/* ============ The Illustrated Book of LLMs — shared styles ============ */
:root {
  --bg: #fbfaf7;
  --bg-elev: #ffffff;
  --bg-soft: #f3f1ec;
  --fg: #1d1d1f;
  --fg-soft: #55565b;
  --fg-faint: #8a8b90;
  --border: #e4e1da;
  --accent: #5b5bd6;        /* indigo */
  --accent-soft: #ecebfb;
  --c1: #5b5bd6;            /* series colors (use for charts) */
  --c2: #e5484d;
  --c3: #12a594;
  --c4: #f5a524;
  --c5: #8e4ec6;
  --c6: #0090ff;
  --good: #12a594;
  --bad: #e5484d;
  --warn: #f5a524;
  --code-bg: #f6f5f1;
  --shadow: 0 1px 2px rgba(0,0,0,.04), 0 4px 16px rgba(0,0,0,.05);
  --radius: 12px;
  --sidebar-w: 270px;
  --toc-w: 220px;
  --content-w: 760px;
  --font: "Inter", -apple-system, BlinkMacSystemFont, "Segoe UI", Roboto, sans-serif;
  --font-serif: "Source Serif 4", Georgia, serif;
  --mono: "JetBrains Mono", ui-monospace, SFMono-Regular, Menlo, monospace;
}
[data-theme="dark"] {
  --bg: #141416;
  --bg-elev: #1c1c1f;
  --bg-soft: #232327;
  --fg: #ececee;
  --fg-soft: #b0b0b7;
  --fg-faint: #7c7c85;
  --border: #2e2e33;
  --accent: #8b8cf6;
  --accent-soft: #26264a;
  --c1: #8b8cf6;
  --c2: #ff6b70;
  --c3: #2ed3b7;
  --c4: #ffc53d;
  --c5: #c084fc;
  --c6: #4cb3ff;
  --code-bg: #1f1f23;
  --shadow: 0 1px 2px rgba(0,0,0,.3), 0 4px 16px rgba(0,0,0,.3);
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; scroll-padding-top: 72px; }
body {
  margin: 0; background: var(--bg); color: var(--fg);
  font-family: var(--font); font-size: 17px; line-height: 1.7;
  -webkit-font-smoothing: antialiased;
}
a { color: var(--accent); text-decoration: none; }
a:hover { text-decoration: underline; }

/* ---------- top bar ---------- */
.topbar {
  position: sticky; top: 0; z-index: 50; height: 56px;
  display: flex; align-items: center; gap: 12px; padding: 0 20px;
  background: color-mix(in srgb, var(--bg) 85%, transparent);
  backdrop-filter: blur(10px); border-bottom: 1px solid var(--border);
}
.topbar .brand { font-weight: 700; color: var(--fg); letter-spacing: -.01em; }
.topbar .brand span { color: var(--accent); }
.topbar .spacer { flex: 1; }
.topbar button, .icon-btn {
  background: var(--bg-soft); border: 1px solid var(--border); color: var(--fg);
  border-radius: 8px; padding: 6px 10px; cursor: pointer; font: inherit; font-size: 14px;
}
.topbar button:hover { border-color: var(--accent); }
#menu-btn { display: none; }
.progress-bar { position: absolute; left: 0; bottom: -1px; height: 2px; background: var(--accent); width: 0; transition: width .1s; }

/* ---------- layout ---------- */
.layout { display: grid; grid-template-columns: var(--sidebar-w) minmax(0,1fr) var(--toc-w); }
.sidebar {
  position: sticky; top: 56px; height: calc(100vh - 56px); overflow-y: auto;
  padding: 20px 14px 40px; border-right: 1px solid var(--border); font-size: 14.5px;
}
.sidebar .ch { display: flex; gap: 10px; align-items: baseline; padding: 7px 10px; border-radius: 8px; color: var(--fg-soft); }
.sidebar .ch:hover { background: var(--bg-soft); text-decoration: none; color: var(--fg); }
.sidebar .ch.active { background: var(--accent-soft); color: var(--accent); font-weight: 600; }
.sidebar .ch .num { font-family: var(--mono); font-size: 12px; opacity: .7; min-width: 18px; }
.sidebar .sec-label { font-size: 11.5px; text-transform: uppercase; letter-spacing: .08em; color: var(--fg-faint); margin: 18px 10px 6px; }
.toc { position: sticky; top: 56px; height: calc(100vh - 56px); overflow-y: auto; padding: 28px 16px; font-size: 13.5px; }
.toc .toc-title { font-size: 11.5px; text-transform: uppercase; letter-spacing: .08em; color: var(--fg-faint); margin-bottom: 8px; }
.toc a { display: block; color: var(--fg-faint); padding: 3px 0 3px 10px; border-left: 2px solid var(--border); line-height: 1.4; }
.toc a.h3 { padding-left: 22px; font-size: 12.5px; }
.toc a.active { color: var(--accent); border-left-color: var(--accent); }
.toc a:hover { color: var(--fg); text-decoration: none; }

main { padding: 40px 32px 120px; min-width: 0; position: relative; }
.content { max-width: var(--content-w); margin: 0 auto; }

@media (max-width: 1200px) { .layout { grid-template-columns: var(--sidebar-w) minmax(0,1fr); } .toc { display: none; } }
@media (max-width: 860px) {
  .layout { grid-template-columns: minmax(0, 1fr); }
  #menu-btn { display: inline-block; }
  .sidebar { position: fixed; left: 0; top: 56px; z-index: 40; width: 290px; background: var(--bg); transform: translateX(-100%); transition: transform .2s; }
  .sidebar.open { transform: none; box-shadow: var(--shadow); }
  main { padding: 24px 18px 100px; }
  body { font-size: 16px; }
}

/* ---------- typography ---------- */
.chapter-kicker { font-family: var(--mono); font-size: 13px; color: var(--accent); letter-spacing: .05em; text-transform: uppercase; }
h1 { font-size: 2.4em; line-height: 1.15; letter-spacing: -.025em; margin: .2em 0 .4em; }
h2 { font-size: 1.6em; letter-spacing: -.015em; margin: 2.4em 0 .6em; padding-top: .6em; border-top: 1px solid var(--border); }
h3 { font-size: 1.2em; margin: 1.8em 0 .5em; }
h4 { font-size: 1.02em; margin: 1.4em 0 .4em; }
.lede { font-size: 1.15em; color: var(--fg-soft); font-family: var(--font-serif); line-height: 1.6; }
p { margin: .8em 0; }
ul, ol { padding-left: 1.4em; }
li { margin: .25em 0; }
strong { font-weight: 650; }
hr { border: 0; border-top: 1px solid var(--border); margin: 2em 0; }
code { font-family: var(--mono); font-size: .86em; background: var(--code-bg); border: 1px solid var(--border); padding: .1em .35em; border-radius: 5px; }
pre { background: var(--code-bg); border: 1px solid var(--border); border-radius: var(--radius); padding: 14px 16px; overflow-x: auto; font-size: 13.5px; line-height: 1.55; }
pre code { background: none; border: 0; padding: 0; font-size: inherit; }
.katex-display { overflow-x: auto; overflow-y: hidden; padding: .3em 0; }
table { border-collapse: collapse; width: 100%; font-size: .92em; margin: 1em 0; }
th, td { border-bottom: 1px solid var(--border); padding: 8px 10px; text-align: left; vertical-align: top; }
th { font-weight: 600; color: var(--fg-soft); background: var(--bg-soft); }
.muted { color: var(--fg-faint); }
.small { font-size: .88em; }

/* ---------- callouts ---------- */
.callout { border-radius: var(--radius); padding: 14px 18px; margin: 1.4em 0; border: 1px solid var(--border); background: var(--bg-elev); }
.callout > :first-child { margin-top: 0; } .callout > :last-child { margin-bottom: 0; }
.callout .label { display: block; font-size: 12px; font-weight: 700; letter-spacing: .07em; text-transform: uppercase; margin-bottom: 4px; }
.intuition { background: color-mix(in srgb, var(--c3) 8%, var(--bg-elev)); border-color: color-mix(in srgb, var(--c3) 30%, var(--border)); }
.intuition .label { color: var(--c3); }
.keyidea { background: color-mix(in srgb, var(--accent) 8%, var(--bg-elev)); border-color: color-mix(in srgb, var(--accent) 35%, var(--border)); }
.keyidea .label { color: var(--accent); }
.warning { background: color-mix(in srgb, var(--warn) 9%, var(--bg-elev)); border-color: color-mix(in srgb, var(--warn) 35%, var(--border)); }
.warning .label { color: color-mix(in srgb, var(--warn) 80%, var(--fg)); }
.analogy { background: color-mix(in srgb, var(--c5) 7%, var(--bg-elev)); border-color: color-mix(in srgb, var(--c5) 30%, var(--border)); }
.analogy .label { color: var(--c5); }

/* collapsible deep dive */
details.deep { border: 1px solid var(--border); border-radius: var(--radius); margin: 1.2em 0; background: var(--bg-elev); }
details.deep > summary { cursor: pointer; padding: 10px 16px; font-weight: 600; font-size: .95em; color: var(--fg-soft); list-style: none; display: flex; gap: 8px; align-items: center; }
details.deep > summary::-webkit-details-marker { display: none; }
details.deep > summary::before { content: "▸"; transition: transform .15s; color: var(--accent); }
details.deep[open] > summary::before { transform: rotate(90deg); }
details.deep > .body { padding: 0 18px 14px; border-top: 1px dashed var(--border); }

/* quiz / interview check */
.quiz { border: 1px solid var(--border); border-radius: var(--radius); padding: 14px 18px; margin: 1.6em 0; background: var(--bg-soft); }
.quiz .label { font-size: 12px; font-weight: 700; letter-spacing: .07em; text-transform: uppercase; color: var(--c2); }
.quiz .q { font-weight: 600; margin: .4em 0; }
.quiz .options { display: grid; gap: 6px; margin: 8px 0; }
.quiz .options button { text-align: left; background: var(--bg-elev); border: 1px solid var(--border); border-radius: 8px; padding: 8px 12px; color: var(--fg); font: inherit; font-size: .95em; cursor: pointer; }
.quiz .options button:hover { border-color: var(--accent); }
.quiz .options button.correct { border-color: var(--good); background: color-mix(in srgb, var(--good) 12%, var(--bg-elev)); }
.quiz .options button.wrong { border-color: var(--bad); background: color-mix(in srgb, var(--bad) 10%, var(--bg-elev)); }
.quiz .explain { display: none; font-size: .93em; color: var(--fg-soft); margin-top: 6px; }
.quiz.answered .explain { display: block; }
.quiz .reveal-btn { background: var(--bg-elev); border: 1px solid var(--border); border-radius: 8px; padding: 6px 12px; cursor: pointer; color: var(--fg); font: inherit; font-size: .9em; }

/* ---------- interactive widgets ---------- */
.widget {
  border: 1px solid var(--border); border-radius: 16px; background: var(--bg-elev);
  box-shadow: var(--shadow); padding: 18px 20px; margin: 1.8em 0;
}
.widget .w-title { font-weight: 700; font-size: .95em; display: flex; align-items: center; gap: 8px; margin-bottom: 2px; }
.widget .w-title::before { content: "◆"; color: var(--accent); font-size: .8em; }
.widget .w-sub { font-size: .87em; color: var(--fg-faint); margin-bottom: 12px; }
.widget .controls { display: flex; flex-wrap: wrap; gap: 10px 22px; align-items: center; margin: 10px 0; font-size: .9em; }
.widget .controls label { display: flex; align-items: center; gap: 8px; color: var(--fg-soft); }
.widget .controls .val { font-family: var(--mono); font-size: .9em; color: var(--fg); min-width: 3.2em; display: inline-block; }
.widget input[type=range] { accent-color: var(--accent); width: 140px; }
.widget select, .widget input[type=number], .widget input[type=text] {
  background: var(--bg-soft); color: var(--fg); border: 1px solid var(--border); border-radius: 7px; padding: 4px 8px; font: inherit; font-size: .92em;
}
.widget input[type=number] { width: 90px; }
.btn {
  background: var(--accent); color: white; border: 0; border-radius: 8px; padding: 7px 14px; font: inherit; font-size: .9em; font-weight: 600; cursor: pointer;
}
.btn:hover { filter: brightness(1.08); }
.btn.secondary { background: var(--bg-soft); color: var(--fg); border: 1px solid var(--border); }
.btn:disabled { opacity: .45; cursor: default; }
.seg { display: inline-flex; border: 1px solid var(--border); border-radius: 8px; overflow: hidden; }
.seg button { background: var(--bg-soft); color: var(--fg-soft); border: 0; padding: 5px 11px; font: inherit; font-size: .88em; cursor: pointer; border-right: 1px solid var(--border); }
.seg button:last-child { border-right: 0; }
.seg button.on { background: var(--accent); color: #fff; }
.widget canvas, .widget svg { display: block; max-width: 100%; }
.readout { font-family: var(--mono); font-size: .86em; background: var(--bg-soft); border-radius: 8px; padding: 8px 12px; margin-top: 10px; color: var(--fg-soft); white-space: pre-wrap; }
.readout b { color: var(--fg); }
.stat-row { display: flex; flex-wrap: wrap; gap: 10px; margin-top: 12px; }
.stat { flex: 1 1 140px; background: var(--bg-soft); border-radius: 10px; padding: 10px 12px; }
.stat .k { font-size: 11.5px; text-transform: uppercase; letter-spacing: .06em; color: var(--fg-faint); }
.stat .v { font-family: var(--mono); font-size: 1.15em; font-weight: 600; }
.grid-2 { display: grid; grid-template-columns: 1fr 1fr; gap: 16px; }
@media (max-width: 700px) { .grid-2 { grid-template-columns: 1fr; } }

/* ---------- figures ---------- */
figure { margin: 1.6em 0; text-align: center; }
figure img { max-width: 100%; border-radius: 10px; border: 1px solid var(--border); background: white; }
figcaption { font-size: .85em; color: var(--fg-faint); margin-top: 6px; }

/* ---------- chapter nav ---------- */
.chapter-nav { display: grid; grid-template-columns: 1fr 1fr; gap: 14px; margin-top: 80px; }
.chapter-nav a { border: 1px solid var(--border); border-radius: var(--radius); padding: 14px 18px; color: var(--fg); background: var(--bg-elev); }
.chapter-nav a:hover { border-color: var(--accent); text-decoration: none; }
.chapter-nav .dir { font-size: 12px; color: var(--fg-faint); text-transform: uppercase; letter-spacing: .06em; }
.chapter-nav .next { text-align: right; grid-column: 2; }
.chapter-nav .title { font-weight: 600; }

/* ---------- landing ---------- */
.hero { max-width: 900px; margin: 0 auto; padding: 70px 24px 30px; text-align: center; }
.hero h1 { font-size: 3.2em; }
.hero .lede { max-width: 640px; margin: 0 auto; }
.cards { max-width: 1100px; margin: 30px auto 80px; padding: 0 24px; display: grid; grid-template-columns: repeat(auto-fill, minmax(300px, 1fr)); gap: 16px; }
.card { display: block; border: 1px solid var(--border); border-radius: 16px; padding: 20px 22px; background: var(--bg-elev); color: var(--fg); transition: transform .12s, border-color .12s; }
.card:hover { transform: translateY(-2px); border-color: var(--accent); text-decoration: none; }
.card .num { font-family: var(--mono); color: var(--accent); font-size: 13px; }
.card h3 { margin: 4px 0 6px; font-size: 1.15em; }
.card p { margin: 0; font-size: .92em; color: var(--fg-soft); line-height: 1.5; }
.card .tags { margin-top: 10px; display: flex; flex-wrap: wrap; gap: 6px; }
.card .tags span { font-size: 11.5px; background: var(--bg-soft); border-radius: 99px; padding: 2px 9px; color: var(--fg-faint); }
.footer { text-align: center; color: var(--fg-faint); font-size: 13px; padding: 30px; border-top: 1px solid var(--border); }

/* tooltips for SVG widgets */
.lb-tip { position: fixed; pointer-events: none; z-index: 100; background: var(--fg); color: var(--bg); font-size: 12.5px; padding: 5px 9px; border-radius: 6px; font-family: var(--mono); opacity: 0; transition: opacity .1s; }

.hljs { background: transparent !important; padding: 0 !important; }

/* mobile: let wide tables scroll instead of widening the page */
@media (max-width: 860px) {
  .content table { display: block; overflow-x: auto; max-width: 100%; }
  .content .katex-display { max-width: 100%; }
}
@media (max-width: 860px) {
  .content code { overflow-wrap: anywhere; word-break: break-word; }
  .content svg:not(.katex svg) { max-width: 100%; height: auto; }
  .seg { flex-wrap: wrap; }
  .seg button { border-bottom: 1px solid var(--border); }
  main { overflow-x: clip; }
}