/* ============================================================================
   book.css — the web book, layered on org-css.css
   ----------------------------------------------------------------------------
   org-css.css (vendored from sarangop1728.github.io) supplies the tokens,
   type, links and code blocks, so the notes read like the rest of the site.
   This file adds only what a book needs: the contents sidebar, chapter
   headings, numbered statements set the way amsthm sets them, proofs,
   chapter navigation and the per-chapter reference list.
   ============================================================================ */


/* === 1. Tokens ============================================================ */

:root {
  --ec-sidebar-width: 17.5rem;
  --ec-measure: 44rem;               /* about 70 characters of Charter */
  --ec-gutter: clamp(1rem, 4vw, 3rem);

  /* A faint wash of the site's link blue, for statements a reader scans for. */
  --ec-statement-ground: #eef4f8;
  --ec-statement-edge: #d6e4ee;
  --ec-sidebar-ground: #f6f8f9;
  --ec-current-ground: #e3eef6;
  --ec-number: #5d7185;

  /* Section status labels (lib/ec-status.el).  The PDF's ecstatus* colours
     in lib/preamble-overrides.tex are the light values; change both together. */
  --ec-status-draft: #8a6100;
  --ec-status-todo: #b3401e;
}

/* org-css.css switches to dark only through the media query.  The viewer's
   explicit theme choice has to win in both directions, so the dark tokens
   are restated for [data-theme="dark"] and the light ones for
   [data-theme="light"] on a dark system. */
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --ec-statement-ground: #18212b;
    --ec-statement-edge: #243241;
    --ec-sidebar-ground: #171a20;
    --ec-current-ground: #1f2d3a;
    --ec-number: #8fa3b6;
    --ec-status-draft: #d9a93a;
    --ec-status-todo: #f08a6c;
  }
  :root[data-theme="light"] {
    --ec-status-draft: #8a6100;
    --ec-status-todo: #b3401e;
    --bg-page: #ffffff; --bg-card: #f8f9f9; --bg-code: #f2f2f2; --bg-toc: #ffffff;
    --bg-th: #111318; --text: #34495e; --text-muted: #6b7c8f; --heading: #111318;
    --text-th: #ffffff; --rule: #dddddd; --border: #d0d7de; --link: #2a8ac0;
    --syn-keyword: #a626a4; --syn-string: #50a14f; --syn-comment: #8a9199;
    --syn-function: #4078f2; --syn-variable: #986801; --syn-constant: #0184bc;
    --syn-type: #c18401; --syn-builtin: #b76b01;
  }
}

:root[data-theme="dark"] {
  --bg-page: #14171c; --bg-card: #1b1f26; --bg-code: #12151b; --bg-toc: #22272f;
  --bg-th: #2d333b; --text: #c9d1d9; --text-muted: #8b949e; --heading: #e8edf3;
  --text-th: #e8edf3; --rule: #30363d; --border: #30363d; --link: #6bb8e8;
  --syn-keyword: #c678dd; --syn-string: #98c379; --syn-comment: #7f8c98;
  --syn-function: #61afef; --syn-variable: #e5c07b; --syn-constant: #56b6c2;
  --syn-type: #e5c07b; --syn-builtin: #d19a66;
  --ec-statement-ground: #18212b;
  --ec-statement-edge: #243241;
  --ec-sidebar-ground: #171a20;
  --ec-current-ground: #1f2d3a;
  --ec-number: #8fa3b6;
  --ec-status-draft: #d9a93a;
  --ec-status-todo: #f08a6c;
}


/* === 2. Page layout ======================================================= */
/* Sidebar on the left, one reading column beside it.  #preamble holds the
   sidebar and the top pager; `display: contents' lets each take its own
   place in the grid. */

body {
  background: var(--bg-page);
  display: grid;
  grid-template-columns: var(--ec-sidebar-width) minmax(0, 1fr);
  grid-template-areas:
    "sidebar pager-top"
    "sidebar content"
    "sidebar pager-bottom";
  grid-template-rows: auto 1fr auto;
  min-height: 100vh;
}

#preamble, #postamble { display: contents; }

.ec-sidebar       { grid-area: sidebar; }
.ec-pager-top     { grid-area: pager-top; }
#content          { grid-area: content; }
.ec-pager-bottom  { grid-area: pager-bottom; }

/* The site's card look suits a single page; a book reads better on the page. */
#content {
  background: none;
  border: 0;
  border-radius: 0;
  margin: 0;
  width: 100%;
  max-width: calc(var(--ec-measure) + 2 * var(--ec-gutter));
  padding: 1rem var(--ec-gutter) 3rem;
  justify-self: center;
}


/* === 3. Sidebar =========================================================== */

.ec-sidebar {
  position: sticky;
  top: 0;
  align-self: start;
  height: 100vh;
  overflow-y: auto;
  overscroll-behavior: contain;
  background: var(--ec-sidebar-ground);
  border-right: 1px solid var(--rule);
  padding: 1.5rem 1rem 2rem;
  font-family: var(--font-sans);
  font-size: 0.875rem;
  line-height: 1.35;
}

.ec-book-title {
  display: block;
  color: var(--heading);
  font-weight: 650;
  font-size: 1rem;
  line-height: 1.25;
  text-wrap: balance;
}
.ec-book-title:hover { text-decoration: none; color: var(--link); }

.ec-book-subtitle {
  margin: 0.25rem 0 1.25rem;
  color: var(--text-muted);
  font-size: 0.8125rem;
}

.ec-toc, .ec-toc-sections {
  list-style: none;
  margin: 0;
  padding: 0;
}

.ec-toc a {
  display: grid;
  grid-template-columns: 2.4em minmax(0, 1fr);
  gap: 0.25em;
  padding: 0.35rem 0.5rem;
  border-radius: 6px;
  color: var(--text);
}
.ec-toc a:hover { background: var(--ec-current-ground); text-decoration: none; }

.ec-toc-num {
  color: var(--ec-number);
  font-variant-numeric: tabular-nums;
}

.ec-toc-chapter.is-current > a {
  background: var(--ec-current-ground);
  color: var(--heading);
  font-weight: 600;
}

.ec-toc-sections { margin: 0.2rem 0 0.5rem; }
.ec-toc-sections a {
  grid-template-columns: 3.4em minmax(0, 1fr);
  font-size: 0.8125rem;
  padding-block: 0.25rem;
}
.ec-toc-sections .ec-toc-level-1 a { padding-left: 1.1rem; }
.ec-toc-sections .ec-toc-level-2 a { padding-left: 2rem; grid-template-columns: 4.2em minmax(0, 1fr); }
.ec-toc-sections a.is-active { color: var(--link); }
.ec-toc-sections a.is-active .ec-toc-num { color: var(--link); }

/* The glossary, after the chapters. */
.ec-toc-glossary {
  display: block;
  margin-top: 0.75rem;
  padding: 0.35rem 0.5rem;
  border-radius: 6px;
  color: var(--text);
}
.ec-toc-glossary:hover { background: var(--ec-current-ground); text-decoration: none; }
.ec-toc-glossary.is-current {
  background: var(--ec-current-ground);
  color: var(--heading);
  font-weight: 600;
}

.ec-menu { display: none; }


/* === 4. Chapter title and sections ======================================== */

#content .title {
  font-size: clamp(1.75rem, 4vw, 2.5rem);
  text-wrap: balance;
  margin: 1.5rem 0 2rem;
}

.ec-chapter-label {
  display: block;
  margin-bottom: 0.4rem;
  font-size: 0.8125rem;
  font-weight: 600;
  letter-spacing: 0.14em;
  text-transform: uppercase;
  color: var(--ec-number);
}

#content h2, #content h3, #content h4 { text-wrap: balance; scroll-margin-top: 1rem; }

.section-number {
  color: var(--ec-number);
  font-variant-numeric: tabular-nums;
  margin-right: 0.6em;
  font-weight: 500;
}

#content p, #content li { hyphens: auto; }


/* === 5. Numbered statements =============================================== */
/* Set as amsthm sets them in the PDF.  Theorem, lemma, proposition,
   corollary and conjecture are the statements a reader hunts for, so they
   get a box, and their text is italic (the `plain' style).  Every other
   numbered statement stays upright, between two lines from its heading to
   its last line.  lib/preamble-overrides.tex draws the same boxes and lines
   in the PDF; change the two together. */

.ec-thm { margin: 1.4em 0; scroll-margin-top: 1rem; }
.ec-thm > p:first-child { margin-top: 0; }
.ec-thm > :last-child { margin-bottom: 0; }

.ec-thm-head { font-style: normal; }
.ec-thm-name {
  font-variant: small-caps;
  letter-spacing: 0.02em;
  color: var(--heading);
  font-weight: 600;
  font-variant-numeric: tabular-nums;
}
.ec-thm-title { color: var(--heading); }

.ec-theorem, .ec-lemma, .ec-proposition, .ec-corollary, .ec-conjecture {
  background: var(--ec-statement-ground);
  border: 1px solid var(--ec-statement-edge);
  border-radius: 4px;
  padding: 0.85em 1.1em;
  font-style: italic;
}

.ec-definition, .ec-example, .ec-remark, .ec-remarks, .ec-question,
.ec-answer, .ec-fact, .ec-algorithm, .ec-warning, .ec-situation {
  border-left: 3px solid var(--ec-statement-edge);
  border-right: 3px solid var(--ec-statement-edge);
  padding: 0 1.1em;
}

/* #+begin_sources, under the chapter title: the books the chapter draws on.
   Unnumbered; the PDF's `sources' environment in preamble-overrides.tex. */
.sources, .ec-wip {
  border-left: 3px solid var(--ec-statement-edge);
  padding-left: 1.1em;
  margin: 0 0 2em;
  font-size: 0.9em;
  color: var(--text-muted);
}
.sources > :first-child, .ec-wip > :first-child { margin-top: 0; }
.sources > :last-child, .ec-wip > :last-child { margin-bottom: 0; }
.sources > p:first-child::before { content: "Sources. "; font-style: italic; }

/* #+begin_wip in book.org, on the index page: the PDF's `wip' environment,
   set after its contents.  The legend and the date come from lib/ec-status.el. */
.ec-wip p { margin: 0.45em 0; }
.ec-wip > p:first-child::before { content: "About these notes. "; font-style: italic; }


/* Section status (lib/ec-status.el).  A section marked DRAFT or TODO shows
   its label and the date it last changed beside its heading: in the left
   margin when there is room, as \ecstatus does in the PDF, and otherwise on
   a line above the heading.  The contents repeat the label, and each
   chapter's progress, as the PDF's contents do. */
.ec-status-label {
  font-family: var(--font-sans);
  font-size: 0.6875rem;
  font-weight: 700;
  font-style: normal;
  letter-spacing: 0.06em;
  text-transform: uppercase;
  white-space: nowrap;
}
.ec-status-draft { color: var(--ec-status-draft); }
.ec-status-todo { color: var(--ec-status-todo); }
.ec-status-progress {
  font-family: var(--font-sans);
  font-size: 0.75rem;
  font-weight: 400;
  color: var(--text-muted);
  white-space: nowrap;
}

#content .ec-status {
  display: flex;
  align-items: baseline;
  gap: 0.6em;
  margin-bottom: 0.3rem;
  line-height: 1.2;
}
.ec-status time {
  font-family: var(--font-sans);
  font-size: 0.75rem;
  font-weight: 400;
  color: var(--text-muted);
  white-space: nowrap;
}
@media (min-width: 76rem) {
  #content h2 { position: relative; }
  #content h2 > .ec-status {
    position: absolute;
    right: 100%;
    top: 0.35em;
    margin: 0 1.25rem 0 0;
    flex-direction: column;
    align-items: flex-end;
    gap: 0.15rem;
  }
}

.ec-toc-status { display: block; margin-top: 0.1rem; line-height: 1.2; }

/* Figures and inline diagrams: TikZ compiled to SVG (lib/ec-export.el), at
   the PDF's size.  The pictures are drawn for white paper, in black with
   colour, so they sit on a white card in both themes. */
.ec-figure { margin: 1.4em 0; text-align: center; scroll-margin-top: 1rem; }
.ec-diagram { margin: 1em 0; text-align: center; }
/* --ec-w is the picture's width in em, from its size in the PDF against the
   book's 10pt text (lib/ec-export.el), so a picture keeps its size relative
   to the text; the calc adds this rule's padding and border.  Without
   --ec-w the width is invalid and falls back to the picture's own. */
img.ec-tikz {
  display: inline-block;
  box-sizing: border-box;
  width: calc(var(--ec-w) + 1.2em + 2px);
  max-width: 100%;
  height: auto;
  padding: 0.6em;
  background: #ffffff;
  border: 1px solid var(--ec-statement-edge);
  border-radius: 4px;
}
/* Pictures side by side in one figure, spaced like the PDF's \hspace{3em}.
   They shrink together to fit the column, which is narrower than the PDF's
   text, and stack one above the other on a phone, where the gap drops out. */
.ec-figure:has(> img.ec-tikz + img.ec-tikz) {
  display: flex;
  flex-wrap: wrap;
  justify-content: center;
  align-items: center;     /* on their centres, as the PDF's baseline= */
  gap: 0.6em 3em;
}
.ec-figure:has(> img.ec-tikz + img.ec-tikz) > img.ec-tikz { max-width: calc(50% - 1.5em); }
.ec-figure:has(> img.ec-tikz + img.ec-tikz) > figcaption { flex-basis: 100%; }
@media (max-width: 40rem) {
  .ec-figure:has(> img.ec-tikz + img.ec-tikz) > img.ec-tikz { max-width: 100%; }
}
.ec-figure figcaption {
  margin-top: 0.6em;
  text-align: left;
  font-size: 0.9em;
  color: var(--text-muted);
}

/* The target of a link flashes its edge, so the eye lands on it. */
.ec-thm:target, .ec-figure:target { outline: 2px solid var(--link); outline-offset: 3px; }

/* Proofs are folded, so the statements carry the page.  A <details> needs no
   script: with book.js missing the folds still open and close.  Closed, a
   proof is one line; open, its summary floats left and the body flows around
   it, which is the PDF's run-in "Proof.".  A proof that only points at the
   literature names its sources while folded (lib/ec-export.el), and drops
   them once it is open, where the body says the same thing at length. */
details.ec-proof { margin: -0.4em 0 1.4em; scroll-margin-top: 1rem; }
.ec-proof > summary { cursor: pointer; list-style: none; }
.ec-proof > summary::-webkit-details-marker { display: none; }
.ec-proof-head { font-style: italic; }
.ec-proof-cites { font-style: normal; font-size: 0.9em; color: var(--text-muted); }
.ec-proof[open] .ec-proof-cites { display: none; }
.ec-proof > summary:hover .ec-proof-head { color: var(--link); }
.ec-proof > summary:focus-visible { outline: 2px solid var(--link); outline-offset: 2px; }

/* The fold's affordance, in place of the browser's triangle.  It shows only
   while the proof is closed: in an open proof it would sit inside the run-in,
   between "Proof." and the first word.  The italic head stays the handle --
   it tints on hover and carries the pointer cursor. */
.ec-proof:not([open]) > summary::after {
  content: "\25B8";
  margin-left: 0.35em;
  font-style: normal;
  color: var(--text-muted);
}

/* The run-in only when the body opens with a paragraph: a proof that opens
   with a list or a displayed equation keeps its head on a line of its own,
   as it did before the fold. */
.ec-proof[open]:has(> summary + p) > summary { float: left; margin-right: 0.35em; }

.ec-proof > :last-child::after {
  content: "\25A1";                  /* the PDF's end-of-proof square */
  float: right;
  margin-left: 1em;
  color: var(--text-muted);
}

/* \cdef: a defined term, the web's \defi (blue sans serif in the PDF).
   data-gls holds its glossary key. */
.ec-cdef {
  font-style: normal;
  font-family: var(--font-sans);
  font-size: 0.95em;
  color: var(--link);
  scroll-margin-top: 4rem;
}
:target.ec-cdef { outline: 2px solid var(--link); outline-offset: 2px; border-radius: 2px; }

/* The glossary page: term, description, then where it is defined. */
.ec-gls-term { font-weight: 600; color: var(--heading); }
.ec-gls-where {
  margin-left: 0.4em;
  font-family: var(--font-sans);
  font-size: 0.8125rem;
  white-space: nowrap;
}

/* Displayed equations scroll on their own on a narrow screen. */
mjx-container[display="true"] {
  overflow-x: auto;
  overflow-y: hidden;
  max-width: 100%;
}


/* === 6. Citations and references ========================================== */

.ec-cite, .ec-eqref { white-space: nowrap; }

.ec-references h2 { font-size: 1.25rem; }

.ec-bibliography {
  display: grid;
  grid-template-columns: max-content minmax(0, 1fr);
  column-gap: 1em;
  row-gap: 0.6em;
  margin: 1em 0 0;
  font-size: 0.9375rem;
}
.ec-bibliography dt {
  font-family: var(--font-sans);
  font-size: 0.875rem;
  color: var(--ec-number);
  font-variant-numeric: tabular-nums;
  padding-top: 0.1em;
}
.ec-bibliography dd { margin: 0; overflow-wrap: anywhere; }
.ec-bibliography dt:target, .ec-bibliography dt:target + dd { color: var(--heading); }
.ec-bibliography dt:target { outline: 2px solid var(--link); outline-offset: 2px; border-radius: 2px; }


/* === 7. Chapter navigation ================================================ */

.ec-pager {
  display: grid;
  grid-template-columns: 1fr 1fr;
  gap: 1rem;
  width: 100%;
  max-width: calc(var(--ec-measure) + 2 * var(--ec-gutter));
  justify-self: center;
  padding: 0.9rem var(--ec-gutter);
  font-family: var(--font-sans);
  font-size: 0.875rem;
}
.ec-pager-top { border-bottom: 1px solid var(--rule); }
.ec-pager-bottom { border-top: 1px solid var(--rule); padding-bottom: 2.5rem; }

.ec-pager a { display: grid; gap: 0.1rem; color: var(--text); }
.ec-pager a:hover { text-decoration: none; }
.ec-pager a:hover .ec-pager-title { color: var(--link); }
.ec-pager-next { text-align: right; grid-column: 2; }
.ec-pager-prev { grid-column: 1; }
.ec-pager-label {
  font-size: 0.75rem;
  letter-spacing: 0.08em;
  text-transform: uppercase;
  color: var(--text-muted);
}
.ec-pager-title { color: var(--heading); text-wrap: balance; }
.ec-pager-top .ec-pager-label { display: none; }
.ec-pager-top { color: var(--text-muted); }


/* === 8. Index page ======================================================== */

.ec-index .subtitle { font-family: var(--font-sans); margin: -1.25rem 0 0.25rem; }
.ec-index-author { color: var(--text-muted); margin-top: 0; }

.ec-index-chapters { list-style: none; padding: 0; margin: 1rem 0; }
.ec-index-chapters li {
  display: flex;
  align-items: baseline;
  gap: 0.75rem;
  padding: 0.45rem 0;
  border-bottom: 1px solid var(--rule);
}
.ec-index-chapters a {
  display: grid;
  grid-template-columns: 2.2em minmax(0, 1fr);
  flex: 1;
  color: var(--heading);
}


/* === 9. Narrow screens ==================================================== */

@media (max-width: 60rem) {
  body {
    grid-template-columns: minmax(0, 1fr);
    grid-template-areas: "pager-top" "content" "pager-bottom";
  }

  .ec-menu {
    display: block;
    position: fixed;
    right: 1rem;
    bottom: 1rem;
    z-index: 30;
    font: 600 0.875rem/1 var(--font-sans);
    color: var(--bg-page);
    background: var(--heading);
    border: 0;
    border-radius: 999px;
    padding: 0.75rem 1.1rem;
    box-shadow: 0 2px 10px var(--shadow-strong);
    cursor: pointer;
  }
  .ec-menu:focus-visible { outline: 2px solid var(--link); outline-offset: 3px; }

  .ec-sidebar {
    position: fixed;
    inset: 0 auto 0 0;
    z-index: 20;
    width: min(var(--ec-sidebar-width), 85vw);
    transform: translateX(-100%);
    visibility: hidden;
    transition: transform 0.2s ease, visibility 0.2s;
    box-shadow: 4px 0 24px var(--shadow);
  }
  .ec-nav-open .ec-sidebar { transform: none; visibility: visible; }
}

@media (prefers-reduced-motion: reduce) {
  .ec-sidebar { transition: none; }
}

@media print {
  .ec-sidebar, .ec-pager, .ec-menu { display: none; }
  body { display: block; }
}