/* CCPP-I explainers: shared design. Projector-first: large type, one concept per section. */
/* Palette and type follow the IFFLab site (ifflab_web/assets/css/main.css): warm paper, blue-black ink,
   scientific teal, JetBrains Mono headings, Inter Tight body. */
:root {
  --sans: "Inter Tight", ui-sans-serif, system-ui, -apple-system, "Segoe UI", Roboto, sans-serif;
  --mono: "JetBrains Mono", ui-monospace, "SF Mono", Menlo, Consolas, monospace;
  --bg: oklch(0.985 0.006 85);
  --fg: oklch(0.20 0.02 260);
  --muted: oklch(0.48 0.015 260);
  --accent: oklch(0.52 0.12 200);
  --accent-bg: oklch(0.94 0.035 200);
  --border: oklch(0.88 0.008 260);
  --code-bg: oklch(0.955 0.006 260);
  --sel: #ffe08a;
  --sel-fg: oklch(0.20 0.02 260);
  --ok: #15803d;
  --bad: #c5221f;
  --bad-bg: #fce8e6;
  --badge-fg: #ffffff;
  --kw: oklch(0.50 0.20 295);
  --str: oklch(0.48 0.16 145);
  --num: oklch(0.55 0.18 40);
  --cmt: oklch(0.55 0.02 260);
  --fn: oklch(0.50 0.18 240);
  --c1: #fde2e4; --c2: #d7f0e2; --c3: #dbe8ff; --c4: #fff1c2;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: oklch(0.145 0.015 260); --fg: oklch(0.94 0.008 85); --muted: oklch(0.65 0.015 260);
    --accent: oklch(0.72 0.09 200); --accent-bg: oklch(0.26 0.04 200);
    --border: oklch(0.27 0.012 260); --code-bg: oklch(0.19 0.014 260); --sel: #8a6d00; --sel-fg: #ffffff;
    --ok: #6ecf86; --bad: #f28b82; --bad-bg: #3a1d1b; --badge-fg: oklch(0.145 0.015 260);
    --kw: oklch(0.78 0.16 320); --str: oklch(0.78 0.14 145); --num: oklch(0.80 0.15 65); --cmt: oklch(0.62 0.02 260); --fn: oklch(0.78 0.14 240);
    --c1: #5a2a30; --c2: #214a33; --c3: #233b66; --c4: #5a4a10;
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: oklch(0.145 0.015 260); --fg: oklch(0.94 0.008 85); --muted: oklch(0.65 0.015 260);
  --accent: oklch(0.72 0.09 200); --accent-bg: oklch(0.26 0.04 200);
  --border: oklch(0.27 0.012 260); --code-bg: oklch(0.19 0.014 260); --sel: #8a6d00; --sel-fg: #ffffff;
  --ok: #6ecf86; --bad: #f28b82; --bad-bg: #3a1d1b; --badge-fg: oklch(0.145 0.015 260);
  --kw: oklch(0.78 0.16 320); --str: oklch(0.78 0.14 145); --num: oklch(0.80 0.15 65); --cmt: oklch(0.62 0.02 260); --fn: oklch(0.78 0.14 240);
  --c1: #5a2a30; --c2: #214a33; --c3: #233b66; --c4: #5a4a10;
  color-scheme: dark;
}

* { box-sizing: border-box; }
html { scroll-behavior: smooth; font-size: 19px; }
body {
  margin: 0;
  background: var(--bg);
  color: var(--fg);
  font: 1rem/1.55 var(--sans);
  -webkit-font-smoothing: antialiased;
}
a { color: var(--accent); text-underline-offset: 3px; }
::selection { background: var(--accent); color: var(--bg); }
h1, h2 { font-family: var(--mono); font-weight: 500; letter-spacing: -0.018em; }
/* "§ 01" mono caption: the IFFLab signature label */
.caption, .out .label, .state .label, .card h4 { font-family: var(--mono); font-size: .66rem; letter-spacing: .14em; text-transform: uppercase; color: var(--muted); font-weight: 500; }
code, pre, .mono { font-family: var(--mono); }
/* students must see the characters they type: no != → ≠ ligatures */
* { font-variant-ligatures: none; }
code { background: var(--code-bg); padding: .05em .35em; border-radius: 4px; font-size: .92em; }
.muted { color: var(--muted); }

/* layout: single column + fixed toolbar */
.toolbar {
  position: fixed; top: .6rem; right: .8rem; z-index: 10;
  display: flex; gap: .4rem; align-items: center;
  background: var(--bg); border: 1px solid var(--border); border-radius: 999px; padding: .2rem .4rem;
  font-family: var(--mono); font-size: .7rem; letter-spacing: .1em; text-transform: uppercase;
  opacity: .55; transition: opacity .15s;
}
.toolbar:hover { opacity: 1; }
.toolbar button {
  background: none; color: var(--fg); border: 0; border-radius: 999px; padding: .2rem .6rem;
  font: inherit; cursor: pointer;
}
.toolbar button:hover { color: var(--accent); background: var(--accent-bg); }
.toolbar .sep { width: 1px; height: 1.1em; background: var(--border); }
.toolbar select {
  font: inherit; text-transform: none; letter-spacing: 0; color: var(--fg); background: var(--bg); border: 0; border-radius: 999px;
  padding: .2rem .4rem; max-width: 12rem; cursor: pointer;
}
.toolbar select:hover { color: var(--accent); background: var(--accent-bg); }
.toolbar .fs { font-family: var(--mono); text-transform: none; color: var(--muted); min-width: 2.2em; text-align: center; }
kbd { font: inherit; font-size: .85em; border: 1px solid var(--border); border-bottom-width: 2px; border-radius: 4px; padding: 0 .35em; }

main { max-width: 66rem; margin: 0 auto; padding: 1.5rem 2.5rem 6rem; }
header.doc { padding-bottom: 1rem; border-bottom: 1px solid var(--border); margin-bottom: 1rem; }
header.doc h1 { font-size: 2.3rem; font-weight: 450; letter-spacing: -0.025em; margin: .3rem 0 .3rem; line-height: 1.1; }
header.doc p { margin: 0; color: var(--muted); }
header.doc .keys { font-size: .75rem; margin-top: .4rem; }

section.step { padding: 2.2rem 0 2.6rem; border-bottom: 1px solid var(--border); scroll-margin-top: 1rem; }
section.step:last-child { border-bottom: 0; }
main { counter-reset: sec; }
section.step h2 { font-size: 1.45rem; margin: 0 0 .5rem; line-height: 1.25; }
@media (max-width: 110rem) { header.doc h1, section.step h2, section.pause h2 { padding-right: 21rem; } }
section.step h2::before { counter-increment: sec; content: "§ " counter(sec, decimal-leading-zero); display: block; margin-bottom: .35rem; font-size: .66rem; letter-spacing: .14em; color: var(--accent); font-weight: 500; }
section.step h2 code { font-size: .9em; }
section.step h3 { font-size: 1.05rem; margin: 1.4rem 0 .4rem; color: var(--muted); font-weight: 600; }
section.step p { margin: .3rem 0 .8rem; max-width: 62ch; }
section.step p.lead { color: var(--muted); }

section.pause { padding: 1.6rem 0 2rem; border-bottom: 1px solid var(--border); scroll-margin-top: 1rem; }
section.pause .phead { display: flex; align-items: center; gap: .8rem; flex-wrap: wrap; margin-bottom: .6rem; }
section.pause .mark { font-size: 1.5rem; }
section.pause h2 { font-size: 1.3rem; margin: 0; }
section.pause .phead .muted { font-size: .85rem; }
section.pause .ex { border-left: 3px solid var(--accent); padding: .2rem 0 .2rem 1.1rem; margin: .8rem 0; }
section.pause .ex h3 { font-size: 1rem; margin: 0 0 .3rem; font-weight: 600; }
section.pause .ex p, section.pause .ex li { max-width: 70ch; margin: .25rem 0; }
section.pause .ex ol { margin: .2rem 0 .4rem; padding-left: 1.4rem; }
section.pause .ex pre.code { margin: .4rem 0 .6rem; }
section.pause .ex pre.out { margin: .3rem 0 .4rem; }

/* code blocks */
pre.code {
  background: var(--code-bg); border: 1px solid var(--border); border-radius: 8px;
  padding: .7rem 1rem; margin: .6rem 0 .8rem; line-height: 1.5; overflow-x: auto; font-size: .95rem;
  white-space: pre; tab-size: 4;
}
pre.code .ln { display: inline-block; width: 2em; color: var(--muted); text-align: right; margin-right: 1em; user-select: none; font-size: .8em; }
pre.code .line { display: block; padding: 0 .4rem; margin: 0 -.4rem; border-radius: 4px; }
pre.code .line.cur { background: var(--sel); color: var(--sel-fg); }
pre.code .line.cur .kw, pre.code .line.cur .str, pre.code .line.cur .num, pre.code .line.cur .cmt, pre.code .line.cur .fn, pre.code .line.cur .ln { color: inherit; }
.kw { color: var(--kw); } .str { color: var(--str); } .num { color: var(--num); } .cmt { color: var(--cmt); font-style: italic; } .fn { color: var(--fn); }
pre.out, .out {
  font-family: var(--mono); font-size: .85rem;
  background: none; border-left: 3px solid var(--border); padding: .2rem .8rem; margin: .2rem 0 .6rem; white-space: pre-wrap; min-height: 1.4em;
}
.out .err { color: var(--bad); }
.out .label, .state .label { display: block; line-height: 1.6; }

/* generic visualization area */
.viz { display: grid; gap: 1rem; margin: .8rem 0; }
.viz.cols { grid-template-columns: minmax(0, 1.2fr) minmax(0, 1fr); align-items: start; }
.viz.cols3 { grid-template-columns: repeat(3, minmax(0, 1fr)); }
.viz.cols.loopvs { grid-template-columns: minmax(0, 2fr) minmax(0, 3fr); }
pre.code.wrap { white-space: pre-wrap; overflow-wrap: anywhere; }
.card { border: 1px solid var(--border); border-radius: 8px; padding: .8rem 1rem; }
.card h4 { margin: 0 0 .4rem; }

/* controls */
.controls { display: flex; flex-wrap: wrap; gap: .6rem 1.2rem; align-items: center; margin: .4rem 0; font-size: .9rem; }
.controls label { display: inline-flex; align-items: center; gap: .5rem; }
.controls label output, .controls .val { font-family: var(--mono); min-width: 2.5ch; color: var(--accent); }
input[type=range] { accent-color: var(--accent); width: 9rem; }
.controls label.off { color: var(--muted); }
.controls label.off output, .controls label.off input[type=range] { opacity: .35; }
.controls label.off output { color: var(--muted); }
input[type=checkbox] { accent-color: var(--accent); margin: 0; }
select, input[type=text] { font: inherit; font-size: .9rem; color: var(--fg); background: var(--bg); border: 1px solid var(--border); border-radius: 6px; padding: .2rem .5rem; }
input.mono { font-family: var(--mono); }
button.btn, .ops button {
  font: inherit; font-size: .85rem; color: var(--fg); background: var(--bg); border: 1px solid var(--border);
  border-radius: 6px; padding: .25rem .7rem; cursor: pointer;
}
button.btn:hover, .ops button:hover { border-color: var(--accent); color: var(--accent); }
button.btn:disabled { opacity: .4; cursor: default; }
.seg { display: inline-flex; border: 1px solid var(--border); border-radius: 6px; overflow: hidden; }
.seg button { font: inherit; font-size: .85rem; border: 0; background: none; color: var(--fg); padding: .25rem .7rem; cursor: pointer; }
.seg button + button { border-left: 1px solid var(--border); }
.seg button.on { background: var(--accent); color: var(--bg); }

/* cells: characters, list items, argv words */
.cells { display: flex; flex-wrap: wrap; gap: .3rem; align-items: flex-end; }
.cellcol { display: grid; grid-template-rows: auto auto auto; justify-items: center; gap: .15rem; }
.cell {
  font-family: var(--mono); font-size: 1.05rem;
  min-width: 2.4em; height: 2.4em; padding: 0 .5em; display: grid; place-items: center;
  border: 1px solid var(--border); border-radius: 6px; background: var(--code-bg); position: relative;
  transition: background .15s, transform .15s;
}
.cell.sel { background: var(--sel); color: var(--sel-fg); border-color: transparent; }
.cell.dim { opacity: .35; }
.cell.bad { border-color: var(--bad); color: var(--bad); border-style: dashed; }
.cell.new { outline: 2px solid var(--ok); outline-offset: 1px; }
.cell.ghost { border-style: dashed; background: none; color: var(--muted); }
.cell .ord { position: absolute; top: -.6em; right: -.4em; background: var(--accent); color: var(--bg); font-size: .6rem; border-radius: 999px; padding: 0 .4em; line-height: 1.5; }
.idx { font-family: var(--mono); font-size: .72rem; color: var(--muted); }
.idx.neg { color: var(--muted); opacity: .75; }
.idx.hot { color: var(--accent); font-weight: 600; opacity: 1; }
.bracket { font-family: var(--mono); font-size: 1.4rem; color: var(--muted); align-self: center; }

/* result line */
.result { font-family: var(--mono); font-size: 1rem; margin: .6rem 0 0; white-space: pre-wrap; }
.result .arrow { color: var(--muted); margin: 0 .5em; }
.result .err { color: var(--bad); }

/* tracer */
.tracer { display: grid; grid-template-columns: minmax(0, 1.15fr) minmax(0, 1fr); gap: 1rem; align-items: start; }
.tracer pre.code { margin: 0; }
.tracer .side { display: grid; gap: .7rem; }
.state { border: 1px solid var(--border); border-radius: 8px; padding: .6rem .8rem; }
.state .frame { margin-bottom: .5rem; }
.state .frame:last-child { margin-bottom: 0; }
.state .frame.fn { border-left: 3px solid var(--accent); padding-left: .6rem; margin-left: .2rem; }
.state .frame .fname { font-size: .72rem; color: var(--accent); font-family: var(--mono); }
.state .vars { display: flex; flex-wrap: wrap; gap: .35rem .6rem; margin-top: .2rem; }
.state .var { font-family: var(--mono); font-size: .9rem; background: var(--code-bg); border-radius: 6px; padding: .1em .5em; border: 1px solid transparent; }
.state .var.changed { border-color: var(--accent); background: var(--accent-bg); }
.state .var.ret { color: var(--ok); }
.state .empty { color: var(--muted); font-size: .85rem; }
.tracer .left { display: grid; gap: .6rem; align-content: start; }
.tracer .ctl { display: flex; align-items: center; gap: .4rem; font-size: .85rem; flex-wrap: wrap; }
.tracer .ctl .pos { color: var(--muted); font-family: var(--mono); margin-left: .4rem; }
.tracer .ctl .note { flex-basis: 100%; color: var(--fg); font-size: .9rem; min-height: 1.4em; }
.tracer .ctl .note:empty { display: none; }

/* names -> objects diagram */
.objdiag { position: relative; display: grid; grid-template-columns: auto 1fr; gap: 4.5rem; align-items: start; min-height: 6rem; }
.objdiag .names, .objdiag .objs { display: grid; gap: .6rem; }
.objdiag .name { font-family: var(--mono); border: 1px solid var(--border); border-radius: 6px; padding: .2rem .7rem; background: var(--bg); justify-self: start; }
.objdiag .obj { font-family: var(--mono); border: 1px solid var(--accent); border-radius: 8px; padding: .3rem .8rem; background: var(--accent-bg); justify-self: start; position: relative; }
.objdiag .obj .otype { position: absolute; top: -.75em; left: .6em; font-size: .6rem; background: var(--bg); color: var(--accent); padding: 0 .3em; font-family: inherit; }
.objdiag .obj.changed { outline: 2px solid var(--ok); }
.objdiag svg { position: absolute; inset: 0; width: 100%; height: 100%; pointer-events: none; overflow: visible; }
.objdiag svg path { fill: none; stroke: var(--muted); stroke-width: 1.5; }
.objdiag svg path.hot { stroke: var(--accent); stroke-width: 2; }

/* ops widget */
.ops { display: grid; gap: .3rem; align-content: start; }
.ops button { text-align: left; font-family: var(--mono); font-size: .9rem; white-space: pre-wrap; }
.ops button.on { border-color: var(--accent); background: var(--accent-bg); }
.ops button.done { color: var(--muted); }

/* dict */
.dict { display: grid; grid-template-columns: auto auto 1fr; gap: .35rem .8rem; align-items: center; font-family: var(--mono); font-size: .95rem; }
.dict .k, .dict .v { border: 1px solid var(--border); border-radius: 6px; padding: .15rem .6rem; background: var(--code-bg); justify-self: start; }
.dict .k { color: var(--str); }
.dict .ar { color: var(--muted); }
.dict .k.sel, .dict .v.sel { background: var(--sel); color: var(--sel-fg); border-color: transparent; }
.dict .k.new, .dict .v.new { outline: 2px solid var(--ok); }
.dict .k.gone, .dict .v.gone { opacity: .3; text-decoration: line-through; }

/* tooltips / hover reveals */
[data-tip] { position: relative; border-bottom: 1px dotted var(--accent); cursor: help; }
[data-tip]:hover::after {
  content: attr(data-tip); position: absolute; left: 0; top: 100%; z-index: 5; margin-top: .3rem;
  background: var(--fg); color: var(--bg); font: .8rem/1.4 var(--sans);
  padding: .35rem .6rem; border-radius: 6px; white-space: pre-line; width: max-content; max-width: 28rem;
}
.reveal { color: transparent; background: var(--code-bg); border-radius: 4px; transition: color .15s; cursor: pointer; }
.reveal:hover, .reveal.open { color: inherit; }

/* colour-coded parts (comprehensions, bindings) */
.g1 { background: var(--c1); border-radius: 4px; padding: 0 .15em; }
.g2 { background: var(--c2); border-radius: 4px; padding: 0 .15em; }
.g3 { background: var(--c3); border-radius: 4px; padding: 0 .15em; }
.g4 { background: var(--c4); border-radius: 4px; padding: 0 .15em; }
.grp.hot { outline: 2px solid var(--accent); }
.grp.cold { opacity: .35; }

/* flow (if/elif/else) */
.flow .line { display: flex; flex-wrap: wrap; align-items: center; gap: .4rem .8rem; }
.flow .badge { font: 600 .7rem/1.5 var(--sans); border-radius: 999px; padding: 0 .55em; }
.badge.t { background: var(--ok); color: var(--badge-fg); } .badge.f { background: var(--bad); color: var(--badge-fg); } .badge.skip { background: var(--border); color: var(--muted); }
.badge.type { background: var(--accent-bg); color: var(--accent); font: 600 .7rem/1.6 var(--sans); border-radius: 999px; padding: 0 .55em; vertical-align: middle; margin-left: .4em; }

/* dots for // and % */
.dots { display: grid; gap: .3rem; justify-content: start; }
.dots .row { display: flex; gap: .3rem; }
.dot { width: 1rem; height: 1rem; border-radius: 50%; background: var(--accent); opacity: .85; }
.dot.rem { background: var(--sel); border: 1px solid var(--num); }
.dots .row.rem { padding-top: .3rem; }

/* binder (arguments -> parameters) */
.binder .params { display: flex; flex-wrap: wrap; gap: .6rem; margin: .6rem 0; }
.binder .param { border: 1px solid var(--border); border-radius: 8px; padding: .3rem .7rem; font-family: var(--mono); font-size: .95rem; min-width: 6em; }
.binder .param .pn { font-size: .7rem; color: var(--muted); display: block; font-family: var(--sans); }
.binder .param.def { border-style: dashed; color: var(--muted); }
.binder .param.hot { border-color: var(--accent); background: var(--accent-bg); color: inherit; }
.binder .param.miss { border-color: var(--bad); color: var(--bad); }

/* terminal */
.term { background: #0f1115; color: #d8dee9; border-radius: 8px; padding: .8rem 1rem; font-family: var(--mono); font-size: .95rem; }
.term .prompt { color: #88c0d0; }
.term input { background: none; border: 0; color: inherit; font: inherit; width: 70%; outline: none; }

/* file box */
.file { border: 1px solid var(--border); border-radius: 8px; padding: .5rem .8rem; font-family: var(--mono); font-size: .9rem; white-space: pre; position: relative; }
.file .fname { position: absolute; top: -.75em; left: .6em; font-size: .65rem; background: var(--bg); color: var(--muted); padding: 0 .3em; font-family: var(--sans); }
.file .nl { color: var(--accent); opacity: .7; }
.file .ln { color: var(--muted); font-size: .8em; margin-right: 1em; }

/* home link in the toolbar */
.toolbar a.home { display: flex; align-items: center; color: var(--fg); padding: .2rem .45rem; border-radius: 999px; }
.toolbar a.home:hover { color: var(--accent); background: var(--accent-bg); }
.toolbar a.home svg { width: 1.05rem; height: 1.05rem; }

/* index page: list of setup + classes */
.toc { list-style: none; padding: 0; margin: 1.5rem 0 0; }
.toc li { border-bottom: 1px solid var(--border); }
.toc a, .toc .soon { display: grid; grid-template-columns: 12.5rem minmax(0, 1fr); gap: .15rem 1.5rem; padding: 1.3rem 0; color: inherit; text-decoration: none; }
.toc .when { grid-row: span 2; padding-top: .45rem; }
.toc .title { font-family: var(--mono); font-size: 1.35rem; font-weight: 500; letter-spacing: -0.018em; }
.toc .what { color: var(--muted); }
.toc a:hover .title { color: var(--accent); }
.toc .soon { opacity: .4; cursor: default; }

/* reading pages (setup): narrower column, numbered steps, notes, tables, folds */
main.narrow { max-width: 46rem; }
pre.code code { background: none; padding: 0; font-size: inherit; }
ol.steps { counter-reset: st; list-style: none; padding-left: 0; }
ol.steps > li { counter-increment: st; position: relative; padding-left: 2.6rem; margin: 1.4rem 0; }
ol.steps > li::before {
  content: counter(st); position: absolute; left: 0; top: .05rem; width: 1.8rem; height: 1.8rem; border-radius: 50%;
  border: 1.5px solid var(--accent); color: var(--accent); display: grid; place-items: center; font: 500 .85rem var(--mono);
}
ol.steps > li > strong { display: block; margin-bottom: .2rem; }
.note { background: var(--accent-bg); border-left: 3px solid var(--accent); padding: .5rem .9rem; margin: 1rem 0; border-radius: 0 6px 6px 0; }
.note p { margin: .3rem 0; }
table.plain { border-collapse: collapse; width: 100%; margin: .8rem 0 1.2rem; font-size: .95em; }
table.plain th, table.plain td { text-align: left; padding: .45rem .6rem; border-bottom: 1px solid var(--border); vertical-align: top; }
table.plain th { font-family: var(--mono); font-size: .66rem; letter-spacing: .14em; text-transform: uppercase; color: var(--muted); font-weight: 500; }
details { margin: .6rem 0; }
summary { cursor: pointer; font-weight: 600; }
footer.doc { margin-top: 2rem; color: var(--muted); font-size: .9em; }

@media (max-width: 900px) {
  main { padding: 1rem 16px 4rem; }
  .viz.cols, .viz.cols3, .tracer { grid-template-columns: 1fr; }
  html { font-size: 17px; }
  .toc a, .toc .soon { grid-template-columns: 1fr; }
  .toc .when { grid-row: auto; padding-top: 0; }
}