/* ==========================================================================
   axiom — Bayesian causal decision science
   --------------------------------------------------------------------------
   The design follows the library's own fourth rule: every number carries its
   provenance. Key figures are set as interval readouts that state their
   definition and mass; every chart carries a stamp naming the call that made
   it. Red is reserved — it marks a crossed boundary and never a data series.
   ========================================================================== */

/* -- tokens ---------------------------------------------------------------- */

:root {
  color-scheme: light;

  --paper:    #f4f7fa;
  --panel:    #ffffff;
  --panel-2:  #eaeff5;
  --ink:      #0f1720;
  --ink-2:    #48545f;
  --ink-3:    #74808d;
  --rule:     #d8e0e9;
  --rule-2:   #e8edf3;
  --grid:     #e2e8ef;

  --accent:      #2a78d6;
  --accent-deep: #1c5cab;
  --accent-wash: #e6effb;

  /* reserved: a threshold that was crossed. never a series colour. */
  --boundary:      #d03b3b;
  --boundary-wash: #f7e4e3;
  --good:          #0ca30c;
  --warn:          #fab219;

  /* validated categorical slots (light) */
  --s1: #2a78d6;  --s2: #eb6834;  --s3: #1baf7a;  --s4: #eda100;
  --s5: #e87ba4;  --s6: #008300;  --s7: #4a3aa7;  --s8: #e34948;

  --f-display: "IBM Plex Sans Condensed", "Helvetica Neue", Arial, sans-serif;
  --f-body: "IBM Plex Serif", Georgia, "Times New Roman", serif;
  --f-ui: "IBM Plex Sans", system-ui, -apple-system, Segoe UI, sans-serif;
  --f-mono: "IBM Plex Mono", ui-monospace, SFMono-Regular, Menlo, monospace;

  --wrap: 1200px;
  --measure: 68ch;
  --pad: clamp(20px, 5vw, 52px);
  --shadow: 0 1px 2px rgba(16, 32, 52, .05), 0 8px 24px -12px rgba(16, 32, 52, .16);
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    color-scheme: dark;
    --paper:   #0d1219;
    --panel:   #141c25;
    --panel-2: #1a232e;
    --ink:     #edf1f6;
    --ink-2:   #a3aebc;
    --ink-3:   #7b8794;
    --rule:    #253040;
    --rule-2:  #1d2735;
    --grid:    #202b39;

    --accent:      #3987e5;
    --accent-deep: #6da7ec;
    --accent-wash: #16283f;

    --boundary:      #e05f5c;
    --boundary-wash: #35201f;

    --s1: #3987e5;  --s2: #d95926;  --s3: #199e70;  --s4: #c98500;
    --s5: #d55181;  --s6: #008300;  --s7: #9085e9;  --s8: #e66767;
    --shadow: 0 1px 2px rgba(0, 0, 0, .4), 0 10px 30px -14px rgba(0, 0, 0, .7);
  }
}

:root[data-theme="dark"] {
  color-scheme: dark;
  --paper:   #0d1219;
  --panel:   #141c25;
  --panel-2: #1a232e;
  --ink:     #edf1f6;
  --ink-2:   #a3aebc;
  --ink-3:   #7b8794;
  --rule:    #253040;
  --rule-2:  #1d2735;
  --grid:    #202b39;

  --accent:      #3987e5;
  --accent-deep: #6da7ec;
  --accent-wash: #16283f;

  --boundary:      #e05f5c;
  --boundary-wash: #35201f;

  --s1: #3987e5;  --s2: #d95926;  --s3: #199e70;  --s4: #c98500;
  --s5: #d55181;  --s6: #008300;  --s7: #9085e9;  --s8: #e66767;
  --shadow: 0 1px 2px rgba(0, 0, 0, .4), 0 10px 30px -14px rgba(0, 0, 0, .7);
}

/* -- base ------------------------------------------------------------------ */

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

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

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--f-body);
  font-size: 17px;
  line-height: 1.66;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

h1, h2, h3, h4 { font-family: var(--f-display); font-weight: 700; line-height: 1.05; margin: 0; }
h1 { font-size: clamp(2.6rem, 6.4vw, 4.6rem); letter-spacing: -.022em; }
h2 { font-size: clamp(1.9rem, 3.6vw, 2.7rem); letter-spacing: -.016em; }
h3 { font-size: clamp(1.25rem, 2vw, 1.5rem); letter-spacing: -.01em; }
h4 { font-size: 1.05rem; letter-spacing: -.005em; font-family: var(--f-ui); font-weight: 600; }

p { margin: 0 0 1.1em; }
a { color: var(--accent-deep); text-decoration-thickness: 1px; text-underline-offset: 2px; }
a:hover { color: var(--accent); }
strong { font-weight: 600; }
code { font-family: var(--f-mono); font-size: .87em; }
:focus-visible { outline: 2px solid var(--accent); outline-offset: 3px; border-radius: 2px; }

.skip {
  position: absolute; left: -9999px; top: 8px; z-index: 100;
  background: var(--accent); color: #fff; padding: 10px 16px; border-radius: 6px;
  font-family: var(--f-ui); font-size: .9rem;
}
.skip:focus { left: 12px; }

.wrap { max-width: var(--wrap); margin-inline: auto; padding-inline: var(--pad); }
.prose { max-width: var(--measure); }
.lede { font-size: 1.18rem; line-height: 1.6; color: var(--ink-2); }

/* -- top bar: the nav is the workflow -------------------------------------- */

.topbar {
  position: sticky; top: 0; z-index: 50;
  background: color-mix(in srgb, var(--paper) 88%, transparent);
  backdrop-filter: saturate(1.6) blur(12px);
  border-bottom: 1px solid var(--rule);
}
.topbar-in {
  max-width: var(--wrap); margin-inline: auto; padding: 0 var(--pad);
  display: flex; align-items: center; gap: clamp(12px, 2.5vw, 30px); min-height: 60px;
}

.brand {
  display: inline-flex; align-items: center; gap: 9px; flex: none;
  font-family: var(--f-display); font-weight: 700; font-size: 1.32rem;
  letter-spacing: -.02em; color: var(--ink); text-decoration: none;
}
.brand-mark {
  width: 15px; height: 15px; flex: none; border-radius: 50%;
  border: 2.5px solid var(--accent);
  /* a point with an interval around it — the library's atom */
  box-shadow: 0 0 0 3px color-mix(in srgb, var(--accent) 16%, transparent);
}

/* the chain of pillars, in working order */
.chain { display: flex; align-items: center; flex: 1 1 auto; min-width: 0; overflow-x: auto;
  scrollbar-width: none; }
.chain::-webkit-scrollbar { display: none; }
.step {
  display: inline-flex; align-items: baseline; gap: 6px; flex: none;
  padding: 6px 9px; border-radius: 6px; text-decoration: none;
  font-family: var(--f-ui); font-size: .87rem; font-weight: 500; color: var(--ink-2);
  white-space: nowrap;
}
.step:hover { background: var(--panel-2); color: var(--ink); }
.step-n {
  font-family: var(--f-mono); font-size: .68rem; font-weight: 600;
  color: var(--ink-3); font-variant-numeric: tabular-nums;
}
.step-on { color: var(--ink); background: var(--accent-wash); }
.step-on .step-n { color: var(--accent); }
.step-link { flex: none; width: 12px; height: 1px; background: var(--rule); }

.navx-wrap { display: flex; gap: 4px; flex: none; }
.navx {
  font-family: var(--f-ui); font-size: .87rem; font-weight: 500; color: var(--ink-2);
  text-decoration: none; padding: 6px 9px; border-radius: 6px; white-space: nowrap;
}
.navx:hover { background: var(--panel-2); color: var(--ink); }
.navx-on { color: var(--ink); background: var(--panel-2); }

.theme {
  flex: none; width: 34px; height: 34px; border-radius: 8px; cursor: pointer;
  border: 1px solid var(--rule); background: var(--panel); display: grid; place-items: center;
}
.theme:hover { border-color: var(--accent); }
.theme-ico {
  width: 14px; height: 14px; border-radius: 50%;
  background: linear-gradient(90deg, var(--ink) 0 50%, transparent 50% 100%);
  border: 1.6px solid var(--ink); box-sizing: border-box;
}

/* The chain drops to its own row once the brand, five pillars, the secondary links
   and the theme button stop fitting on one. That happens sooner than it used to:
   naming the two case studies separately ("HYPER-3", "GEIGER-1911") in place of a
   single "Case study" adds a fifth secondary link and roughly a hundred pixels, so
   the breakpoint moves out with it. Everything here is `flex: none` above 560px and
   cannot give, so a breakpoint that is too low overflows the viewport rather than
   crowding. */
@media (max-width: 1024px) {
  .chain { order: 3; flex-basis: 100%; padding-bottom: 8px; }
  .topbar-in { flex-wrap: wrap; padding-top: 8px; }
  .step-link { width: 8px; }
}

/* On a narrow phone the brand, the secondary links and the theme button together
   are wider than the viewport, and `flex: none` means they cannot give. Let the
   link group shrink and scroll rather than pushing the whole page sideways. */
@media (max-width: 560px) {
  .topbar-in { gap: 10px; }
  .navx-wrap {
    flex: 1 1 auto; min-width: 0; overflow-x: auto; scrollbar-width: none;
    justify-content: flex-end;
  }
  .navx-wrap::-webkit-scrollbar { display: none; }
  .navx { padding: 6px 7px; }
  .brand { font-size: 1.18rem; }
}

/* -- structural bits ------------------------------------------------------- */

.eyebrow {
  font-family: var(--f-mono); font-size: .72rem; font-weight: 500;
  letter-spacing: .13em; text-transform: uppercase; color: var(--ink-3);
  margin: 0 0 14px; display: flex; align-items: center; gap: 10px;
}
.eyebrow::before {
  content: ""; width: 18px; height: 2px; background: var(--accent); flex: none;
}

section { padding-block: clamp(48px, 7vw, 92px); }
section + section { border-top: 1px solid var(--rule-2); }
.section-head { max-width: var(--measure); margin-bottom: 38px; }
.section-head p { color: var(--ink-2); margin-bottom: 0; }
.section-head h2 + p { margin-top: 14px; }

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

.hero { padding-block: clamp(40px, 6vw, 76px) clamp(40px, 6vw, 80px); }
.hero-grid {
  display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1.08fr);
  gap: clamp(32px, 5vw, 64px); align-items: center;
}
@media (max-width: 940px) { .hero-grid { grid-template-columns: 1fr; } }

.hero h1 { margin-bottom: 22px; }
.hero h1 em {
  font-style: normal; color: var(--boundary);
  /* the one red thing above the fold: a boundary that was crossed */
}
.hero-sub { font-size: 1.16rem; color: var(--ink-2); max-width: 54ch; }
.hero-sub strong { color: var(--ink); }

.hero-cta { display: flex; flex-wrap: wrap; gap: 12px; margin-top: 28px; align-items: center; }
.btn {
  font-family: var(--f-ui); font-size: .93rem; font-weight: 500;
  padding: 11px 20px; border-radius: 8px; text-decoration: none;
  border: 1px solid transparent; display: inline-flex; align-items: center; gap: 8px;
}
.btn-1 { background: var(--accent); color: #fff; }
.btn-1:hover { background: var(--accent-deep); color: #fff; }
.btn-2 { background: var(--panel); color: var(--ink); border-color: var(--rule); }
.btn-2:hover { border-color: var(--accent); color: var(--ink); }

/* -- the interval readout: axiom's fourth rule, as a component -------------- */

.readout { font-family: var(--f-mono); display: block; }
.readout-v {
  font-size: clamp(1.5rem, 3vw, 2.1rem); font-weight: 600; letter-spacing: -.02em;
  color: var(--ink); font-variant-numeric: tabular-nums; line-height: 1.1;
}
.readout-v.is-boundary { color: var(--boundary); }
.readout-bar {
  position: relative; height: 11px; margin: 9px 0 5px; max-width: 220px;
}
.readout-bar::before {
  content: ""; position: absolute; left: 0; right: 0; top: 5px; height: 1.5px;
  background: var(--ink-3);
}
/* The point estimate, placed where it actually falls inside its interval —
   `--pos` is computed at build time, so a skewed posterior draws skewed. */
.readout-bar::after {
  content: ""; position: absolute; left: var(--pos, 50%); top: 0; width: 1.5px;
  height: 11px; background: var(--accent); transform: translateX(-50%);
}
.readout-bar i {
  position: absolute; top: 1px; width: 1.5px; height: 9px; background: var(--ink-3);
}
.readout-bar i:first-child { left: 0; }
.readout-bar i:last-child { right: 0; }
.readout-e {
  display: flex; justify-content: space-between; max-width: 220px;
  font-size: .78rem; color: var(--ink-3); font-variant-numeric: tabular-nums;
}
.readout-d {
  font-size: .72rem; color: var(--ink-3); margin-top: 7px; letter-spacing: .01em;
}
.readout-l {
  font-family: var(--f-ui); font-size: .82rem; color: var(--ink-2); margin-bottom: 5px;
}

/* -- figures & charts ------------------------------------------------------ */

.fig {
  margin: 0 0 8px; background: var(--panel); border: 1px solid var(--rule);
  border-radius: 12px; padding: 20px 20px 14px; box-shadow: var(--shadow);
}
.fig-head { margin-bottom: 14px; }
.fig-t {
  font-family: var(--f-ui); font-weight: 600; font-size: .98rem; color: var(--ink);
  margin: 0 0 4px;
}
.fig-s { font-size: .88rem; color: var(--ink-2); margin: 0; line-height: 1.5; font-family: var(--f-ui); }
.chart { width: 100%; position: relative; }
.chart svg { display: block; width: 100%; overflow: visible; }

/* the provenance stamp — every figure names the call that produced it */
.stamp {
  font-family: var(--f-mono); font-size: .705rem; color: var(--ink-3);
  margin: 12px 0 0; padding-top: 10px; border-top: 1px dashed var(--rule);
  line-height: 1.6; text-indent: -14px; padding-left: 14px;
}
.stamp::before { content: "↳ "; color: var(--accent); }
.stamp b { font-weight: 500; color: var(--ink-2); }

.legend {
  display: flex; flex-wrap: wrap; gap: 6px 18px; margin: 0 0 12px;
  font-family: var(--f-ui); font-size: .82rem; color: var(--ink-2);
}
.legend span { display: inline-flex; align-items: center; gap: 7px; }
.legend i {
  width: 14px; height: 3px; border-radius: 2px; background: var(--k, var(--s1)); flex: none;
}
.legend i.dash {
  height: 0; border-top: 2px dashed var(--k, var(--boundary)); border-radius: 0;
}
.legend i.dot { width: 9px; height: 9px; border-radius: 50%; }

/* tooltip */
.tip {
  position: absolute; pointer-events: none; z-index: 20; opacity: 0;
  transition: opacity .1s ease; background: var(--panel); color: var(--ink);
  border: 1px solid var(--rule); border-radius: 8px; padding: 9px 11px;
  font-family: var(--f-mono); font-size: .74rem; line-height: 1.55;
  box-shadow: var(--shadow); max-width: 260px;
  /* No `white-space: nowrap` here. It contradicts the max-width — a study label
     longer than 260px cannot wrap, so it runs out through the border instead of
     growing the box downward. The <br>s in every tooltip already decide where the
     lines break; wrapping is only ever the fallback for one long label. */
  overflow-wrap: anywhere;
}
.tip.on { opacity: 1; }
.tip b { color: var(--ink); font-weight: 600; }
.tip em { font-style: normal; color: var(--ink-3); }
@media (prefers-reduced-motion: reduce) { .tip { transition: none; } }

/* the table view every chart owes its reader */
.tbl-toggle {
  font-family: var(--f-ui); font-size: .78rem; color: var(--ink-2); background: none;
  border: 1px solid var(--rule); border-radius: 6px; padding: 4px 10px; cursor: pointer;
  margin-top: 12px;
}
.tbl-toggle:hover { border-color: var(--accent); color: var(--ink); }
.chart-tbl { display: none; margin-top: 12px; max-height: 340px; overflow: auto; }
.chart-tbl.on { display: block; }

/* -- tables ---------------------------------------------------------------- */

.tbl-wrap { overflow-x: auto; margin: 0 0 8px; }
table.t {
  border-collapse: collapse; width: 100%; font-family: var(--f-mono); font-size: .8rem;
  font-variant-numeric: tabular-nums;
}
table.t caption {
  text-align: left; font-family: var(--f-ui); font-size: .88rem; color: var(--ink-2);
  padding-bottom: 10px;
}
table.t th, table.t td { padding: 8px 14px 8px 0; text-align: right; white-space: nowrap; }
table.t th:first-child, table.t td:first-child { text-align: left; }
table.t th {
  font-weight: 500; font-size: .7rem; letter-spacing: .07em; text-transform: uppercase;
  color: var(--ink-3); border-bottom: 1px solid var(--rule); padding-bottom: 7px;
}
table.t td { border-bottom: 1px solid var(--rule-2); color: var(--ink-2); }
table.t td:first-child { color: var(--ink); }
table.t tr.hi td { background: var(--accent-wash); color: var(--ink); }
table.t tr.bad td { color: var(--boundary); }
table.t .num-good { color: var(--good); }
table.t .num-bad { color: var(--boundary); }

/* -- code ------------------------------------------------------------------ */

.code {
  position: relative; background: var(--panel); border: 1px solid var(--rule);
  border-radius: 12px; margin: 0 0 18px; box-shadow: var(--shadow); overflow: hidden;
}
.code-h {
  display: flex; align-items: center; justify-content: space-between; gap: 12px;
  padding: 9px 14px; border-bottom: 1px solid var(--rule-2); background: var(--panel-2);
}
.code-h span {
  font-family: var(--f-mono); font-size: .72rem; color: var(--ink-3); letter-spacing: .04em;
}
.copy {
  font-family: var(--f-ui); font-size: .74rem; color: var(--ink-2); background: none;
  border: 1px solid var(--rule); border-radius: 5px; padding: 3px 9px; cursor: pointer;
}
.copy:hover { border-color: var(--accent); color: var(--ink); }
.code pre {
  margin: 0; padding: 16px; overflow-x: auto; font-family: var(--f-mono);
  font-size: .805rem; line-height: 1.7; color: var(--ink);
}
.code pre .c { color: var(--ink-3); font-style: italic; }
.code pre .k { color: var(--s7); }
.code pre .s { color: var(--s3); }
.code pre .n { color: var(--s2); }
.code pre .f { color: var(--accent-deep); }
.code pre .o { color: var(--ink-2); }

/* a block of real terminal output, paired with the code that made it */
.out {
  background: var(--panel-2); border: 1px solid var(--rule); border-radius: 12px;
  padding: 0; margin: 0 0 18px; overflow: hidden;
}
.out-h {
  padding: 9px 14px; border-bottom: 1px solid var(--rule);
  font-family: var(--f-mono); font-size: .72rem; color: var(--ink-3); letter-spacing: .04em;
}
.out pre {
  margin: 0; padding: 16px; overflow-x: auto; font-family: var(--f-mono);
  font-size: .775rem; line-height: 1.72; color: var(--ink-2);
}
.out pre b { color: var(--ink); font-weight: 600; }
.out pre .hl { color: var(--accent-deep); font-weight: 600; }
.out pre .bad { color: var(--boundary); font-weight: 600; }
.out pre .ok { color: var(--good); font-weight: 600; }

.pair { display: grid; grid-template-columns: 1fr 1fr; gap: 18px; align-items: start; }
@media (max-width: 860px) { .pair { grid-template-columns: 1fr; } }

/* -- cards ----------------------------------------------------------------- */

.cards { display: grid; gap: 18px; grid-template-columns: repeat(auto-fit, minmax(min(320px, 100%), 1fr)); }
.card {
  background: var(--panel); border: 1px solid var(--rule); border-radius: 12px;
  padding: 22px; display: flex; flex-direction: column; text-decoration: none;
  color: inherit; box-shadow: var(--shadow);
}
a.card:hover { border-color: var(--accent); }
a.card:hover .card-go { color: var(--accent); gap: 10px; }
.card-n {
  font-family: var(--f-mono); font-size: .7rem; color: var(--accent); font-weight: 600;
  letter-spacing: .1em; margin-bottom: 12px;
}
.card h3 { margin-bottom: 9px; }
.card p { font-size: .93rem; color: var(--ink-2); margin-bottom: 16px; }
.card-f { margin-top: auto; }
.card-go {
  font-family: var(--f-ui); font-size: .85rem; color: var(--ink-2); font-weight: 500;
  display: inline-flex; align-items: center; gap: 6px; transition: gap .15s ease;
}
@media (prefers-reduced-motion: reduce) { .card-go { transition: none; } }

/* a number pulled out of a card, in the library's own idiom */
.card-stat {
  font-family: var(--f-mono); font-size: 1.05rem; font-weight: 600; color: var(--ink);
  font-variant-numeric: tabular-nums;
}
.card-stat small {
  display: block; font-family: var(--f-ui); font-size: .76rem; font-weight: 400;
  color: var(--ink-3); margin-top: 3px; letter-spacing: 0;
}

/* -- callouts -------------------------------------------------------------- */

.note {
  border-left: 2px solid var(--accent); background: var(--panel);
  padding: 16px 20px; border-radius: 0 10px 10px 0; margin: 0 0 20px;
}
.note p:last-child { margin-bottom: 0; }
.note-t {
  font-family: var(--f-ui); font-weight: 600; font-size: .82rem; color: var(--accent-deep);
  letter-spacing: .02em; margin-bottom: 6px;
}
.note.is-refusal { border-left-color: var(--boundary); }
.note.is-refusal .note-t { color: var(--boundary); }
.note code { background: var(--panel-2); padding: 1px 5px; border-radius: 4px; }

/* a ledger line: what an assumption cost, in axiom's own layout */
.ledger { display: grid; gap: 10px; margin: 0 0 20px; }
.ledger-row {
  display: grid; grid-template-columns: auto 1fr auto; gap: 14px; align-items: baseline;
  padding: 13px 16px; background: var(--panel); border: 1px solid var(--rule);
  border-radius: 10px;
}
.ledger-f {
  font-family: var(--f-mono); font-size: .72rem; color: var(--accent); font-weight: 500;
  white-space: nowrap;
}
.ledger-s { font-family: var(--f-ui); font-size: .88rem; color: var(--ink-2); }
.ledger-s b { color: var(--ink); font-weight: 600; }
.ledger-v {
  font-family: var(--f-mono); font-size: .82rem; color: var(--ink); white-space: nowrap;
  font-variant-numeric: tabular-nums;
}
.tag {
  font-family: var(--f-mono); font-size: .66rem; letter-spacing: .07em; text-transform: uppercase;
  padding: 2px 7px; border-radius: 4px; background: var(--panel-2); color: var(--ink-3);
  border: 1px solid var(--rule); white-space: nowrap;
}
.tag.is-warn { color: var(--warn); border-color: color-mix(in srgb, var(--warn) 40%, var(--rule)); }
.tag.is-good { color: var(--good); border-color: color-mix(in srgb, var(--good) 40%, var(--rule)); }
.tag.is-bad { color: var(--boundary); border-color: color-mix(in srgb, var(--boundary) 40%, var(--rule)); }

/* A three-column row with two nowrap edges has a min-content width that a phone
   cannot hold. Below the fold-point it stacks instead of forcing a sideways scroll. */
@media (max-width: 620px) {
  .ledger-row { grid-template-columns: 1fr; gap: 7px; }
  .ledger-f, .ledger-v { white-space: normal; }
  .ledger-v { font-size: .78rem; color: var(--ink-2); }
  .tag { white-space: normal; }
}

/* -- rule strip (the six commitments) -------------------------------------- */

.rules { display: grid; gap: 1px; background: var(--rule); border: 1px solid var(--rule);
  border-radius: 12px; overflow: hidden; }
.rule-i { background: var(--panel); padding: 22px 24px; display: grid;
  grid-template-columns: 44px 1fr; gap: 20px; align-items: start; }
.rule-n {
  font-family: var(--f-mono); font-size: .95rem; font-weight: 600; color: var(--accent);
  padding-top: 2px;
}
.rule-i h4 { margin-bottom: 6px; }
.rule-i p { font-size: .92rem; color: var(--ink-2); margin: 0; }
.rule-i p + p { margin-top: 8px; }
.rule-proof {
  font-family: var(--f-mono); font-size: .74rem; color: var(--ink-3);
  border-top: 1px dashed var(--rule); padding-top: 9px; margin-top: 11px !important;
}
@media (max-width: 620px) { .rule-i { grid-template-columns: 1fr; gap: 6px; } }

/* -- layering diagram ------------------------------------------------------ */

.layers { display: grid; gap: 10px; font-family: var(--f-ui); }
.layer {
  display: grid; grid-template-columns: 128px 1fr; gap: 16px; align-items: center;
  padding: 12px 16px; background: var(--panel); border: 1px solid var(--rule);
  border-radius: 10px;
}
.layer-n {
  font-family: var(--f-mono); font-size: .7rem; letter-spacing: .09em; text-transform: uppercase;
  color: var(--ink-3);
}
.layer-p { display: flex; flex-wrap: wrap; gap: 7px; }
.pkg {
  font-family: var(--f-mono); font-size: .78rem; padding: 3px 10px; border-radius: 6px;
  background: var(--panel-2); color: var(--ink-2); border: 1px solid var(--rule-2);
  text-decoration: none;
}
a.pkg:hover { border-color: var(--accent); color: var(--ink); }
.pkg b { color: var(--ink-3); font-weight: 400; font-size: .9em; margin-left: 5px; }
.layer-arrow { text-align: center; color: var(--ink-3); font-family: var(--f-mono); font-size: .8rem; }
@media (max-width: 620px) { .layer { grid-template-columns: 1fr; gap: 8px; } }

/* -- API explorer ---------------------------------------------------------- */

.api-search {
  display: flex; gap: 12px; align-items: center; flex-wrap: wrap; margin-bottom: 26px;
}
.api-search input {
  flex: 1 1 260px; font-family: var(--f-mono); font-size: .88rem; padding: 11px 14px;
  border: 1px solid var(--rule); border-radius: 9px; background: var(--panel);
  color: var(--ink);
}
.api-search input::placeholder { color: var(--ink-3); }
.api-count { font-family: var(--f-mono); font-size: .78rem; color: var(--ink-3); }

.api-pkg { border-top: 1px solid var(--rule-2); padding: 22px 0; }
.api-pkg[hidden] { display: none; }
.api-h { display: flex; align-items: baseline; gap: 12px; flex-wrap: wrap; margin-bottom: 4px; }
.api-h h3 { font-family: var(--f-mono); font-size: 1.05rem; letter-spacing: -.01em; }
.api-h .tag { text-transform: none; letter-spacing: .03em; }
.api-pkg p { font-size: .92rem; color: var(--ink-2); max-width: var(--measure); margin-bottom: 14px; }
.api-syms { display: flex; flex-wrap: wrap; gap: 6px; align-items: flex-start; }

/* A symbol is a chip until you open it, then it takes the full row and shows
   its signature, its one-line docstring, and a real call lifted from the
   notebook that demonstrates it. */
.sym {
  font-family: var(--f-mono); font-size: .76rem; border-radius: 5px;
  background: var(--panel); color: var(--ink-2); border: 1px solid var(--rule-2);
}
.sym > summary {
  padding: 3px 9px; cursor: pointer; display: flex; gap: 7px; align-items: baseline;
  list-style: none;
}
.sym > summary::-webkit-details-marker { display: none; }
.sym > summary::marker { content: ""; }
.sym:hover { border-color: var(--accent); color: var(--ink); }
.sym[open] {
  flex: 1 1 100%; background: var(--panel-2); border-color: var(--rule);
  box-shadow: var(--shadow);
}
.sym[open] > summary { border-bottom: 1px solid var(--rule-2); padding: 7px 12px; }
.sym[open] .sym-n { color: var(--ink); font-weight: 600; }
.sym-t { font-size: .66rem; color: var(--ink-3); letter-spacing: .04em; }
.sym-b { padding: 12px; }
.sym-sig {
  font-family: var(--f-mono); font-size: .78rem; line-height: 1.6; color: var(--ink);
  white-space: pre-wrap; overflow-wrap: anywhere; margin: 0 0 10px;
}
.sym-d {
  font-family: var(--f-ui); font-size: .85rem; line-height: 1.55; color: var(--ink-2);
  max-width: var(--measure); margin: 0 0 12px;
}
.sym-none {
  font-family: var(--f-ui); font-size: .8rem; color: var(--ink-3);
  max-width: var(--measure); margin: 0;
}
.sym-b .code { margin: 0; box-shadow: none; }
.sym-b .code-h a { color: var(--ink-3); }
.sym-b .code-h a:hover { color: var(--accent); }
.sym.hit { background: var(--accent-wash); color: var(--ink); border-color: var(--accent); }
.sym[hidden] { display: none; }

/* -- examples -------------------------------------------------------------- */

.ex-list { display: grid; gap: 14px; }
.ex {
  background: var(--panel); border: 1px solid var(--rule); border-radius: 12px;
  overflow: hidden; scroll-margin-top: 80px;
}
.ex-head { padding: 22px 24px 18px; }
.ex-n {
  font-family: var(--f-mono); font-size: .7rem; color: var(--accent); font-weight: 600;
  letter-spacing: .1em; margin-bottom: 10px;
}
.ex-head h3 { margin-bottom: 8px; }
.ex-q { font-size: .95rem; color: var(--ink-2); margin-bottom: 14px; max-width: var(--measure); }
.ex-meta { display: flex; flex-wrap: wrap; gap: 6px; }

.ex-more { border-top: 1px solid var(--rule-2); }
.ex-more > summary {
  cursor: pointer; padding: 13px 24px; list-style: none;
  font-family: var(--f-ui); font-size: .85rem; font-weight: 500; color: var(--ink-2);
  display: flex; align-items: center; gap: 9px;
}
.ex-more > summary::-webkit-details-marker { display: none; }
.ex-more > summary::before {
  content: "+"; font-family: var(--f-mono); font-size: 1rem; color: var(--accent);
  width: 14px; flex: none;
}
.ex-more[open] > summary::before { content: "\2212"; }
.ex-more > summary:hover { color: var(--ink); background: var(--panel-2); }
.ex-body { padding: 4px 24px 24px; }
.ex-framing {
  max-width: var(--measure); margin-bottom: 20px; font-size: .95rem; color: var(--ink-2);
}
.ex-framing p { white-space: pre-line; margin-bottom: .9em; }
.ex-body .code pre, .ex-body .out pre { max-height: 460px; overflow: auto; }

@media (max-width: 560px) {
  .ex-head { padding: 18px 16px 14px; }
  .ex-more > summary { padding: 12px 16px; }
  .ex-body { padding: 4px 16px 18px; }
}

/* -- walkthroughs: one example, step by step ------------------------------- */

/* A step is a two-column argument: the reasoning on the left, the code and what
   it produced on the right. Below the breakpoint it becomes reasoning-then-
   evidence, which is the order it should be read in anyway. */
.wt-step { padding-block: clamp(40px, 5.5vw, 76px); scroll-margin-top: 72px; }
.wt-step .wrap {
  display: grid; grid-template-columns: minmax(0, 4fr) minmax(0, 8fr);
  gap: clamp(24px, 3vw, 44px); align-items: start;
}
.wt-head { position: sticky; top: 76px; }
.wt-n {
  font-family: var(--f-mono); font-size: .72rem; color: var(--accent); font-weight: 600;
  letter-spacing: .12em; text-transform: uppercase; margin-bottom: 12px;
}
.wt-n span { color: var(--ink-3); font-weight: 400; }
.wt-head h2 { font-size: clamp(1.5rem, 2.4vw, 2rem); margin-bottom: 16px; }
.wt-why p { font-size: .97rem; color: var(--ink-2); margin-bottom: 16px; }
.wt-body { display: grid; gap: 20px; min-width: 0; }
.wt-body .fig, .wt-body .out, .wt-body .code, .wt-body .tbl-wrap { margin: 0; }
/* A hundred-character line has to fit the narrower of the two columns, so the
   mono size steps down a little here rather than every code block scrolling. */
.wt-body .code pre, .wt-body .out pre {
  max-height: 560px; overflow: auto; font-size: .74rem; line-height: 1.65;
}
.wt-body .prose p { font-size: .95rem; color: var(--ink-2); margin: 0; }

/* The alternative that was rejected. Deliberately not the accent colour: it is
   not the path taken, and colouring it like the argument would say it was. */
.note.is-alt { border-left-color: var(--ink-3); background: var(--panel-2); }
.note.is-alt .note-t { color: var(--ink-2); }
.note.is-alt p { font-size: .92rem; color: var(--ink-2); }

.wt-h {
  font-family: var(--f-ui); font-weight: 600; font-size: .82rem; color: var(--accent-deep);
  letter-spacing: .02em; margin-bottom: 4px;
}
.wt-framing p { font-size: .97rem; color: var(--ink-2); margin-bottom: 1em; }
.wt-framing .wt-h + p { margin-bottom: 1.4em; }

.wt-toc { display: grid; gap: 1px; background: var(--rule); border: 1px solid var(--rule);
  border-radius: 12px; overflow: hidden; margin-top: 14px; }
.wt-toc-i {
  background: var(--panel); padding: 13px 18px; display: flex; gap: 14px; align-items: baseline;
  font-family: var(--f-ui); font-size: .92rem; color: var(--ink); text-decoration: none;
}
.wt-toc-i:hover { background: var(--panel-2); color: var(--accent-deep); }
.wt-toc-n { font-family: var(--f-mono); font-size: .8rem; color: var(--accent); flex: none; }

.wt-close { background: var(--panel); }
.wt-findings p { font-size: 1.02rem; color: var(--ink-2); margin-bottom: 1.1em; }
.wt-findings p:first-child { color: var(--ink); font-size: 1.08rem; }

@media (max-width: 900px) {
  .wt-step .wrap { grid-template-columns: 1fr; }
  .wt-head { position: static; }
}

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

.foot { border-top: 1px solid var(--rule); background: var(--panel); margin-top: 40px; }
.foot-in {
  max-width: var(--wrap); margin-inline: auto; padding: 44px var(--pad);
  display: grid; gap: 18px; max-width: 1200px;
}
.foot-b { max-width: var(--measure); color: var(--ink-2); font-size: .95rem; margin: 0; }
.foot-b strong { color: var(--ink); }
.foot-s { font-family: var(--f-ui); font-size: .84rem; color: var(--ink-3); margin: 0; }
.foot-s code { font-size: .84rem; color: var(--ink-2); }

/* -- utilities ------------------------------------------------------------- */

.stack-lg > * + * { margin-top: 46px; }
.stack-lg h3 { margin-bottom: 12px; }
.stack > * + * { margin-top: 18px; }
.mt-lg { margin-top: 40px; }
.mt { margin-top: 24px; }
.grid-2 { display: grid; grid-template-columns: repeat(auto-fit, minmax(min(280px, 100%), 1fr)); gap: 22px; }
.grid-3 { display: grid; grid-template-columns: repeat(auto-fit, minmax(min(215px, 100%), 1fr)); gap: 22px; }
.muted { color: var(--ink-2); }
.small { font-size: .9rem; }
.nowrap { white-space: nowrap; }
.mono { font-family: var(--f-mono); }
.sr {
  position: absolute; width: 1px; height: 1px; padding: 0; margin: -1px;
  overflow: hidden; clip: rect(0 0 0 0); white-space: nowrap; border: 0;
}

/* -- narrow-width safety --------------------------------------------------- */
/* Long unbreakable strings — call signatures, hashes, dotted paths — are the
   usual cause of a page that scrolls sideways on a phone. Let them break. */
.stamp, .readout-d, .readout-e, .ledger-s, .note code, .ledger-s code,
.api-count, .fig-s { overflow-wrap: anywhere; }
.tbl-wrap, .chart-tbl { max-width: 100%; }
.code pre, .out pre { max-width: 100%; }
.readout-v { overflow-wrap: anywhere; }

@media (max-width: 560px) {
  body { font-size: 16px; }
  .readout-bar, .readout-e { max-width: 100%; }
  .rule-i { padding: 18px 16px; }
  .card { padding: 18px; }
  .fig { padding: 16px 14px 12px; }
}

/* ---- tutorial diagrams and equations ------------------------------------
   The diagrams are inline SVG drawn at build time from numbers the page's own
   code produced. They stroke in `currentColor` so they read on either theme;
   a hardcoded ink would vanish against the dark paper. */
.fig { margin: 32px auto; max-width: 760px; }
.fig .diagram { width: 100%; height: auto; color: var(--ink); display: block; }
.fig figcaption {
  margin-top: 10px; font-size: 0.86rem; color: var(--ink-2);
  text-align: center; line-height: 1.5;
}

/* Mathematics is marked up rather than rendered by a library: it stays
   selectable, scales with the reader's type size, and costs no request. */
.eqs { max-width: 900px; margin: 28px auto; }
.eqrow {
  display: grid; grid-template-columns: minmax(0, 1fr) minmax(0, 1.1fr);
  gap: 20px; align-items: start; margin-bottom: 22px;
}
@media (max-width: 760px) { .eqrow { grid-template-columns: 1fr; } }
.eqlabel {
  font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.06em;
  color: var(--ink-3); margin: 0 0 8px;
}
.eq {
  font-family: Georgia, "Times New Roman", serif; font-size: 1.12rem;
  line-height: 2.1; color: var(--ink); padding: 14px 16px;
  background: var(--paper); border: 1px solid var(--rule-2); border-radius: 8px;
}
.eq i { font-style: italic; }
.eq .frac { display: inline-block; vertical-align: -0.62em; text-align: center; margin: 0 0.22em; }
.eq .frac > span { display: block; padding: 0 0.35em; }
.eq .frac > span:first-child { border-bottom: 1px solid currentColor; padding-bottom: 2px; }
.eq .frac > span:last-child { padding-top: 2px; }
.eq .rad { border-top: 1px solid currentColor; padding: 0 0.2em; }
.eqcode { margin: 0; }
.eqcode pre { font-size: 0.78rem; line-height: 1.55; }