/* ===========================================================================
   style.css — whole site.

   Sections:
     1. tokens
     2. base            — reset, body type, links
     3. header          — masthead (notes) and page-head (home)
     4. home page
     5. notes page      — rail, note bodies, sidenotes, math
     6. narrow screens
     7. print

   The measure lives on page wrappers, not on body: the notes page needs a
   frame wider than its text column (rail + text + sidenote margin), so a
   max-width on body would clamp it.
=========================================================================== */


/* --- 1. tokens ---------------------------------------------------------- */

@font-face {
  font-family: "Lastik";
  src: url("../fonts/LastikFreeFont-Free.woff2") format("woff2");
  font-weight: normal;
  font-style: normal;
  font-display: swap;
}

:root {
  --frame-home: 42rem;    /* ~75 characters in Charter */
  --frame-notes: 78rem;   /* rail + text + sidenote margin, plus air */
  --text: 46rem;          /* measure of the notes reading column */
  --side: 18rem;          /* width of a sidenote */
  --side-gap: 3.5rem;     /* space between text and sidenote */
  --rail: 12.5rem;        /* width of the notes list on the left */
  --pad: 1.5rem;          /* gutter either side of the frame */

  --display: "Lastik", Georgia, serif;
  --body: Charter, "Iowan Old Style", Georgia, serif;
  --mono: ui-monospace, "SF Mono", Menlo, Consolas, monospace;

  --ink: #1a1a1a;
  --ink-muted: #555;
  --rule: #d8d8d8;
  --title: #4684bf;       /* accent: note titles, sidenote numbers */
  --link-hover: #0000cc;
}


/* --- 2. base ------------------------------------------------------------ */

*,
*::before,
*::after {
  box-sizing: border-box;
}

html {
  color-scheme: light;
  scroll-behavior: smooth;
  -webkit-text-size-adjust: 100%;
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
}

body {
  margin: 4rem 0 5rem;
  font-family: var(--body);
  font-size: 1rem;
  line-height: 1.5;
  color: var(--ink);
  background: #fff;
}

a {
  color: var(--ink);
  text-decoration-thickness: 1px;
  text-underline-offset: 2px;
}

a:hover {
  color: var(--link-hover);
}

:focus-visible {
  outline: 2px solid var(--link-hover);
  outline-offset: 2px;
}

.skip-link {
  position: absolute;
  left: -9999px;
}

.skip-link:focus {
  left: 1rem;
  top: 1rem;
  background: #fff;
  padding: 0.4rem 0.6rem;
  z-index: 10;
}


/* --- 3. header ----------------------------------------------------------

   Two variants of the same idea: name left, nav right, sharing a baseline.
   .page-head is the home page, where the name is the page title;
   .masthead is every other page, where it shrinks to a link back home.
------------------------------------------------------------------------- */

.page-head,
.masthead {
  display: flex;
  flex-wrap: wrap;
  align-items: baseline;
  justify-content: space-between;
  gap: 0.75rem 2rem;
  margin: 0 auto 2.5rem;
  padding: 0 var(--pad);
}

.page-head {
  max-width: var(--frame-home);
}

.masthead {
  max-width: var(--frame-notes);
}

.page-head h1 {
  font-family: var(--display);
  font-size: 2.25rem;
  font-weight: normal;
  line-height: 1.15;
  margin: 0;
}

.masthead-name {
  font-family: var(--display);
  font-size: 1.15rem;
  color: var(--ink);
  text-decoration: none;
}

/* a row with real space between links — no pipe characters, which stack into
   a vertical stripe as soon as the nav wraps or turns into a column */
.site-nav {
  display: flex;
  gap: 1.1rem;
  font-size: 0.95rem;
}


/* --- 4. home page ------------------------------------------------------- */

.home {
  max-width: var(--frame-home);
  margin: 0 auto;
  padding: 0 var(--pad);
}

.home p {
  margin: 0 0 1.1rem;
}

.home ul {
  margin: 1.5rem 0 0;
  padding-left: 1.2rem;
}

.home li {
  margin-bottom: 0.35rem;
}


/* --- 5. notes page ------------------------------------------------------

   Three bands, left to right: a sticky list of notes, the text column, and
   the margin the sidenotes live in.
------------------------------------------------------------------------- */

.layout {
  display: grid;
  grid-template-columns: var(--rail) minmax(0, 1fr);
  gap: 0.5rem;
  max-width: var(--frame-notes);
  margin: 0 auto;
  padding: 0 var(--pad);
}

.note-index {
  min-width: 0;
}

.note-index h1 {
  font-family: var(--display);
  font-size: 1.5rem;
  font-weight: normal;
  margin: 0 0 1.5rem;
}

/* the notes list (left rail) */
.toc {
  position: sticky;
  top: 1.25rem;
  align-self: start;
  max-height: calc(100vh - 2.5rem);
  overflow-y: auto;
  overscroll-behavior: contain;
  font-size: 0.85rem;
  line-height: 1.35;
}

.toc-heading {
  margin: 0 0 0.6rem;
  font-style: italic;
  color: var(--ink-muted);
}

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

.toc-list > li {
  padding: 0.3rem 0 0.3rem 0.6rem;
  border-left: 1px solid var(--rule);
}

.toc-list a {
  color: var(--ink);
  text-decoration: none;
}

.toc-list a:hover {
  color: var(--link-hover);
  text-decoration: underline;
}

.toc-date {
  display: block;
  color: #8a8a8a;
  font-size: 0.75rem;
  font-style: italic;
}

/* the current note gets the accent, and only it shows its subheadings */
.toc-list > li.is-current {
  border-left: 2px solid var(--title);
  padding-left: calc(0.6rem - 1px);
}

.toc-list > li.is-current > a {
  color: var(--title);
}

.toc-sub {
  display: none;
  margin: 0.35rem 0 0.1rem 0.15rem;
  border-left: 1px solid var(--rule);
}

.toc-list > li.is-current > .toc-sub {
  display: block;
}

.toc-sub li {
  padding: 0.15rem 0 0.15rem 0.55rem;
}

.toc-sub a {
  color: var(--ink-muted);
}

.toc-toggle {
  display: none;
  font: inherit;
  font-size: 0.9rem;
  background: none;
  border: 0;
  border-bottom: 1px solid var(--rule);
  width: 100%;
  text-align: left;
  padding: 0 0 0.35rem;
  margin-bottom: 0.6rem;
  color: var(--ink);
  cursor: pointer;
}

.toc-toggle::after {
  content: " \25be";
  color: var(--ink-muted);
}

.toc-toggle[aria-expanded="false"]::after {
  content: " \25b8";
}

/* a note */
.note-block {
  max-width: var(--text);
  scroll-margin-top: 1.25rem;
}

.note-inline-title {
  font-family: var(--display);
  color: var(--title);
  font-size: 1.35rem;
  font-weight: normal;
  text-decoration: underline;
  text-underline-offset: 3px;
  margin: 0 0 0.25rem;
  line-height: 1.2;
}

.note-inline-date {
  font-style: italic;
  margin: 0 0 0.85rem;
  font-size: 0.95rem;
}

.note-source {
  margin: -0.6rem 0 0.85rem;
  font-size: 0.95rem;
  font-weight: bold;
}

.note-continues {
  margin: -0.5rem 0 0.85rem;
  font-size: 0.92rem;
  font-style: italic;
  color: #444;
}

.note-permalink {
  margin-left: 0.45rem;
  font-weight: normal;
  color: #bbb;
  text-decoration: none;
  opacity: 0.55;
  transition: opacity 0.12s, color 0.12s;
}

.note-permalink svg {
  vertical-align: middle;
  position: relative;
  top: -0.12em;
}

.note-block:hover .note-permalink,
.note-permalink:focus-visible {
  opacity: 1;
}

.note-permalink:hover {
  color: var(--link-hover);
}

.note-permalink.copied {
  color: #2e7d32;
  opacity: 1;
}

.note-permalink.copied::after {
  content: " link copied";
  font-size: 0.75rem;
  font-style: italic;
}

.note-sep {
  border: 0;
  border-top: 1px solid var(--ink);
  max-width: var(--text);
  margin: 1.75rem 0;
}

/* note body */
.note-body {
  counter-reset: sidenote;
}

.note-body p,
.note-body ul,
.note-body ol {
  margin: 0 0 0.9rem;
}

.note-body ul,
.note-body ol {
  padding-left: 1.2rem;
}

.note-body li {
  margin-bottom: 0.35rem;
}

.note-body li:last-child,
.note-body > :last-child {
  margin-bottom: 0;
}

.note-body h3,
.note-body h4 {
  font-size: 1rem;
  margin: 1.4rem 0 0.5rem;
  scroll-margin-top: 1.25rem;
}

.note-body h4 {
  font-style: italic;
  font-weight: normal;
}

.note-body blockquote {
  margin: 0 0 0.9rem;
  padding-left: 1rem;
  border-left: 2px solid var(--rule);
  color: #333;
}

.note-body code {
  font-family: var(--mono);
  font-size: 0.9em;
}

.note-body pre {
  background: #f6f6f6;
  border: 1px solid #e2e2e2;
  border-radius: 4px;
  padding: 0.75rem 0.9rem;
  overflow-x: auto;
  margin: 0 0 0.9rem;
}

.note-body pre code {
  font-size: 0.85rem;
  line-height: 1.4;
}

/* tables scroll inside their own box instead of widening the column */
.note-body .table-scroll {
  overflow-x: auto;
  max-width: 100%;
  margin: 0 0 1rem;
}

.note-body table {
  border-collapse: collapse;
  width: 100%;
  min-width: max-content;
  font-size: 0.92rem;
}

.note-body th,
.note-body td {
  border: 1px solid #ccc;
  padding: 0.3rem 0.6rem;
}

.note-body th {
  background: #f3f3f3;
  text-align: left;
}

.note-body figure {
  margin: 1.25rem 0;
}

.note-body img,
.note-body svg {
  max-width: 100%;
  height: auto;
}

.note-body figcaption {
  font-size: 0.92rem;
  font-style: italic;
  color: #333;
  margin-top: 0.5rem;
}

.note-body .note-diagram {
  margin: 1.5rem 0;
  text-align: center;
}

.note-body .note-callout {
  border: 1px solid #ccc;
  padding: 0.75rem 1rem;
  margin: 1.25rem 0;
  text-align: center;
  line-height: 1.5;
}

.note-body .note-centered {
  text-align: center;
}

.note-body .note-centered p {
  margin-bottom: 0.4rem;
}

/* `::: wide` escapes the measure — for a big table, plot, or diagram */
.note-body .note-wide {
  width: calc(var(--text) + var(--side-gap) + var(--side));
  max-width: calc(100vw - 3rem);
  margin: 1.5rem 0;
}

/* math */
eq {
  overflow-wrap: anywhere;
}

/* display math wider than the column scrolls sideways. Centering uses flex
   `safe center` rather than text-align: a centered overflow spills equally
   both ways and the left half becomes unreachable. */
.note-body section {
  display: flex;
  justify-content: safe center;
  margin: 1rem 0;
  max-width: 100%;
  overflow-x: auto;
  overflow-y: hidden;
  padding-bottom: 0.15rem;
}

.note-body section > eqn {
  display: block;
  min-width: 0;
}

.note-body .katex-display {
  margin: 0;
  overflow: visible;
}

/* sidenotes */
.sidenote-toggle {
  position: absolute;
  width: 1px;
  height: 1px;
  opacity: 0;
}

.sidenote-number,
.margin-symbol {
  cursor: pointer;
  counter-increment: sidenote;
}

.sidenote-number::after {
  content: counter(sidenote);
  font-size: 0.7rem;
  vertical-align: super;
  line-height: 0;
  color: var(--title);
  padding-left: 0.06em;
}

.margin-symbol {
  display: none;
  color: var(--title);
}

.sidenote {
  float: right;
  clear: right;
  width: var(--side);
  margin-right: calc(-1 * (var(--side) + var(--side-gap)));
  margin-bottom: 0.8rem;
  font-size: 0.82rem;
  line-height: 1.4;
  color: #333;
  text-align: left;
  position: relative;
}

.sidenote::before {
  content: counter(sidenote) " ";
  font-size: 0.7rem;
  vertical-align: super;
  line-height: 0;
  color: var(--title);
}

.sidenote.marginnote::before {
  content: none;
}

.sidenote eq {
  font-size: 0.95em;
}

.sidenote-toggle:focus-visible + .sidenote-number,
.sidenote-toggle:focus-visible + .margin-symbol {
  outline: 2px solid var(--link-hover);
  outline-offset: 2px;
}


/* --- 6. narrow screens -------------------------------------------------- */

/* no room for the rail: the list moves above the notes and collapses */
@media (max-width: 1120px) {
  .layout {
    grid-template-columns: minmax(0, 1fr);
    gap: 1.5rem;
    max-width: calc(var(--text) + var(--side-gap) + var(--side) + 3rem);
  }

  .toc {
    position: static;
    max-height: none;
    overflow: visible;
  }

  .toc-heading {
    display: none;
  }

  .toc-toggle {
    display: block;
  }

  .toc-list {
    columns: 2;
    column-gap: 1.5rem;
  }

  .toc-list > li {
    break-inside: avoid;
  }

  .toc-sub {
    display: none !important;
  }
}

/* no room for the margin: sidenotes fold into the text, opened by tapping
   their number */
@media (max-width: 900px) {
  .layout {
    max-width: calc(var(--text) + 3rem);
  }

  .margin-symbol {
    display: inline;
  }

  .sidenote {
    display: none;
    float: none;
    width: 100%;
    max-width: 100%;
    margin: 0.7rem 0 1rem;
    padding: 0.6rem 0.8rem;
    border-left: 2px solid var(--rule);
    background: #fafafa;
  }

  .sidenote-toggle:checked + .sidenote-number + .sidenote,
  .sidenote-toggle:checked + .margin-symbol + .sidenote {
    display: block;
  }

  .note-body .note-wide {
    width: 100%;
  }

  .toc-list {
    columns: 1;
  }
}

@media (max-width: 480px) {
  :root { --pad: 1rem; }

  body { margin-top: 2rem; }

  .page-head h1 { font-size: 1.9rem; }
}


/* --- 7. print ----------------------------------------------------------- */

@media print {
  .toc,
  .masthead,
  .note-permalink {
    display: none;
  }

  .sidenote {
    display: block;
    float: none;
    width: auto;
    margin: 0.6rem 0;
    font-size: 0.8rem;
    border-left: 2px solid var(--rule);
    padding-left: 0.6rem;
  }

  .layout {
    display: block;
    max-width: none;
  }
}