/* Percolate docs.
 *
 * Cool blue-slate ink on cool paper, verdigris as the accent -- oxidation, a
 * nod to leases that expire -- and the neutrals biased green-cool so they read
 * chosen rather than defaulted. The brand aubergine is the logo's own #350748,
 * used sparingly: the masthead rule, the active nav marker, the mark itself.
 * The site's brighter purple is deliberately absent; at documentation density
 * it competes with the accent instead of supporting it.
 *
 * Archivo for headings and labels -- industrial and sturdy. Newsreader for
 * prose, which inverts the usual sans-body and gives a reference document some
 * gravity. JetBrains Mono is a first-class voice, not a fallback: the real
 * artifacts here are psql output and YAML.
 */

:root {
  --ink:        #101519;
  --ink-2:      #38424a;   /* secondary prose, captions */
  --ink-3:      #6a757c;   /* labels, metadata */
  --paper:      #F5F7F6;
  --paper-2:    #EAEEEC;   /* evidence blocks, table stripes */
  --rule:       #D3DAD7;

  --accent:     #1B7A6E;   /* verdigris: links, proven */
  --accent-dim: #E4EFEC;
  --amber:      #9C6206;   /* designed, not run */
  --amber-dim:  #F6EEDF;
  --brick:      #A33A32;   /* absent */
  --brick-dim:  #F7E7E5;
  --brand:      #350748;   /* the logo's aubergine */
  --gold:       #9A7B1F;   /* darkened from the site's #d4af37 for AA on paper */

  --measure:    66ch;
  --wide:       96ch;

  --sans: "Archivo", ui-sans-serif, system-ui, -apple-system, "Segoe UI", sans-serif;
  --serif: "Newsreader", ui-serif, Georgia, "Times New Roman", serif;
  --mono: "JetBrains Mono", ui-monospace, "SF Mono", Menlo, Consolas, monospace;

  color-scheme: light;
}

@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --ink:        #E2E8E6;
    --ink-2:      #A9B4B1;
    --ink-3:      #7C8784;
    --paper:      #0E1315;
    --paper-2:    #171E21;
    --rule:       #2A3438;
    --accent:     #4FB3A4;
    --accent-dim: #12292A;
    --amber:      #D69A3C;
    --amber-dim:  #2A2114;
    --brick:      #D97A70;
    --brick-dim:  #2C1A19;
    --brand:      #B98BD4;   /* the aubergine lifted; #350748 is invisible here */
    --gold:       #D4AF37;
  }
}
:root[data-theme="dark"] {
  --ink: #E2E8E6; --ink-2: #A9B4B1; --ink-3: #7C8784;
  --paper: #0E1315; --paper-2: #171E21; --rule: #2A3438;
  --accent: #4FB3A4; --accent-dim: #12292A;
  --amber: #D69A3C; --amber-dim: #2A2114;
  --brick: #D97A70; --brick-dim: #2C1A19;
  --brand: #B98BD4; --gold: #D4AF37;
  color-scheme: dark;
}

* { box-sizing: border-box; }

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--serif);
  font-size: 18px;
  line-height: 1.65;
  font-variant-numeric: oldstyle-nums;
  -webkit-font-smoothing: antialiased;
}

/* ---------------------------------------------------------------- masthead */
.masthead {
  border-bottom: 1px solid var(--rule);
  background: var(--paper);
}
.masthead::before {           /* the one place the brand colour is structural */
  content: ""; display: block; height: 3px;
  background: linear-gradient(90deg, var(--brand) 0%, var(--brand) 38%, var(--accent) 38%, var(--accent) 100%);
}
.masthead-inner {
  max-width: var(--wide); margin: 0 auto; padding: 14px 24px;
  display: flex; align-items: center; gap: 12px;
}
.masthead img { width: 26px; height: 26px; display: block; }
.masthead a.wordmark {
  font-family: var(--sans); font-weight: 600; font-size: 17px;
  letter-spacing: -0.01em; color: var(--ink); text-decoration: none;
}
.masthead .tagline {
  font-family: var(--sans); font-size: 13px; color: var(--ink-3);
  border-left: 1px solid var(--rule); padding-left: 12px;
}
.masthead .spacer { flex: 1; }
.masthead .ext {
  font-family: var(--sans); font-size: 13px; color: var(--ink-2);
  text-decoration: none; border-bottom: 1px solid var(--rule);
}
.masthead .ext:hover { color: var(--accent); border-color: var(--accent); }

/* ------------------------------------------------------------------ layout */
.shell {
  max-width: var(--wide); margin: 0 auto; padding: 0 24px;
  display: grid; grid-template-columns: 220px minmax(0, 1fr); gap: 48px;
}
@media (max-width: 900px) { .shell { grid-template-columns: 1fr; gap: 0; } }

/* Sticky AND scrollable. Sticky alone was the bug: the nav is taller than a
 * laptop viewport, so pinning it at top:0 put its last section permanently
 * below the fold with no way to reach it -- the page scrolls, the pinned
 * element does not. max-height plus overflow gives the nav its own scroll, so
 * every entry is reachable from anywhere on the page. dvh after vh because
 * mobile browsers count the collapsing address bar in vh; the vh line stays as
 * the fallback for anything that does not know dvh. */
nav.toc {
  padding: 36px 0; align-self: start; position: sticky; top: 0;
  max-height: 100vh;
  max-height: 100dvh;
  overflow-y: auto;
  overscroll-behavior: contain;
  scrollbar-width: thin;
  scrollbar-color: var(--rule) transparent;
}
nav.toc::-webkit-scrollbar { width: 6px; }
nav.toc::-webkit-scrollbar-thumb { background: var(--rule); border-radius: 3px; }
nav.toc::-webkit-scrollbar-track { background: transparent; }
@media (max-width: 900px) {
  nav.toc {
    position: static; border-bottom: 1px solid var(--rule); padding-bottom: 20px;
    max-height: none; overflow-y: visible;
  }
}
nav.toc .group {
  font-family: var(--sans); font-size: 11px; font-weight: 600;
  letter-spacing: 0.09em; text-transform: uppercase; color: var(--ink-3);
  margin: 22px 0 8px;
}
nav.toc .group:first-child { margin-top: 0; }
nav.toc a {
  display: block; font-family: var(--sans); font-size: 14.5px;
  color: var(--ink-2); text-decoration: none;
  padding: 3px 0 3px 12px; border-left: 2px solid var(--rule);
}
nav.toc a:hover { color: var(--accent); border-left-color: var(--accent); }
nav.toc a.here {
  color: var(--ink); font-weight: 600;
  border-left-color: var(--brand);      /* the brand marks WHERE YOU ARE */
}

/* Prose at 66ch; evidence breaks out wider. A grid rather than negative
 * margins, so a wide table centres against the text column instead of
 * overhanging one side of it. */
main {
  padding: 40px 0 80px;
  display: grid;
  grid-template-columns: [full-start] 1fr [text-start] minmax(0, var(--measure)) [text-end] 1fr [full-end];
}
main > * { grid-column: text; min-width: 0; }
main > pre,
main > table,
main > .evidence,
main > figure.film,
main > .wide { grid-column: full; justify-self: stretch; }

/* ------------------------------------------------------------------- type */
h1, h2, h3, h4 {
  font-family: var(--sans); font-weight: 600; letter-spacing: -0.015em;
  line-height: 1.2; color: var(--ink);
}
h1 { font-size: 34px; margin: 0 0 6px; }
h2 { font-size: 23px; margin: 44px 0 12px; padding-top: 18px; border-top: 1px solid var(--rule); }
h3 { font-size: 18px; margin: 30px 0 8px; }
h4 { font-size: 15px; margin: 24px 0 6px; color: var(--ink-2); }
p, ul, ol { margin: 0 0 18px; }
li { margin-bottom: 6px; }
a { color: var(--accent); text-decoration: none; border-bottom: 1px solid var(--accent-dim); }
a:hover { border-bottom-color: var(--accent); }
strong { font-weight: 600; }
hr { border: 0; border-top: 1px solid var(--rule); margin: 36px 0; }

blockquote {
  margin: 0 0 18px; padding: 2px 0 2px 18px;
  border-left: 2px solid var(--brand); color: var(--ink-2);
}

.lede { font-size: 20px; color: var(--ink-2); margin-bottom: 26px; }

/* -------------------------------------------------------------- evidence */
pre {
  font-family: var(--mono); font-size: 13.5px; line-height: 1.55;
  background: var(--paper-2); border: 1px solid var(--rule);
  border-radius: 3px; padding: 14px 16px; overflow-x: auto;
  margin: 0 0 20px; tab-size: 2;
}
code {
  font-family: var(--mono); font-size: 0.86em;
  background: var(--paper-2); padding: 1px 5px; border-radius: 2px;
}
pre code { background: none; padding: 0; font-size: inherit; }

/* A captured terminal session, as opposed to a code sample. Different thing,
 * so it looks different: this is output, not something you type. */
.evidence {
  margin: 0 0 22px; border: 1px solid var(--rule); border-radius: 3px;
  overflow: hidden; background: var(--paper-2);
}
.evidence > .label {
  font-family: var(--sans); font-size: 11px; font-weight: 600;
  letter-spacing: 0.08em; text-transform: uppercase; color: var(--ink-3);
  padding: 7px 14px; border-bottom: 1px solid var(--rule);
  background: var(--paper);
}
.evidence pre { border: 0; border-radius: 0; margin: 0; background: none; }

table {
  border-collapse: collapse; width: 100%; margin: 0 0 22px;
  font-family: var(--sans); font-size: 14.5px;
}
th, td {
  text-align: left; padding: 8px 12px; border-bottom: 1px solid var(--rule);
  vertical-align: top;
}
th {
  font-size: 11px; font-weight: 600; letter-spacing: 0.07em;
  text-transform: uppercase; color: var(--ink-3);
  border-bottom: 1px solid var(--ink-3);
}
tbody tr:nth-child(even) { background: var(--paper-2); }
td code { background: none; padding: 0; }

/* ------------------------------------------------------------------ steps */
/* Numbered markers, for the rare list that is genuinely sequential. */
ol.steps { list-style: none; counter-reset: step; padding: 0; }
ol.steps > li {
  counter-increment: step; position: relative;
  padding-left: 40px; margin-bottom: 18px;
}
ol.steps > li::before {
  content: counter(step); position: absolute; left: 0; top: 1px;
  width: 26px; height: 26px; border-radius: 50%;
  background: var(--brand); color: #fff;
  font-family: var(--mono); font-size: 13px; font-weight: 500;
  display: flex; align-items: center; justify-content: center;
}

/* ----------------------------------------------------------------- footer */
.pager {
  display: flex; justify-content: space-between; gap: 16px;
  margin-top: 56px; padding-top: 20px; border-top: 1px solid var(--rule);
  font-family: var(--sans); font-size: 14px;
}
.pager a { border: 0; }
.pager .dir {
  display: block; font-size: 11px; letter-spacing: 0.08em;
  text-transform: uppercase; color: var(--ink-3);
}
footer.site {
  border-top: 1px solid var(--rule); margin-top: 60px;
  font-family: var(--sans); font-size: 13px; color: var(--ink-3);
}
footer.site .inner {
  max-width: var(--wide); margin: 0 auto; padding: 20px 24px;
  display: flex; gap: 18px; align-items: center; flex-wrap: wrap;
}
footer.site a { color: var(--ink-2); border: 0; }
footer.site a:hover { color: var(--accent); }
footer.site .dot { color: var(--gold); }

/* ------------------------------------------------------- why it works */
/* The third beat of every unit on this site: lesson, example, then the
 * mechanism -- collapsed, because a reader who is copying the example should
 * not have to scroll past the reasoning to reach the next one, and a reader
 * who wants the reasoning always knows where it is.
 *
 * Quiet by design. It is not an admonition and it is not a warning; it is the
 * part of the page that is optional on a first pass. A left rule in the accent
 * and nothing else. */
details.why {
  margin: 0 0 26px;
  border-left: 2px solid var(--rule);
  padding-left: 18px;
}
details.why > summary {
  font-family: var(--sans);
  font-size: 14px;
  color: var(--ink-3);
  cursor: pointer;
  list-style: none;
  padding: 3px 0;
  transition: color 0.12s ease;
}
details.why > summary::-webkit-details-marker { display: none; }
details.why > summary::before {
  content: "\203A";            /* a single chevron, rotated when open */
  display: inline-block;
  width: 14px;
  color: var(--accent);
  transition: transform 0.15s ease;
}
details.why[open] > summary::before { transform: rotate(90deg); }
details.why > summary:hover { color: var(--accent); }
details.why[open] { border-left-color: var(--accent-dim); }
details.why[open] > summary { color: var(--ink-2); margin-bottom: 8px; }
details.why > :not(summary) { font-size: 17px; }
details.why > p:last-child { margin-bottom: 12px; }
/* Keyboard users get the same affordance the pointer does. */
details.why > summary:focus-visible {
  outline: 2px solid var(--accent);
  outline-offset: 3px;
  border-radius: 2px;
}
@media (prefers-reduced-motion: reduce) {
  details.why > summary,
  details.why > summary::before { transition: none; }
}

/* The related-links line that closes a why-it-works block. Backlinks are a
 * requirement of the format rather than a courtesy: a reader who opened the
 * mechanism is the reader most likely to want the next level down. */
.related {
  font-family: var(--sans);
  font-size: 13px;
  color: var(--ink-3);
  margin-top: 14px;
}
.related strong {
  text-transform: uppercase;
  letter-spacing: 0.07em;
  font-size: 11px;
  font-weight: 600;
  color: var(--ink-3);
  margin-right: 8px;
}

/* --------------------------------------------------------------- goal line */
/* Opens every worked example: one sentence saying what we are trying to do,
 * in the same voice on every page, so an example can be recognised as an
 * example before it is read. */
p.goal {
  font-family: var(--sans);
  font-size: 15.5px;
  color: var(--ink-2);
  margin-bottom: 14px;
}

/* ------------------------------------------------------- syntax highlight */
/* Pygments, restrained: three weights of ink plus the accent. Colour here
 * competes with the status chips, which carry real meaning, so it stays quiet. */
.hl .k, .hl .kd, .hl .kn, .hl .kr, .hl .kt { color: var(--brand); font-weight: 600; }
.hl .s, .hl .s1, .hl .s2, .hl .sb, .hl .sd { color: var(--accent); }
.hl .c, .hl .c1, .hl .cm, .hl .ch          { color: var(--ink-3); font-style: italic; }
.hl .mi, .hl .mf, .hl .m                   { color: var(--gold); }
.hl .nf, .hl .nb                           { color: var(--ink); font-weight: 600; }
.hl .nt                                    { color: var(--brand); }
.hl .na                                    { color: var(--ink-2); }
.hl .o, .hl .p                             { color: var(--ink-2); }
.hl .err                                   { color: var(--brick); }
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) .hl .k { font-weight: 500; }
}

/* ---- claim ids: a reference line, not part of the reading experience ---- */
.claims{margin:56px 0 0; padding-top:14px; border-top:1px solid var(--rule,#d9e0e7);
  font-size:.68rem; line-height:1.9; color:var(--ink-3,#69757f)}
.claims a{color:inherit; text-decoration:underline; text-underline-offset:2px}
.claims a:hover{color:var(--accent,#2f5d7c)}
.claim-id{font-family:"IBM Plex Mono",ui-monospace,Menlo,monospace; white-space:nowrap;
  margin-left:.5em; opacity:.75}
.claim-id em{font-style:normal; opacity:.7; margin-left:.35em}

/* ------------------------------------------------------------------- film */
figure.film { margin: 4px 0 26px; }
figure.film video {
  display: block; width: 100%; height: auto;
  border: 1px solid var(--rule); border-radius: 4px;
  background: #0B0E10;
}
figure.film figcaption {
  font-family: var(--sans); font-size: 12.5px; color: var(--ink-3);
  margin-top: 9px;
}
figure.film figcaption a { color: var(--ink-3); border-bottom: 1px solid var(--rule); text-decoration: none; }
figure.film figcaption a:hover { color: var(--accent); border-color: var(--accent); }