/* ==========================================================================
   dst9.tech — Applied AI Agent Evaluation
   Stylesheet. No external requests: no font CDNs, no trackers, no remote assets.
   Single committed visual world (graphite-blue ground) per the visual brief.
   ========================================================================== */

/* --- 1. Tokens ----------------------------------------------------------- */

:root {
  /* Ground and surfaces */
  --ground:       #0A0F15;
  --ground-2:     #0D141C;
  --surface:      #121B25;
  --surface-2:    #16212C;

  /* Hairlines */
  --line:         #1D2A36;
  --line-strong:  #2B3D4D;

  /* Ink */
  --ink:          #E9EFF3;
  --ink-2:        #A8B8C4;
  --ink-3:        #8397A5;

  /* Accent — used only for boundaries, active state and the control plane */
  --accent:       #2FD3C4;
  --accent-deep:  #16706B;
  --accent-ghost: rgba(47, 211, 196, 0.09);
  --accent-line:  rgba(47, 211, 196, 0.30);

  /* Semantic — statutory notices only, never decorative */
  --notice:       #E0B45C;
  --notice-ghost: rgba(224, 180, 92, 0.08);

  /* Type */
  --font-display: "Iowan Old Style", "Charter", "Bitstream Charter",
                  "Source Serif 4", Cambria, Georgia, serif;
  --font-body:    system-ui, -apple-system, "Segoe UI", Roboto,
                  "Helvetica Neue", Arial, sans-serif;
  --font-mono:    ui-monospace, "SF Mono", SFMono-Regular, Menlo, Consolas,
                  "Liberation Mono", monospace;

  /* Scale */
  --t-xs:    0.6875rem;
  --t-sm:    0.8125rem;
  --t-base:  1rem;
  --t-md:    1.0625rem;
  --t-lg:    1.375rem;
  --t-xl:    1.75rem;
  --t-2xl:   2.125rem;

  /* Rhythm */
  --gap-1:  0.375rem;
  --gap-2:  0.75rem;
  --gap-3:  1.25rem;
  --gap-4:  2rem;
  --gap-5:  3rem;
  --gap-6:  4.5rem;
  --gap-7:  7rem;

  --measure: 68ch;
  --shell:   1180px;
  --rail:    9.5rem;

  --ease: cubic-bezier(0.22, 0.61, 0.36, 1);
}

/* --- 2. Reset and base --------------------------------------------------- */

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

html {
  -webkit-text-size-adjust: 100%;
  scroll-behavior: smooth;
  scroll-padding-top: 6rem;
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  *, *::before, *::after {
    animation-duration: 0.001ms !important;
    animation-iteration-count: 1 !important;
    transition-duration: 0.001ms !important;
  }
}

body {
  margin: 0;
  background: var(--ground);
  color: var(--ink);
  font-family: var(--font-body);
  font-size: var(--t-md);
  line-height: 1.65;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

/* Faint engineering grid — a ground, not a decoration party. */
body::before {
  content: "";
  position: fixed;
  inset: 0;
  z-index: -1;
  pointer-events: none;
  background-image:
    linear-gradient(to right, rgba(255, 255, 255, 0.016) 1px, transparent 1px),
    linear-gradient(to bottom, rgba(255, 255, 255, 0.016) 1px, transparent 1px);
  background-size: 96px 96px;
  mask-image: radial-gradient(ellipse 120% 80% at 50% 0%, #000 20%, transparent 78%);
}

h1, h2, h3, h4 {
  font-family: var(--font-display);
  font-weight: 600;
  line-height: 1.14;
  letter-spacing: -0.012em;
  text-wrap: balance;
  margin: 0;
}

p { margin: 0; }
ul, ol { margin: 0; padding: 0; }

a {
  color: var(--ink);
  text-decoration-color: var(--accent-line);
  text-decoration-thickness: 1px;
  text-underline-offset: 0.22em;
  transition: color 0.18s var(--ease), text-decoration-color 0.18s var(--ease);
}
a:hover { color: var(--accent); text-decoration-color: var(--accent); }

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

::selection { background: var(--accent-deep); color: #F2FFFD; }

/* --- 3. Utilities -------------------------------------------------------- */

.shell {
  width: 100%;
  max-width: var(--shell);
  margin-inline: auto;
  padding-inline: clamp(1.25rem, 5vw, 3rem);
}

.measure { max-width: var(--measure); }

.mono {
  font-family: var(--font-mono);
  font-size: var(--t-xs);
  letter-spacing: 0.1em;
  text-transform: uppercase;
  color: var(--ink-3);
}

.skip {
  position: absolute;
  left: -9999px;
  top: 0;
  z-index: 100;
  background: var(--accent);
  color: #04140F;
  padding: 0.75rem 1.25rem;
  font-family: var(--font-mono);
  font-size: var(--t-sm);
}
.skip:focus { left: 0; }

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

/* --- 4. Masthead --------------------------------------------------------- */

.masthead {
  position: sticky;
  top: 0;
  z-index: 40;
  background: rgba(10, 15, 21, 0.86);
  backdrop-filter: blur(14px) saturate(140%);
  border-bottom: 1px solid var(--line);
}

.masthead__inner {
  display: flex;
  align-items: center;
  gap: var(--gap-4);
  min-height: 4.25rem;
}

.brand {
  display: flex;
  align-items: center;
  gap: 0.7rem;
  text-decoration: none;
  flex: 0 0 auto;
}
.brand:hover { color: var(--ink); }
.brand__mark { display: block; width: 26px; height: 26px; flex: 0 0 auto; }
.brand__name {
  font-family: var(--font-mono);
  font-size: 0.9375rem;
  letter-spacing: 0.02em;
  color: var(--ink);
}
.brand__sub {
  display: block;
  font-family: var(--font-mono);
  font-size: 0.625rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--ink-3);
  margin-top: 0.1rem;
}

.topnav {
  margin-left: auto;
  display: flex;
  align-items: center;
  gap: 0.25rem;
  overflow-x: auto;
  scrollbar-width: none;
  -webkit-overflow-scrolling: touch;
}
.topnav::-webkit-scrollbar { display: none; }

.topnav a {
  font-family: var(--font-mono);
  font-size: var(--t-xs);
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--ink-3);
  text-decoration: none;
  padding: 0.5rem 0.6rem;
  white-space: nowrap;
  border-bottom: 1px solid transparent;
}
.topnav a:hover { color: var(--ink); }
.topnav a[aria-current="true"] {
  color: var(--accent);
  border-bottom-color: var(--accent);
}

.topnav__cta {
  margin-left: 0.5rem;
  border: 1px solid var(--line-strong) !important;
  color: var(--ink) !important;
  padding: 0.45rem 0.85rem !important;
}
.topnav__cta:hover {
  border-color: var(--accent) !important;
  color: var(--accent) !important;
}

@media (max-width: 900px) {
  .masthead__inner { flex-wrap: wrap; min-height: 0; padding-block: 0.75rem; gap: 0.75rem; }
  .topnav { margin-left: 0; width: 100%; order: 3; padding-bottom: 0.25rem; }
  .brand__sub { display: none; }
}

/* --- 5. Hero ------------------------------------------------------------- */

.hero { padding-block: clamp(3.5rem, 9vw, 7rem) var(--gap-5); }

.hero__eyebrow {
  display: flex;
  align-items: center;
  gap: 0.75rem;
  margin-bottom: var(--gap-3);
}
.hero__eyebrow span { font-family: var(--font-mono); font-size: var(--t-xs);
  letter-spacing: 0.16em; text-transform: uppercase; color: var(--ink-3); }
.hero__eyebrow .dot {
  width: 7px; height: 7px; border-radius: 50%;
  background: var(--accent);
  box-shadow: 0 0 0 4px var(--accent-ghost);
  animation: pulse 3.4s var(--ease) infinite;
}
@keyframes pulse {
  0%, 100% { box-shadow: 0 0 0 3px var(--accent-ghost); }
  50%      { box-shadow: 0 0 0 8px rgba(47, 211, 196, 0.02); }
}

.hero h1 {
  font-size: clamp(2.35rem, 6.2vw, 4.25rem);
  max-width: 19ch;
  margin-bottom: var(--gap-3);
}
.hero h1 em {
  font-style: normal;
  color: var(--accent);
  /* underline drawn as a boundary tick, echoing the environment frames */
  box-shadow: inset 0 -2px 0 var(--accent-line);
}

.hero__lede {
  font-size: clamp(1.0625rem, 1.6vw, 1.25rem);
  color: var(--ink-2);
  max-width: 58ch;
  margin-bottom: var(--gap-4);
}

.actions { display: flex; flex-wrap: wrap; gap: 0.75rem; }

.btn {
  display: inline-flex;
  align-items: center;
  gap: 0.6rem;
  font-family: var(--font-mono);
  font-size: var(--t-sm);
  letter-spacing: 0.06em;
  text-decoration: none;
  padding: 0.8rem 1.35rem;
  border: 1px solid var(--line-strong);
  color: var(--ink);
  background: transparent;
  transition: border-color 0.18s var(--ease), background 0.18s var(--ease),
              color 0.18s var(--ease);
}
.btn:hover { border-color: var(--accent); color: var(--accent); background: var(--accent-ghost); }
.btn--primary {
  background: var(--accent);
  border-color: var(--accent);
  color: #04130F;
  font-weight: 600;
}
.btn--primary:hover { background: #4EE3D5; border-color: #4EE3D5; color: #04130F; }

/* Status strip — neutral operating facts, no claims of scale or performance. */
.status {
  margin-top: var(--gap-5);
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(11rem, 1fr));
  border: 1px solid var(--line);
  background: linear-gradient(180deg, var(--surface), var(--ground-2));
}
.status div {
  padding: 1rem 1.15rem;
  border-right: 1px solid var(--line);
}
.status div:last-child { border-right: 0; }
.status dt {
  font-family: var(--font-mono);
  font-size: 0.625rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--ink-3);
  margin-bottom: 0.3rem;
}
.status dd {
  margin: 0;
  font-family: var(--font-mono);
  font-size: var(--t-sm);
  color: var(--ink);
  font-variant-numeric: tabular-nums;
}
.status dd a {
  color: var(--ink);
  text-decoration: underline;
  text-decoration-color: var(--accent-line);
  text-underline-offset: 0.28em;
}
.status dd a:hover,
.status dd a:focus-visible { color: var(--accent); text-decoration-color: var(--accent); }
@media (max-width: 640px) {
  .status div { border-right: 0; border-bottom: 1px solid var(--line); }
  .status div:last-child { border-bottom: 0; }
}

/* --- 6. Clause layout (the document rail) -------------------------------- */

.clause {
  border-top: 1px solid var(--line);
  padding-block: var(--gap-6);
  scroll-margin-top: 5.5rem;
}

.clause__grid {
  display: grid;
  gap: var(--gap-4);
}

@media (min-width: 1000px) {
  .clause__grid {
    grid-template-columns: var(--rail) minmax(0, 1fr);
    gap: var(--gap-5);
  }
}

.clause__rail { position: relative; }
@media (min-width: 1000px) {
  .clause__rail {
    position: sticky;
    top: 6.5rem;
    align-self: start;
    border-left: 2px solid var(--line);
    padding-left: 1rem;
    transition: border-color 0.4s var(--ease);
  }
  .clause.is-active .clause__rail { border-left-color: var(--accent); }
}

.clause__id {
  font-family: var(--font-mono);
  font-size: var(--t-xs);
  letter-spacing: 0.14em;
  color: var(--accent);
  display: block;
}
.clause__tag {
  font-family: var(--font-mono);
  font-size: 0.625rem;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ink-3);
  display: block;
  margin-top: 0.35rem;
}

.clause h2 {
  font-size: clamp(1.75rem, 3.4vw, var(--t-2xl));
  margin-bottom: var(--gap-3);
  max-width: 22ch;
}

.prose { display: flex; flex-direction: column; gap: var(--gap-3); max-width: var(--measure); }
.prose p { color: var(--ink-2); }
.prose p.lead { color: var(--ink); font-size: 1.125rem; }
.prose strong { color: var(--ink); font-weight: 600; }

/* --- 7. Figures and diagrams --------------------------------------------- */

figure { margin: 0; }

.figure {
  margin-top: var(--gap-5);
  border: 1px solid var(--line);
  background:
    radial-gradient(120% 90% at 50% 0%, rgba(47, 211, 196, 0.045), transparent 62%),
    var(--ground-2);
}
.figure__frame { overflow-x: auto; padding: clamp(1rem, 3vw, 2rem); }
.figure svg { display: block; width: 100%; min-width: 640px; height: auto; }
.figure figcaption {
  border-top: 1px solid var(--line);
  padding: 0.9rem clamp(1rem, 3vw, 2rem);
  font-family: var(--font-mono);
  font-size: var(--t-xs);
  line-height: 1.7;
  letter-spacing: 0.03em;
  color: var(--ink-3);
}

/* Diagram element classes — SVG is inline, styled from here. */
.d-box   { fill: var(--surface); stroke: var(--line-strong); stroke-width: 1; }
.d-box--plane { fill: rgba(47, 211, 196, 0.07); stroke: var(--accent); }
.d-box--muted { fill: var(--ground-2); stroke: var(--line); }
.d-hdr   { fill: rgba(255, 255, 255, 0.028); stroke: none; }
.d-line  { stroke: var(--line-strong); stroke-width: 1.25; fill: none; }
.d-line--live { stroke: var(--accent-line); }
.d-cut   { stroke: var(--line-strong); stroke-width: 1.25; stroke-dasharray: 5 5; fill: none; }
.d-x     { stroke: var(--notice); stroke-width: 1.6; }
.d-t     { font-family: var(--font-mono); font-size: 12px; fill: var(--ink-2); }
.d-t--sm { font-size: 10.5px; fill: var(--ink-3); letter-spacing: 0.06em; }
.d-t--hd { font-size: 11px; fill: var(--ink); letter-spacing: 0.12em; }
.d-t--ac { fill: var(--accent); }
.d-t--nt { fill: var(--notice); }
.d-dot   { fill: var(--accent); }

/* Telemetry pulse travelling along the control-plane bus. */
.d-pulse {
  fill: var(--accent);
  animation: flow 6s linear infinite;
}
.d-pulse--b { animation-delay: 2s; }
.d-pulse--c { animation-delay: 4s; }
@keyframes flow {
  0%   { opacity: 0; transform: translateY(0); }
  10%  { opacity: 1; }
  85%  { opacity: 1; }
  100% { opacity: 0; transform: translateY(56px); }
}
@media (prefers-reduced-motion: reduce) { .d-pulse { display: none; } }

/* Isolation demonstration: focusing one environment dims the others. */
.d-env { transition: opacity 0.3s var(--ease); }
.diagram--iso:hover .d-env { opacity: 0.28; }
.diagram--iso .d-env:hover { opacity: 1; }

/* --- 8. Stage sequence (a real ordered process) -------------------------- */

.stages {
  margin-top: var(--gap-4);
  display: grid;
  gap: 0;
  counter-reset: stage;
}
.stage {
  display: grid;
  grid-template-columns: 3.5rem minmax(0, 1fr);
  gap: var(--gap-3);
  padding-block: var(--gap-3);
  border-top: 1px solid var(--line);
  position: relative;
}
.stage:first-child { border-top: 0; }
.stage__n {
  font-family: var(--font-mono);
  font-size: var(--t-xs);
  letter-spacing: 0.08em;
  color: var(--ink-3);
  padding-top: 0.3rem;
  position: relative;
}
.stage__n::after {
  /* the rail that makes the sequence read as a sequence */
  content: "";
  position: absolute;
  left: 1.55rem;
  top: 2.1rem;
  bottom: -1.6rem;
  width: 1px;
  background: linear-gradient(var(--line-strong), transparent);
}
.stage:last-child .stage__n::after { display: none; }
.stage h3 {
  font-size: 1.1875rem;
  font-family: var(--font-body);
  font-weight: 600;
  letter-spacing: -0.005em;
  margin-bottom: 0.4rem;
}
.stage p { color: var(--ink-2); font-size: var(--t-base); max-width: 62ch; }
.stage:hover .stage__n { color: var(--accent); }

/* --- 9. Component / principle grids -------------------------------------- */

.grid-2 {
  margin-top: var(--gap-4);
  display: grid;
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
  grid-template-columns: repeat(auto-fit, minmax(17rem, 1fr));
}
.cell {
  background: var(--ground-2);
  padding: 1.4rem 1.5rem;
  transition: background 0.2s var(--ease);
}
.cell:hover { background: var(--surface); }
.cell__k {
  font-family: var(--font-mono);
  font-size: 0.625rem;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--accent);
  display: block;
  margin-bottom: 0.55rem;
}
.cell h3 {
  font-family: var(--font-body);
  font-size: var(--t-base);
  font-weight: 600;
  margin-bottom: 0.35rem;
}
.cell p { color: var(--ink-2); font-size: 0.9375rem; line-height: 1.6; }

/* Bill-of-materials list for environment components */
.bom {
  margin-top: var(--gap-4);
  list-style: none;
  border-top: 1px solid var(--line);
}
.bom li {
  display: grid;
  grid-template-columns: 5.5rem minmax(0, 1fr);
  gap: var(--gap-2);
  align-items: baseline;
  padding: 0.7rem 0;
  border-bottom: 1px solid var(--line);
  font-size: var(--t-base);
}
.bom li span {
  font-family: var(--font-mono);
  font-size: var(--t-xs);
  letter-spacing: 0.1em;
  color: var(--ink-3);
  font-variant-numeric: tabular-nums;
}
.bom li:hover span { color: var(--accent); }

/* --- 10. Withheld register (research confidentiality) -------------------- */

.withheld { margin-top: var(--gap-4); list-style: none; display: grid; gap: 1px;
  background: var(--line); border: 1px solid var(--line); }
.withheld li {
  background: var(--ground-2);
  display: flex;
  align-items: center;
  gap: 1rem;
  padding: 0.85rem 1.1rem;
  font-size: 0.9375rem;
  color: var(--ink-2);
}
.withheld li::before {
  content: "WITHHELD";
  flex: 0 0 auto;
  font-family: var(--font-mono);
  font-size: 0.5625rem;
  letter-spacing: 0.14em;
  color: var(--ink-3);
  border: 1px solid var(--line-strong);
  padding: 0.2rem 0.45rem;
}
.withheld li::after {
  content: "";
  flex: 1 1 auto;
  height: 10px;
  min-width: 1.5rem;
  background-image: repeating-linear-gradient(
    -45deg, var(--line) 0 1px, transparent 1px 6px);
}
@media (max-width: 640px) { .withheld li::after { display: none; } }

/* --- 11. Callouts -------------------------------------------------------- */

.callout {
  margin-top: var(--gap-4);
  border: 1px solid var(--line-strong);
  border-left: 2px solid var(--accent);
  background: var(--surface);
  padding: 1.15rem 1.35rem;
  max-width: var(--measure);
}
.callout p { color: var(--ink-2); font-size: 0.9375rem; }
.callout .mono { display: block; margin-bottom: 0.5rem; color: var(--accent); }

.callout--notice {
  border-left-color: var(--notice);
  background: var(--notice-ghost);
}
.callout--notice .mono { color: var(--notice); }
.callout--notice p { color: var(--ink); }

/* --- 12. FAQ ------------------------------------------------------------- */

.faq { margin-top: var(--gap-4); border-top: 1px solid var(--line); }
.faq details { border-bottom: 1px solid var(--line); }
.faq summary {
  cursor: pointer;
  list-style: none;
  padding: 1.15rem 2.5rem 1.15rem 0;
  position: relative;
  font-size: var(--t-base);
  font-weight: 600;
  color: var(--ink);
  transition: color 0.18s var(--ease);
}
.faq summary::-webkit-details-marker { display: none; }
.faq summary:hover { color: var(--accent); }
.faq summary::after {
  content: "+";
  position: absolute;
  right: 0.25rem;
  top: 50%;
  transform: translateY(-50%);
  font-family: var(--font-mono);
  font-size: 1.1rem;
  color: var(--ink-3);
  transition: transform 0.22s var(--ease), color 0.18s var(--ease);
}
.faq details[open] summary::after { content: "\2212"; color: var(--accent); }
.faq details p {
  padding: 0 2.5rem 1.3rem 0;
  color: var(--ink-2);
  max-width: 64ch;
  font-size: 0.9375rem;
}

/* --- 13. Contact --------------------------------------------------------- */

.contact-grid {
  margin-top: var(--gap-4);
  display: grid;
  gap: 1px;
  background: var(--line);
  border: 1px solid var(--line);
  grid-template-columns: repeat(auto-fit, minmax(15rem, 1fr));
}
.contact-grid > div { background: var(--ground-2); padding: 1.4rem 1.5rem; }
.contact-grid dt {
  font-family: var(--font-mono); font-size: 0.625rem; letter-spacing: 0.16em;
  text-transform: uppercase; color: var(--ink-3); margin-bottom: 0.45rem;
}
.contact-grid dd { margin: 0; font-size: 0.9375rem; color: var(--ink); }
.contact-grid dd a { font-family: var(--font-mono); font-size: 0.875rem; }

/* --- 14. Footer ---------------------------------------------------------- */

.foot {
  border-top: 1px solid var(--line);
  background: var(--ground-2);
  padding-block: var(--gap-5) var(--gap-4);
  margin-top: var(--gap-6);
}
.foot__top {
  display: grid;
  gap: var(--gap-4);
  grid-template-columns: repeat(auto-fit, minmax(14rem, 1fr));
  padding-bottom: var(--gap-4);
  border-bottom: 1px solid var(--line);
}
.foot h2 {
  font-family: var(--font-mono);
  font-size: 0.625rem;
  font-weight: 400;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--ink-3);
  margin-bottom: 0.8rem;
}
.foot ul { list-style: none; display: flex; flex-direction: column; gap: 0.45rem; }
.foot a { font-size: 0.9375rem; text-decoration: none; color: var(--ink-2); }
.foot a:hover { color: var(--accent); }
.foot address {
  font-style: normal;
  font-size: 0.9375rem;
  color: var(--ink-2);
  line-height: 1.8;
}
.foot__note {
  font-size: 0.9375rem;
  color: var(--ink-2);
  max-width: 34ch;
}

/* Publication notice: required to be legible, never reduced to fine print. */
.pubnotice {
  margin-top: var(--gap-4);
  border: 1px solid rgba(224, 180, 92, 0.35);
  background: var(--notice-ghost);
  padding: 1.1rem 1.3rem;
  font-size: 0.9375rem;
  color: var(--ink);
  line-height: 1.7;
}
.pubnotice b {
  display: block;
  font-family: var(--font-mono);
  font-size: var(--t-xs);
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--notice);
  font-weight: 400;
  margin-bottom: 0.45rem;
}

.foot__bottom {
  margin-top: var(--gap-4);
  display: flex;
  flex-wrap: wrap;
  gap: var(--gap-3);
  justify-content: space-between;
  align-items: baseline;
}
.foot__bottom p {
  font-family: var(--font-mono);
  font-size: var(--t-xs);
  letter-spacing: 0.06em;
  color: var(--ink-3);
  font-variant-numeric: tabular-nums;
}

/* --- 15. Legal document pages -------------------------------------------- */

.doc { padding-block: var(--gap-6) var(--gap-5); }
.doc__head { border-bottom: 1px solid var(--line); padding-bottom: var(--gap-4); margin-bottom: var(--gap-5); }
.doc__head h1 { font-size: clamp(2rem, 5vw, 3rem); margin-bottom: var(--gap-2); }
.doc__head p { color: var(--ink-2); max-width: var(--measure); }

.doc__body { display: grid; gap: var(--gap-5); max-width: 78ch; }
.doc section { display: flex; flex-direction: column; gap: var(--gap-2); }
.doc section > h2 {
  font-size: var(--t-lg);
  margin-bottom: 0.35rem;
}
.doc section > h3 {
  font-family: var(--font-body);
  font-size: 1.0625rem;
  font-weight: 600;
  letter-spacing: -0.004em;
  color: var(--ink);
  margin-top: 0.6rem;
}

.doc section > h2 .num {
  font-family: var(--font-mono);
  font-size: var(--t-xs);
  letter-spacing: 0.12em;
  color: var(--accent);
  margin-right: 0.7rem;
  vertical-align: 0.22em;
}
.doc p, .doc li { color: var(--ink-2); font-size: var(--t-base); }
.doc ul { list-style: none; display: flex; flex-direction: column; gap: 0.5rem; }
.doc ul li { position: relative; padding-left: 1.4rem; }
.doc ul li::before {
  content: "";
  position: absolute;
  left: 0.15rem;
  top: 0.62em;
  width: 6px; height: 6px;
  border: 1px solid var(--accent);
}
.doc dl { display: grid; gap: 0.6rem; margin: 0; }
@media (min-width: 720px) { .doc dl { grid-template-columns: 15rem minmax(0, 1fr); gap: 0.6rem 1.5rem; } }
.doc dt {
  font-family: var(--font-mono); font-size: var(--t-sm); letter-spacing: 0.04em;
  color: var(--ink);
}
.doc dd { margin: 0; color: var(--ink-2); font-size: var(--t-base); }

.doc__toc {
  border: 1px solid var(--line);
  background: var(--ground-2);
  padding: 1.25rem 1.4rem;
  margin-bottom: var(--gap-5);
  max-width: 78ch;
}
.doc__toc ol { list-style: none; counter-reset: toc; display: grid; gap: 0.4rem;
  grid-template-columns: repeat(auto-fit, minmax(15rem, 1fr)); }
.doc__toc li { counter-increment: toc; }
.doc__toc a {
  font-family: var(--font-mono); font-size: var(--t-sm); color: var(--ink-2);
  text-decoration: none;
}
.doc__toc a::before {
  content: counter(toc, decimal-leading-zero) " ";
  color: var(--accent);
}
.doc__toc a:hover { color: var(--accent); }
.doc__toc > .mono { display: block; margin-bottom: 0.8rem; }

/* --- 15b. Small utilities (kept as classes so no inline styles are needed,
       which is what allows a strict Content-Security-Policy) --------------- */

.mt-4 { margin-top: var(--gap-4); }
.mt-2 { margin-top: 0.5rem; }
.callout--wide { max-width: none; }
.nb { white-space: nowrap; }

/* --- 16. Scroll reveal --------------------------------------------------- */

.reveal { opacity: 0; transform: translateY(14px); }
.reveal.is-in {
  opacity: 1;
  transform: none;
  transition: opacity 0.6s var(--ease), transform 0.6s var(--ease);
}
@media (prefers-reduced-motion: reduce) {
  .reveal { opacity: 1; transform: none; }
}
/* If JS never runs, content must still be visible. */
.no-js .reveal { opacity: 1; transform: none; }