe object { width: 100%; height: 100%; border: 0; display: block; }
.pdfframe__fallback { font-family: var(--sans); font-size: 0.78rem; color: var(--ink-3); margin: 0.7rem 0 0; }

/* ------------------------------------------------------------------ rail  */

.rail { display: flex; flex-direction: column; gap: 1.25rem; min-width: 0; }
.railcard { border: 1px solid var(--line); padding: 1.15rem 1.25rem; background: var(--paper); }
.railcard--dl { border-top: 3px solid var(--navy); background: var(--paper-2); }
.railcard__h {
  font-family: var(--sans); font-size: 0.68rem; font-weight: 600;
  letter-spacing: 0.15em; text-transform: uppercase; color: var(--ink-2);
  margin: 0 0 0.85rem;
}
.railcard__spec {
  font-family: var(--sans); font-size: 0.78rem; color: var(--ink-3);
  margin: -0.4rem 0 0.9rem; font-variant-numeric: tabular-nums;
}
.railcard__note { font-family: var(--sans); font-size: 0.72rem; line-height: 1.5; color: var(--ink-3); margin: 0.85rem 0 0; }

.deflist { display: grid; grid-template-columns: 6.5rem minmax(0, 1fr); margin: 0; font-size: 0.82rem; }
.deflist dt {
  grid-column: 1; font-family: var(--sans); font-size: 0.66rem; font-weight: 600;
  letter-spacing: 0.08em; text-transform: uppercase; color: var(--ink-3);
  padding: 0.5rem 0.6rem 0.5rem 0; border-top: 1px solid var(--line);
}
.deflist dd {
  grid-column: 2; margin: 0; padding: 0.5rem 0; color: var(--ink);
  border-top: 1px solid var(--line); line-height: 1.45;
}
.deflist dt:first-of-type, .deflist dd:first-of-type { border-top: 0; padding-top: 0; }

.keywords { list-style: none; padding: 0; margin: 0; font-family: var(--sans); font-size: 0.74rem; line-height: 1.5; color: var(--ink-2); }
.keywords li { display: inline; }
.keywords li:not(:last-child)::after { content: " · "; color: var(--ink-3); }

.cite__tabs { display: flex; gap: 0.25rem; margin-bottom: 0.7rem; border-bottom: 1px solid var(--line); }
.cite__tab {
  font-family: var(--sans); font-size: 0.7rem; font-weight: 600; letter-spacing: 0.05em;
  padding: 0.4rem 0.6rem; border: 0; border-bottom: 2px solid transparent;
  background: transparent; color: var(--ink-3); cursor: pointer;
}
.cite__tab:hover { color: var(--ink); }
.cite__tab.is-active { color: var(--navy); border-bottom-color: var(--navy); }
.cite__body {
  font-family: var(--mono); font-size: 0.7rem; line-height: 1.55; color: var(--ink-2);
  background: var(--paper-2); border: 1px solid var(--line);
  padding: 0.75rem 0.85rem; margin: 0; max-height: 15rem; overflow: auto;
  white-space: pre-wrap; overflow-wrap: anywhere;
}
.railcard .cite__body { background: var(--paper-3); }

/* ----------------------------------------------------------- about prose  */

.prose--page { max-width: 66ch; }
.prose--page h2 {
  font-family: var(--sans); font-size: 0.72rem; font-weight: 600;
  letter-spacing: 0.16em; text-transform: uppercase; color: var(--navy);
  margin: 2.5rem 0 0.9rem;
}
.prose--page p { font-size: 1rem; line-height: 1.72; margin: 0 0 1.15rem; }
.prose__lede { font-size: 1.18rem !important; line-height: 1.6 !important; color: var(--ink-2); }
.prose__meta { font-family: var(--sans); font-size: 0.8rem; color: var(--ink-3); }
.rule { margin: 2.5rem 0 1.5rem; }

/* ---------------------------------------------------------------- footer  */

.footer {
  background: var(--footer-bg); color: var(--footer-ink);
  font-family: var(--sans);
}
.footer__inner {
  display: flex; flex-wrap: wrap; gap: 2.5rem 4rem; justify-content: space-between;
  padding-block: clamp(2.5rem, 5vw, 3.5rem);
}
.footer__brand { max-width: 30rem; }
.footer__name { font-family: var(--serif); font-size: 1.25rem; font-weight: 600; color: #fff; margin: 0; }
.footer__tag {
  font-size: 0.62rem; font-weight: 500; letter-spacing: 0.16em;
  text-transform: uppercase; color: var(--ink-3); margin: 0.3rem 0 1rem;
}
.footer__note { font-size: 0.86rem; line-height: 1.6; color: var(--footer-ink); margin: 0; opacity: 0.82; }
.footer__cols { display: flex; gap: 3.5rem; flex-wrap: wrap; }
.footer__cols > div { display: flex; flex-direction: column; gap: 0.55rem; }
.footer__h {
  font-size: 0.64rem; font-weight: 600; letter-spacing: 0.16em;
  text-transform: uppercase; color: var(--ink-3); margin: 0 0 0.2rem;
}
.footer__cols a { color: var(--footer-ink); text-decoration: none; font-size: 0.86rem; }
.footer__cols a:hover { color: #fff; text-decoration: underline; }
.footer__legal {
  display: flex; flex-wrap: wrap; gap: 0.5rem 2rem; justify-content: space-between;
  padding-block: 1.15rem; border-top: 1px solid var(--footer-line);
  font-size: 0.75rem; color: var(--ink-3);
}
.footer__legal p { margin: 0; }
.footer__legal a { color: var(--ink-3); }
.footer__legal a:hover { color: #fff; }

/* ----------------------------------------------------------------- print  */

@media print {
  .masthead, .footer, .paper__actions, .rail, .filters, .skip { display: none !important; }
  body { font-size: 11pt; background: #fff; color: #000; }
  .paper__grid { display: block; }
  a { color: #000; text-decoration: none; }
}

/* Filtering: an explicit class rule is required because .entry sets display:grid. */
.entry[hidden] { display: none; }
.entry.is-last { border-bottom: 1px solid var(--line); }

/* Page heads already carry their own bottom space. */
.pagehead + .band { padding-top: 0; }

/* The tagline wraps to two lines below ~420px and unbalances the masthead. */
@media (max-width: 460px) {
  .wordmark__tag { display: none; }
  .wordmark__name { font-size: 1.1rem; }
  .nav { font-size: 0.8rem; }
}