/* =============================================================================
   Fan Zhu — personal site
   Palette: deep navy with a steel-blue accent, contrast-validated.
   All ink/accent/ramp pairs clear WCAG AA (>=4.5:1) against their own surface.
   ========================================================================== */

/* ---------- Tokens ------------------------------------------------------- */

:root {
  color-scheme: dark;

  --page:        #080e18;
  --surface:     #0d1523;
  --surface-2:   #121d2e;
  --surface-3:   #1a273a;

  --ink:         #e8eef7;  /* 16.57:1 */
  --ink-2:       #a7b8ce;  /*  9.56:1 */
  --muted:       #7f92a9;  /*  6.06:1 */

  --accent:      #7dabdd;  /*  8.05:1 */
  --accent-hi:   #a7c8ee;  /* 11.17:1 */
  --accent-dim:  rgba(125, 171, 221, 0.14);
  /* Second tone of the same hue: the receded one, always less present than
     --accent in either theme — dimmer here, lighter in the light theme — so a
     heading can move from a past role to a current one and read as a
     direction. */
  --accent-2:    #628ab8;  /*  5.38:1 */

  --bull:        #46bf94;  /*  8.41:1 */
  --bear:        #e5776c;  /*  6.62:1 */

  /* Sequential ramp, one hue, low -> high = deep navy -> luminous blue */
  --r1: #0f1e33;
  --r2: #16304f;
  --r3: #1c4470;
  --r4: #235c92;
  --r5: #4d8bc4;
  --r6: #7fb0dd;
  --r7: #b0d2f0;
  /* Ink to place ON each ramp step (crossover after r4) */
  --r-ink-lo: #e8eef7;
  --r-ink-hi: #080e18;

  --line:        rgba(232, 238, 247, 0.10);
  --line-2:      rgba(232, 238, 247, 0.16);
  --glow:        rgba(125, 171, 221, 0.10);

  --font-display: "Libre Franklin", "Franklin Gothic Medium", "Helvetica Neue", Arial, sans-serif;
  --font-body: "Inter", system-ui, -apple-system, "Segoe UI", Arial, sans-serif;
  --font-mono: "IBM Plex Mono", ui-monospace, "SF Mono", Menlo, Consolas, monospace;

  --maxw: 1140px;
  --gutter: clamp(1.25rem, 5vw, 4rem);
  --radius: 4px;
  --ease: cubic-bezier(0.22, 0.61, 0.36, 1);
}

@media (prefers-color-scheme: light) {
  :root:not([data-theme="dark"]) {
    color-scheme: light;
    --page:      #f5f8fc;
    --surface:   #ffffff;
    --surface-2: #eaf0f8;
    --surface-3: #dde6f2;
    --ink:       #0d1826;  /* 16.77:1 */
    --ink-2:     #46586e;  /*  6.84:1 */
    --muted:     #56687e;  /*  5.36:1 */
    --accent:    #17548f;  /*  7.30:1 */
    --accent-hi: #0d3b68;  /* 10.70:1 */
    --accent-dim: rgba(23, 84, 143, 0.10);
    --accent-2:  #2b6cb0;  /*  5.09:1 */
    --bull:      #0f6b46;  /*  6.14:1 */
    --bear:      #a8321f;  /*  6.28:1 */
    --r1: #eef4fb; --r2: #d4e4f4; --r3: #a9c8e8; --r4: #71a3d3;
    --r5: #2f6699; --r6: #1c4f80; --r7: #0e3357;
    --r-ink-lo: #0d1826;
    --r-ink-hi: #ffffff;
    --line:   rgba(13, 24, 38, 0.12);
    --line-2: rgba(13, 24, 38, 0.20);
    --glow:   rgba(23, 84, 143, 0.07);
  }
}

:root[data-theme="light"] {
  color-scheme: light;
  --page:      #f5f8fc;
  --surface:   #ffffff;
  --surface-2: #eaf0f8;
  --surface-3: #dde6f2;
  --ink:       #0d1826;
  --ink-2:     #46586e;
  --muted:     #56687e;
  --accent:    #17548f;
  --accent-hi: #0d3b68;
  --accent-dim: rgba(23, 84, 143, 0.10);
  --accent-2:  #2b6cb0;
  --bull:      #0f6b46;
  --bear:      #a8321f;
  --r1: #eef4fb; --r2: #d4e4f4; --r3: #a9c8e8; --r4: #71a3d3;
  --r5: #2f6699; --r6: #1c4f80; --r7: #0e3357;
  --r-ink-lo: #0d1826;
  --r-ink-hi: #ffffff;
  --line:   rgba(13, 24, 38, 0.12);
  --line-2: rgba(13, 24, 38, 0.20);
  --glow:   rgba(23, 84, 143, 0.07);
}

/* ---------- Base --------------------------------------------------------- */

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

html {
  scroll-behavior: smooth;
  scroll-padding-top: 5rem;
  -webkit-text-size-adjust: 100%;
}
@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
}

body {
  margin: 0;
  background: var(--page);
  color: var(--ink);
  font-family: var(--font-body);
  font-size: 16px;
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
  overflow-x: hidden;
}

img { max-width: 100%; display: block; }

a {
  color: var(--accent);
  text-decoration: none;
  transition: color 0.2s var(--ease);
}
a:hover { color: var(--accent-hi); }

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

::selection { background: var(--accent); color: var(--page); }

.wrap {
  width: 100%;
  max-width: var(--maxw);
  margin-inline: auto;
  padding-inline: var(--gutter);
}

.skip {
  position: absolute;
  left: -9999px;
  top: 0;
  background: var(--accent);
  color: var(--page);
  padding: 0.75rem 1.25rem;
  z-index: 200;
  font-family: var(--font-mono);
  font-size: 0.8rem;
}
.skip:focus { left: 0; }

.visually-hidden {
  position: absolute;
  width: 1px; height: 1px;
  padding: 0; margin: -1px;
  overflow: hidden;
  clip: rect(0 0 0 0);
  clip-path: inset(50%);
  white-space: nowrap;
  border: 0;
}

/* ---------- Type --------------------------------------------------------- */

h1, h2, h3, h4 {
  font-family: var(--font-display);
  font-weight: 600;
  line-height: 1.14;
  letter-spacing: -0.021em;
  margin: 0;
}

.mono {
  font-family: var(--font-mono);
  font-size: 0.75rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  font-weight: 500;
}

.eyebrow {
  font-family: var(--font-mono);
  font-size: 0.73rem;
  font-weight: 500;
  letter-spacing: 0.18em;
  text-transform: uppercase;
  color: var(--accent);
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-bottom: 1.5rem;
}
.eyebrow::after {
  content: "";
  height: 1px;
  flex: 1;
  background: linear-gradient(90deg, var(--line-2), transparent);
}

/* Section and card numbers are generated rather than typed, so inserting,
   removing or reordering a section never means renumbering the rest by hand.
   Opt in with `data-auto`; an eyebrow or card label with its own text
   (e.g. "Method", "/ MAY 2022") simply leaves the attribute off. */
main { counter-reset: section; }
.eyebrow[data-auto] { counter-increment: section; }
.eyebrow[data-auto]::before { content: counter(section, decimal-leading-zero) " \2014"; }

.grid-2, .grid-3 { counter-reset: card; }
.card__num[data-auto] { counter-increment: card; }
.card__num[data-auto]::before { content: "/ " counter(card, decimal-leading-zero); }

.lede {
  font-size: clamp(1rem, 1.4vw, 1.12rem);
  color: var(--ink-2);
  line-height: 1.7;
  max-width: 68ch;
}

/* ---------- Nav ---------------------------------------------------------- */

.nav {
  position: fixed;
  inset: 0 0 auto 0;
  z-index: 100;
  height: 4.5rem;
  display: flex;
  align-items: center;
  transition: background 0.3s var(--ease), border-color 0.3s var(--ease),
              backdrop-filter 0.3s var(--ease);
  border-bottom: 1px solid transparent;
}
.nav.is-stuck {
  background: color-mix(in srgb, var(--page) 82%, transparent);
  backdrop-filter: blur(14px) saturate(140%);
  -webkit-backdrop-filter: blur(14px) saturate(140%);
  border-bottom-color: var(--line);
}
.nav__inner {
  width: 100%;
  max-width: var(--maxw);
  margin-inline: auto;
  padding-inline: var(--gutter);
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 1rem;
}
.brand {
  font-family: var(--font-mono);
  font-size: 0.85rem;
  font-weight: 700;
  letter-spacing: 0.08em;
  color: var(--ink);
  display: inline-flex;
  align-items: center;
  gap: 0.55rem;
}
.brand__mark {
  width: 1.6rem; height: 1.6rem;
  display: grid; place-items: center;
  border: 1px solid var(--accent);
  color: var(--accent);
  font-size: 0.66rem;
  border-radius: 3px;
}
.brand:hover { color: var(--ink); }

.nav__links {
  display: flex;
  align-items: center;
  gap: 1.75rem;
  list-style: none;
  margin: 0; padding: 0;
}
.nav__links a {
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.11em;
  text-transform: uppercase;
  color: var(--muted);
  position: relative;
  padding-block: 0.4rem;
}
.nav__links a::after {
  content: "";
  position: absolute;
  left: 0; bottom: 0;
  height: 1px; width: 0;
  background: var(--accent);
  transition: width 0.25s var(--ease);
}
.nav__links a:hover,
.nav__links a[aria-current="true"] { color: var(--ink); }
.nav__links a:hover::after,
.nav__links a[aria-current="true"]::after { width: 100%; }

.nav__actions { display: flex; align-items: center; gap: 0.5rem; }

.icon-btn {
  width: 2.2rem; height: 2.2rem;
  display: grid; place-items: center;
  background: transparent;
  border: 1px solid var(--line);
  border-radius: var(--radius);
  color: var(--ink-2);
  cursor: pointer;
  transition: all 0.2s var(--ease);
  padding: 0;
}
.icon-btn:hover {
  color: var(--accent);
  border-color: var(--accent);
  background: var(--accent-dim);
}
.icon-btn svg { width: 1rem; height: 1rem; }
:root:not([data-theme="light"]) .icon-sun { display: none; }
:root[data-theme="light"] .icon-moon { display: none; }
@media (prefers-color-scheme: light) {
  :root:not([data-theme="dark"]) .icon-moon { display: none; }
  :root:not([data-theme="dark"]) .icon-sun { display: block; }
}
:root[data-theme="dark"] .icon-sun { display: none; }
:root[data-theme="dark"] .icon-moon { display: block; }

.nav__toggle { display: none; }

@media (max-width: 860px) {
  .nav__toggle { display: grid; }
  .nav__links {
    position: fixed;
    inset: 4.5rem 0 auto 0;
    flex-direction: column;
    align-items: flex-start;
    gap: 0;
    background: var(--surface);
    border-bottom: 1px solid var(--line);
    padding: 0.5rem var(--gutter) 1.5rem;
    transform: translateY(-140%);
    transition: transform 0.32s var(--ease);
  }
  .nav__links.is-open { transform: translateY(0); }
  .nav__links li { width: 100%; border-bottom: 1px solid var(--line); }
  .nav__links a { display: block; padding: 1rem 0; font-size: 0.8rem; }
}

/* ---------- Hero --------------------------------------------------------- */

.hero {
  position: relative;
  min-height: 100svh;
  display: flex;
  align-items: center;
  padding-block: 8rem 4rem;
  overflow: hidden;
}
#network {
  position: absolute;
  inset: 0;
  width: 100%;
  height: 100%;
  z-index: 0;
}
.hero::after {
  /* keeps the network from competing with the text column */
  content: "";
  position: absolute;
  inset: 0;
  z-index: 1;
  background:
    radial-gradient(90ch 60ch at 12% 45%, var(--page) 12%,
                    color-mix(in srgb, var(--page) 72%, transparent) 46%, transparent 74%),
    linear-gradient(180deg, transparent 62%, var(--page) 100%);
  pointer-events: none;
}
.hero__inner { position: relative; z-index: 2; width: 100%; }

.hero__eyebrow {
  font-family: var(--font-mono);
  font-size: clamp(0.66rem, 1.4vw, 0.75rem);
  letter-spacing: 0.16em;
  color: var(--accent);
  margin-bottom: 1.75rem;
  display: flex;
  flex-wrap: wrap;
  align-items: center;
  gap: 0.5rem 0.85rem;
}
.hero__eyebrow .dot { color: var(--muted); }

h1.hero__name {
  font-size: clamp(2.85rem, 7vw, 4.8rem);
  font-weight: 300;
  line-height: 1.02;
  letter-spacing: -0.032em;
  margin-bottom: 1.5rem;
}
h1.hero__name em {
  font-style: normal;
  font-weight: 700;
  color: inherit;
}

.hero__sub {
  font-size: clamp(1.02rem, 1.7vw, 1.22rem);
  line-height: 1.62;
  color: var(--ink-2);
  max-width: 58ch;
  margin: 0 0 2.5rem;
}
.hero__sub strong { color: var(--ink); font-weight: 600; }

.hero__cta { display: flex; flex-wrap: wrap; gap: 0.85rem; margin-bottom: 4rem; }

.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  font-family: var(--font-mono);
  font-size: 0.75rem;
  letter-spacing: 0.11em;
  text-transform: uppercase;
  padding: 0.9rem 1.5rem;
  border-radius: var(--radius);
  border: 1px solid var(--accent);
  transition: all 0.22s var(--ease);
  cursor: pointer;
}
.btn--primary {
  background: var(--accent);
  color: var(--page);
  font-weight: 600;
}
.btn--primary:hover {
  background: var(--accent-hi);
  border-color: var(--accent-hi);
  color: var(--page);
  transform: translateY(-2px);
}
.btn--ghost { background: transparent; color: var(--accent); }
.btn--ghost:hover {
  background: var(--accent-dim);
  transform: translateY(-2px);
  color: var(--accent-hi);
}
.btn svg { width: 0.9rem; height: 0.9rem; }

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

.stats {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(150px, 1fr));
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
}
.stat { background: var(--page); padding: 1.4rem 1.5rem; }
.hero .stat { background: color-mix(in srgb, var(--page) 88%, transparent); }
.stat__val {
  font-family: var(--font-display);
  font-size: clamp(1.5rem, 2.8vw, 1.95rem);
  font-weight: 600;
  line-height: 1.05;
  color: var(--accent);
  letter-spacing: -0.022em;
  font-variant-numeric: tabular-nums;
  margin-bottom: 0.55rem;
}
.stat__lab {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.09em;
  text-transform: uppercase;
  color: var(--muted);
  line-height: 1.5;
}

.scroll-cue {
  position: absolute;
  left: 50%; bottom: 1.75rem;
  transform: translateX(-50%);
  z-index: 2;
  font-family: var(--font-mono);
  font-size: 0.6rem;
  letter-spacing: 0.24em;
  text-transform: uppercase;
  color: var(--muted);
  display: flex;
  flex-direction: column;
  align-items: center;
  gap: 0.6rem;
}
.scroll-cue::after {
  content: "";
  width: 1px; height: 2.5rem;
  background: linear-gradient(180deg, var(--accent), transparent);
  animation: cue 2.4s var(--ease) infinite;
}
@keyframes cue {
  0%, 100% { opacity: 0.25; transform: scaleY(0.55); transform-origin: top; }
  50%      { opacity: 1;    transform: scaleY(1);    transform-origin: top; }
}
@media (max-width: 860px) { .scroll-cue { display: none; } }

/* ---------- Sections ----------------------------------------------------- */

.section { padding-block: clamp(5rem, 11vw, 9rem); position: relative; }
.section--alt { background: var(--surface); border-block: 1px solid var(--line); }

.section__head { margin-bottom: clamp(2.75rem, 6vw, 4.5rem); max-width: 72ch; }
.section__head h2 {
  font-size: clamp(1.8rem, 3.6vw, 2.55rem);
  line-height: 1.17;
  margin-bottom: 1.25rem;
}
/* Two tones of the one accent hue, so a heading can carry a direction:
   `em.lo` is the receded term, the plain `em` the current, dominant one.
   Both clear AA in either theme. */
.section__head h2 em { font-style: normal; color: var(--accent); }
.section__head h2 em.lo { color: var(--accent-2); }

/* ---------- Cards -------------------------------------------------------- */

.card {
  background: var(--surface-2);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  padding: clamp(1.5rem, 3vw, 2.25rem);
  transition: border-color 0.25s var(--ease), transform 0.25s var(--ease);
}
.section--alt .card { background: var(--page); }
.card:hover { border-color: var(--line-2); }

.grid-3 {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(258px, 1fr));
  gap: 1.25rem;
}
.grid-2 {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(320px, 1fr));
  gap: 1.25rem;
}

.card__num {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  font-weight: 500;
  letter-spacing: 0.13em;
  color: var(--accent);
  margin-bottom: 1rem;
}
.card h3 {
  font-size: 1.16rem;
  line-height: 1.32;
  margin-bottom: 0.85rem;
  letter-spacing: -0.012em;
}
.card p { color: var(--ink-2); font-size: 0.95rem; margin: 0; line-height: 1.7; }

/* ---------- Timeline ----------------------------------------------------- */

.tl { position: relative; }
.tl::before {
  content: "";
  position: absolute;
  left: 0; top: 0.7rem; bottom: 0.7rem;
  width: 1px;
  background: linear-gradient(180deg, var(--accent), var(--line) 22%, var(--line) 78%, transparent);
}
.tl__item { position: relative; padding-left: 2.5rem; padding-bottom: 2.75rem; }
.tl__item:last-child { padding-bottom: 0; }
.tl__item::before {
  content: "";
  position: absolute;
  left: -4px; top: 0.55rem;
  width: 9px; height: 9px;
  border-radius: 50%;
  background: var(--page);
  border: 1px solid var(--accent);
}
.tl__item--now::before { background: var(--accent); box-shadow: 0 0 0 4px var(--accent-dim); }

.tl__meta {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  gap: 0.4rem 1rem;
  margin-bottom: 0.35rem;
}
.tl__date {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  letter-spacing: 0.1em;
  color: var(--accent);
  text-transform: uppercase;
}
.tl__loc {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  color: var(--muted);
  letter-spacing: 0.05em;
}
.tl__role {
  font-family: var(--font-display);
  font-size: clamp(1.22rem, 2.2vw, 1.5rem);
  line-height: 1.25;
  margin-bottom: 0.3rem;
}
.tl__org {
  font-size: 0.92rem;
  color: var(--ink-2);
  margin-bottom: 0.6rem;
}
.tl__org strong { color: var(--ink); font-weight: 600; }

/* One or two lines of scope per role. The timeline is a trajectory, not a
   work history — detail lives in Research and Building. */
.tl__desc {
  color: var(--ink-2);
  font-size: 0.95rem;
  line-height: 1.7;
  margin: 0;
  max-width: 72ch;
}
.tl__desc strong { color: var(--ink); font-weight: 600; }

/* ---------- Tags --------------------------------------------------------- */

.tags { display: flex; flex-wrap: wrap; gap: 0.4rem; margin-top: 1.25rem; }
.tag {
  font-family: var(--font-mono);
  font-size: 0.66rem;
  letter-spacing: 0.06em;
  color: var(--ink-2);
  border: 1px solid var(--line);
  border-radius: 2px;
  padding: 0.3rem 0.6rem;
  background: var(--page);
  white-space: nowrap;
}
.section--alt .tag { background: var(--surface-2); }

/* ---------- Research ----------------------------------------------------- */

.paper {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface-2);
  overflow: hidden;
}
.section--alt .paper { background: var(--page); }

.paper__head {
  padding: clamp(1.75rem, 3.5vw, 2.75rem);
  border-bottom: 1px solid var(--line);
  position: relative;
}
.paper__head::before {
  content: "";
  position: absolute;
  left: 0; top: 0; bottom: 0;
  width: 2px;
  background: var(--accent);
}
.paper__venue {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--accent);
  margin-bottom: 1rem;
}
.paper__title {
  font-size: clamp(1.32rem, 2.6vw, 1.8rem);
  line-height: 1.25;
  margin-bottom: 1rem;
}
.paper__authors { font-size: 0.9rem; color: var(--muted); margin: 0 0 1.5rem; }
.paper__authors strong { color: var(--ink); font-weight: 600; }
.paper__abstract {
  color: var(--ink-2);
  font-size: 0.96rem;
  line-height: 1.78;
  margin: 0;
  max-width: 78ch;
}

.paper__link,
.entry__links {
  margin: 1.5rem 0 0;
  font-family: var(--font-mono);
  font-size: 0.72rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  display: flex;
  flex-wrap: wrap;
  gap: 0.6rem 1.5rem;
}
.paper__link a,
.entry__links a {
  display: inline-flex;
  align-items: center;
  gap: 0.5rem;
  border-bottom: 1px solid var(--line-2);
  padding-bottom: 0.2rem;
  transition: color 0.2s var(--ease), border-color 0.2s var(--ease);
}
.paper__link a:hover,
.entry__links a:hover { border-bottom-color: var(--accent-hi); }
.paper__link svg,
.entry__links svg { width: 0.85rem; height: 0.85rem; flex: none; }

/* ---------- Research entries --------------------------------------------
   The repeatable unit. Every research item other than the featured paper is
   one <article class="entry">; copy a block, change the text, done. Only
   .entry__meta and .entry__title are required.
   ---------------------------------------------------------------------- */

.entries { display: grid; gap: 1.25rem; margin-top: 1.25rem; }

.entry {
  background: var(--surface-2);
  border: 1px solid var(--line);
  border-left: 2px solid var(--accent);
  border-radius: var(--radius);
  padding: clamp(1.5rem, 3vw, 2.25rem);
  transition: border-color 0.25s var(--ease);
}
.section--alt .entry { background: var(--page); }
.entry:hover { border-color: var(--line-2); border-left-color: var(--accent); }

.entry__meta {
  font-family: var(--font-mono);
  font-size: 0.7rem;
  font-weight: 500;
  letter-spacing: 0.13em;
  text-transform: uppercase;
  color: var(--accent);
  margin: 0 0 0.9rem;
}
.entry__title {
  font-size: clamp(1.16rem, 2vw, 1.4rem);
  line-height: 1.3;
  margin: 0 0 0.6rem;
}
.entry__authors { font-size: 0.86rem; color: var(--muted); margin: 0 0 0.9rem; }
.entry__authors strong { color: var(--ink); font-weight: 600; }
.entry__desc {
  color: var(--ink-2);
  font-size: 0.95rem;
  line-height: 1.7;
  margin: 0;
  max-width: 78ch;
}

/* Inline links inside running prose get an underline so they are findable. */
.card p a,
.lede a,
.tl__desc a,
.figure__note a,
.paper__abstract a {
  text-decoration: underline;
  text-decoration-thickness: 1px;
  text-underline-offset: 0.18em;
  text-decoration-color: var(--line-2);
}
.card p a:hover,
.lede a:hover,
.tl__desc a:hover,
.figure__note a:hover,
.paper__abstract a:hover { text-decoration-color: currentColor; }

.paper__body { padding: clamp(1.75rem, 3.5vw, 2.75rem); }

.method {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(180px, 1fr));
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
  border-radius: var(--radius);
  overflow: hidden;
  margin-bottom: 2.5rem;
}
.method__step { background: var(--surface-2); padding: 1.35rem; }
.section--alt .method__step { background: var(--page); }
.method__n {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  font-weight: 500;
  color: var(--accent);
  letter-spacing: 0.11em;
  margin-bottom: 0.7rem;
}
.method__t {
  font-size: 0.94rem;
  font-weight: 600;
  color: var(--ink);
  margin-bottom: 0.4rem;
  line-height: 1.35;
}
.method__d { font-size: 0.84rem; color: var(--muted); line-height: 1.6; margin: 0; }

/* ---------- Charts ------------------------------------------------------- */

.figure {
  border: 1px solid var(--line);
  border-radius: var(--radius);
  background: var(--surface);
  padding: clamp(1.25rem, 2.5vw, 1.75rem);
}
.section--alt .figure { background: var(--surface-2); }

.figure__title {
  font-family: var(--font-display);
  font-size: 1rem;
  font-weight: 600;
  color: var(--ink);
  margin: 0 0 0.35rem;
  letter-spacing: 0;
}
.figure__sub {
  font-size: 0.82rem;
  color: var(--muted);
  margin: 0 0 1.5rem;
  line-height: 1.55;
}
.figure__note {
  font-size: 0.78rem;
  color: var(--muted);
  margin: 1.25rem 0 0;
  line-height: 1.6;
  padding-top: 1rem;
  border-top: 1px solid var(--line);
}

.figure__scroll { overflow-x: auto; }

/* Heatmap */
.hm { display: grid; gap: 2px; min-width: 460px; }
.hm__row { display: grid; grid-template-columns: 8.5rem repeat(4, 1fr); gap: 2px; }
.hm__corner,
.hm__colhead,
.hm__rowhead {
  font-family: var(--font-mono);
  font-size: 0.66rem;
  letter-spacing: 0.05em;
  color: var(--muted);
  text-transform: uppercase;
  display: flex;
  align-items: center;
  padding: 0.5rem 0.4rem;
  line-height: 1.35;
}
.hm__colhead { justify-content: center; text-align: center; }
.hm__cell {
  position: relative;
  aspect-ratio: 2.2 / 1;
  min-height: 3.4rem;
  border-radius: 2px;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.15rem;
  cursor: default;
  transition: transform 0.15s var(--ease), box-shadow 0.15s var(--ease);
}
.hm__cell:hover, .hm__cell:focus-visible {
  transform: scale(1.035);
  box-shadow: 0 0 0 2px var(--surface), 0 0 0 3px var(--accent);
  z-index: 3;
}
.hm__cell.is-best { box-shadow: 0 0 0 2px var(--surface), 0 0 0 3px var(--accent); }
.hm__v {
  font-family: var(--font-mono);
  font-size: 0.94rem;
  font-weight: 600;
  font-variant-numeric: tabular-nums;
  letter-spacing: -0.01em;
}
.hm__m { font-family: var(--font-mono); font-size: 0.62rem; opacity: 0.82; letter-spacing: 0.02em; }

.legend {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-top: 1.25rem;
  font-family: var(--font-mono);
  font-size: 0.65rem;
  color: var(--muted);
  letter-spacing: 0.06em;
  flex-wrap: wrap;
}
.legend__ramp {
  display: flex;
  height: 0.55rem;
  width: 8.5rem;
  border-radius: 2px;
  overflow: hidden;
  border: 1px solid var(--line);
}
.legend__ramp span { flex: 1; }

/* Confusion matrix */
.cm { display: grid; grid-template-columns: auto 1fr 1fr; gap: 2px; min-width: 340px; }
.cm__lab {
  font-family: var(--font-mono);
  font-size: 0.62rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
  display: flex;
  align-items: center;
  justify-content: center;
  text-align: center;
  padding: 0.5rem 0.6rem;
  line-height: 1.35;
}
.cm__cell {
  border-radius: 2px;
  padding: 1.35rem 0.75rem;
  display: flex;
  flex-direction: column;
  align-items: center;
  justify-content: center;
  gap: 0.25rem;
}
.cm__n {
  font-family: var(--font-display);
  font-size: 1.85rem;
  font-weight: 600;
  line-height: 1;
  font-variant-numeric: tabular-nums;
}
.cm__t { font-family: var(--font-mono); font-size: 0.62rem; letter-spacing: 0.07em; text-transform: uppercase; opacity: 0.85; }

/* Table view (accessibility companion to every chart) */
.tablewrap { margin-top: 1.25rem; }
.tablewrap summary {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--muted);
  cursor: pointer;
  padding: 0.5rem 0;
  list-style: none;
  display: flex;
  align-items: center;
  gap: 0.5rem;
}
.tablewrap summary::-webkit-details-marker { display: none; }
.tablewrap summary::before { content: "+"; color: var(--accent); font-size: 0.9rem; }
.tablewrap[open] summary::before { content: "−"; }
.tablewrap summary:hover { color: var(--ink); }

table.data {
  width: 100%;
  border-collapse: collapse;
  font-size: 0.82rem;
  margin-top: 0.75rem;
}
table.data th, table.data td {
  text-align: left;
  padding: 0.55rem 0.75rem;
  border-bottom: 1px solid var(--line);
  font-variant-numeric: tabular-nums;
}
table.data th {
  font-family: var(--font-mono);
  font-size: 0.64rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--muted);
  font-weight: 500;
}
table.data td { color: var(--ink-2); }
table.data td:first-child { color: var(--ink); }
table.data tr.is-best td { color: var(--accent); font-weight: 600; }

/* ---------- Toolkit ------------------------------------------------------ */

.kit { display: grid; gap: 1px; background: var(--line); border: 1px solid var(--line); border-radius: var(--radius); overflow: hidden; }
.kit__row {
  background: var(--page);
  display: grid;
  grid-template-columns: 12rem 1fr;
  gap: 1.5rem;
  padding: 1.4rem clamp(1rem, 2.5vw, 1.75rem);
  align-items: start;
}
.section--alt .kit__row { background: var(--surface); }
.kit__cat {
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--accent);
  padding-top: 0.3rem;
}
.kit__items { display: flex; flex-wrap: wrap; gap: 0.4rem; }
@media (max-width: 620px) {
  .kit__row { grid-template-columns: 1fr; gap: 0.85rem; }
}

/* ---------- Contact ------------------------------------------------------ */

.contact { text-align: center; }
.contact h2 { font-size: clamp(2.4rem, 7vw, 4.5rem); margin-bottom: 1.5rem; }
.contact .lede { margin-inline: auto; text-align: center; margin-bottom: 2.75rem; }
.contact__links {
  display: flex;
  flex-wrap: wrap;
  gap: 0.85rem;
  justify-content: center;
}

/* ---------- Footer ------------------------------------------------------- */

.footer {
  border-top: 1px solid var(--line);
  padding-block: 2.5rem;
  font-family: var(--font-mono);
  font-size: 0.68rem;
  letter-spacing: 0.06em;
  color: var(--muted);
}
.footer__inner {
  display: flex;
  flex-wrap: wrap;
  gap: 1rem;
  justify-content: space-between;
  align-items: center;
}
.footer a { color: var(--muted); }
.footer a:hover { color: var(--accent); }

/* ---------- Reveal ------------------------------------------------------- */

.reveal {
  opacity: 0;
  transform: translateY(18px);
  transition: opacity 0.7s var(--ease), transform 0.7s var(--ease);
}
.reveal.is-in { opacity: 1; transform: none; }

@media (prefers-reduced-motion: reduce) {
  .reveal { opacity: 1; transform: none; transition: none; }
  .scroll-cue::after { animation: none; }
  * { animation-duration: 0.001ms !important; transition-duration: 0.001ms !important; }
}

/* ---------- Print -------------------------------------------------------- */

@media print {
  .nav, .scroll-cue, #network, .hero::after { display: none !important; }
  body { background: #fff; color: #000; }
  .section { padding-block: 1.5rem; page-break-inside: avoid; }
}