/* ============================================================
   Book chapters: long-form reading. Builds on site.css tokens.
   ============================================================ */

body.chapter { background: var(--bg); }
body.chapter::after { opacity: .12; }        /* calm the grain down for reading */

.ch-wrap { max-width: 78rem; margin-inline: auto; padding-inline: clamp(1.1rem, 4vw, 2.5rem); }

/* ---------- top bar ---------- */
.ch-bar {
  position: sticky; top: 0; z-index: 40;
  backdrop-filter: blur(16px) saturate(160%);
  -webkit-backdrop-filter: blur(16px) saturate(160%);
  background: color-mix(in oklab, var(--bg) 82%, transparent);
  border-bottom: 1px solid var(--line);
}
.ch-bar .ch-wrap { display: flex; align-items: center; gap: 1rem; height: 56px; }
.ch-bar .part {
  font-family: var(--mono); font-size: .64rem; letter-spacing: .14em;
  text-transform: uppercase; color: var(--mut);
  white-space: nowrap; overflow: hidden; text-overflow: ellipsis;
}
.ch-bar .sp { margin-left: auto; }
.ch-bar a.mini {
  display: inline-flex; align-items: center; gap: .4rem;
  font-size: .8rem; color: var(--ink-2); white-space: nowrap;
  padding: .35rem .75rem; border-radius: 100px;
  border: 1px solid var(--line); background: var(--card);
  transition: background .2s, color .2s, border-color .2s;
}
.ch-bar a.mini:hover { background: var(--card-2); color: var(--ink); border-color: var(--line-2); }
@media (max-width: 640px) { .ch-bar .part { display: none; } }

/* ---------- reading column ---------- */
.ch-body { padding-block: clamp(2rem, 5vw, 3.5rem) 5rem; }
.ch-col { max-width: 40rem; margin-inline: auto; }

.ch-col h1 {
  font-size: clamp(2rem, 5vw, 3rem);
  margin-bottom: 2rem; letter-spacing: -.03em;
}
.ch-col h1 .num {
  display: block; font-family: var(--mono); font-size: .72rem;
  letter-spacing: .16em; text-transform: uppercase; color: var(--acid);
  margin-bottom: .8rem; font-weight: 600;
}
.ch-col h2 {
  font-size: clamp(1.35rem, 2.6vw, 1.75rem);
  margin: 3rem 0 1rem; padding-top: 1.6rem;
  border-top: 1px solid var(--line);
}
.ch-col h3 { font-size: 1.12rem; margin: 2.1rem 0 .7rem; }
.ch-col h4 { font-size: 1rem; margin: 1.6rem 0 .5rem; color: var(--ink-2); }

.ch-col p { margin: 0 0 1.15rem; font-size: 1.02rem; line-height: 1.72; color: var(--ink-2); }
.ch-col strong { color: var(--ink); font-weight: 650; }
.ch-col em { color: var(--ink); }

.ch-col a { color: var(--acid); text-decoration: underline; text-underline-offset: 2px;
  text-decoration-thickness: 1px; text-decoration-color: color-mix(in oklab, var(--acid) 45%, transparent); }
.ch-col a:hover { text-decoration-color: var(--acid); }

.ch-col ul, .ch-col ol { margin: 0 0 1.2rem; padding-left: 1.3rem; color: var(--ink-2); }
.ch-col li { margin-bottom: .45rem; line-height: 1.65; }

.ch-col blockquote {
  margin: 1.5rem 0; padding: .2rem 0 .2rem 1.1rem;
  border-left: 2px solid var(--acid); color: var(--mut); font-style: italic;
}

code, .ch-col code {
  font-family: var(--mono); font-size: .88em;
  background: var(--card-2); border: 1px solid var(--line);
  border-radius: 5px; padding: .1em .35em; color: var(--ink);
}
pre {
  overflow-x: auto; margin: 0 0 1.4rem;
  background: var(--bg-2); border: 1px solid var(--line);
  border-radius: var(--r); padding: 1rem 1.1rem;
}
pre code { background: none; border: 0; padding: 0; font-size: .85rem; line-height: 1.6; }

/* ---------- figures ---------- */
.ch-col figure { margin: 2rem 0; }
.ch-col figure img, .ch-col p > img {
  display: block; max-width: 100%; height: auto; margin-inline: auto;
  background: #fff; border-radius: 8px; padding: .75rem;
  border: 1px solid var(--line);
}
.ch-col figcaption {
  margin-top: .7rem; font-size: .84rem; color: var(--mut);
  text-align: center; line-height: 1.5;
}

/* ---------- tables ---------- */
.ch-tablewrap { overflow-x: auto; margin: 0 0 1.6rem; }
.ch-col table { border-collapse: collapse; width: 100%; font-size: .9rem; }
.ch-col th, .ch-col td {
  padding: .5rem .7rem; text-align: left;
  border-bottom: 1px solid var(--line); color: var(--ink-2);
}
.ch-col th { color: var(--ink); font-weight: 640; white-space: nowrap;
  border-bottom-color: var(--line-2); }
.ch-col caption { caption-side: bottom; margin-top: .6rem; font-size: .82rem; color: var(--mut); }

/* ---------- maths (native MathML) ---------- */
math { font-size: 1.02em; }
math[display="block"] {
  display: block; margin: 1.5rem 0; overflow-x: auto; overflow-y: hidden;
  text-align: center;
}

/* ---------- chapter nav ---------- */
.ch-nav {
  display: grid; grid-template-columns: 1fr 1fr; gap: .8rem;
  margin-top: 4rem; padding-top: 2rem; border-top: 1px solid var(--line);
}
.ch-nav a {
  display: block; padding: 1rem 1.1rem; border-radius: var(--r);
  border: 1px solid var(--line); background: var(--card);
  text-decoration: none;
  transition: border-color .2s, background .2s, transform .2s;
}
.ch-nav a:hover { border-color: var(--line-2); background: var(--card-2); transform: translateY(-2px); }
.ch-nav span { display: block; font-family: var(--mono); font-size: .64rem;
  letter-spacing: .13em; text-transform: uppercase; color: var(--mut); margin-bottom: .3rem; }
.ch-nav b { font-size: .93rem; font-weight: 620; color: var(--ink); letter-spacing: -.01em; }
.ch-nav .next { text-align: right; }
.ch-nav .empty { visibility: hidden; }
@media (max-width: 560px) { .ch-nav { grid-template-columns: 1fr; } .ch-nav .next { text-align: left; } }

/* ---------- contents page ---------- */
.toc-part { margin-bottom: 2.6rem; }
.toc-part > h2 {
  font-size: clamp(1.3rem, 3vw, 1.7rem); margin-bottom: .3rem;
}
.toc-part > .rn {
  font-family: var(--mono); font-size: .66rem; letter-spacing: .16em;
  text-transform: uppercase; color: var(--acid); display: block; margin-bottom: .5rem;
}
.toc-list { list-style: none; margin: 1rem 0 0; padding: 0; display: grid; gap: .35rem; }
.toc-list a {
  display: flex; align-items: baseline; gap: .8rem;
  padding: .65rem .9rem; border-radius: var(--r);
  border: 1px solid transparent; text-decoration: none;
  transition: background .2s, border-color .2s, transform .2s;
}
.toc-list a:hover { background: var(--card-2); border-color: var(--line); transform: translateX(3px); }
.toc-list .n { font-family: var(--mono); font-size: .72rem; color: var(--mut); flex: none; width: 1.6rem; }
.toc-list .t { font-weight: 550; font-size: .96rem; color: var(--ink); }
.toc-list .pg { margin-left: auto; font-family: var(--mono); font-size: .72rem; color: var(--mut); flex: none; }
.toc-note {
  margin-top: .5rem; padding: .8rem 1rem; border-radius: var(--r);
  border: 1px solid var(--line); border-left: 2px solid var(--acid);
  background: var(--card); font-size: .85rem; color: var(--ink-2);
}

/* ============================================================
   Worked examples: inside the chapter

   The run bar sits inside a "Try it yourself" blockquote; the panel closes
   the chapter. Both point at /code/, which build-code.mjs generates.
   ============================================================ */

.ch-col a.ch-code { text-decoration: none; }
.ch-col a.ch-code code {
  color: var(--acid);
  border-color: color-mix(in oklab, var(--acid) 35%, var(--line));
  transition: background .2s, border-color .2s;
}
.ch-col a.ch-code:hover code {
  background: color-mix(in oklab, var(--acid) 12%, var(--card-2));
  border-color: var(--acid);
}

.ch-col .ch-run {
  display: flex; flex-wrap: wrap; gap: .45rem .9rem;
  margin: .9rem 0 .2rem; font-style: normal;
}
.ch-run .run-item { display: inline-flex; flex-wrap: wrap; align-items: center; gap: .45rem .8rem; }
.ch-run .run-item b {
  font-family: var(--mono); font-size: .72rem; color: var(--mut);
  font-weight: 500; letter-spacing: -.01em;
}
.ch-col .ch-run a {
  font-size: .78rem; text-decoration: none; color: var(--ink-2);
  padding: .3rem .7rem; border-radius: 100px;
  border: 1px solid var(--line); background: var(--card);
  transition: background .2s, border-color .2s, color .2s;
}
.ch-col .ch-run a:hover { background: var(--card-2); border-color: var(--line-2); color: var(--ink); }
.ch-col .ch-run a.run-go {
  color: var(--acid); border-color: color-mix(in oklab, var(--acid) 40%, transparent);
}
.ch-col .ch-run a.run-go:hover { background: color-mix(in oklab, var(--acid) 14%, transparent); }

.ch-code-panel { margin-top: 3.5rem; padding-top: 1.6rem; border-top: 1px solid var(--line); }
.ch-code-panel > h2 { border: 0; padding-top: 0; margin: 0 0 .6rem; font-size: 1.35rem; }
.ch-code-panel > p { color: var(--mut); font-size: .92rem; }
.ch-code-panel ul { list-style: none; margin: 1.2rem 0 0; padding: 0; display: grid; gap: .7rem; }
.ch-code-panel li {
  padding: 1rem 1.1rem; border-radius: var(--r);
  border: 1px solid var(--line); background: var(--card);
}
.ch-code-panel .cp-name { display: flex; align-items: baseline; gap: .7rem; flex-wrap: wrap; text-decoration: none; }
.ch-code-panel .cp-name code { font-size: .78rem; color: var(--acid); }
.ch-code-panel .cp-name span { font-weight: 620; color: var(--ink); font-size: .98rem; }
.ch-code-panel li p { margin: .5rem 0 .7rem; font-size: .89rem; line-height: 1.6; color: var(--ink-2); }
.ch-code-panel .cp-links { display: flex; flex-wrap: wrap; align-items: center; gap: .4rem .85rem; }
.ch-code-panel .cp-needs {
  font-family: var(--mono); font-size: .7rem; color: var(--mut);
  padding: .25rem .55rem; border-radius: 5px; background: var(--card-2);
}
.ch-code-panel .cp-links a {
  font-size: .78rem; text-decoration: none; color: var(--ink-2);
  padding: .3rem .7rem; border-radius: 100px;
  border: 1px solid var(--line); background: var(--card);
}
.ch-code-panel .cp-links a:first-of-type {
  color: var(--acid); border-color: color-mix(in oklab, var(--acid) 40%, transparent);
}
.ch-code-panel .cp-links a:hover { background: var(--card-2); border-color: var(--line-2); }
.ch-code-panel + .ch-nav { margin-top: 2.4rem; }