/* IOAI Guide — foundation and layout.
   Same paper look as the main SOTA site: STIX Two Text, ink on white, hairline rules,
   red for the current place, blue for links. Components live in components.css. */

:root {
  --paper: #FFFFFF;
  --ink: #16161D;
  --graphite: #5F6070;
  --hairline: #DCDCE3;
  --plate: #F5F5F8;
  --red: #B31B1B;
  --blue: #1F48C7;

  /* Syllabus categories */
  --cat-theory: #5F6070;
  --cat-practice: #1F48C7;
  --cat-both: #B31B1B;

  --serif: "STIX Two Text", "STIX Two", Cambria, "Times New Roman", serif;
  --mono: ui-monospace, "SF Mono", Menlo, Consolas, "Liberation Mono", monospace;

  --topbar-h: 58px;
  --sidebar-w: 288px;
  --toc-w: 216px;
  --measure: 720px;

  color-scheme: light;
}

/* ---------- base ---------- */

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

html {
  -webkit-text-size-adjust: 100%;
  scroll-padding-top: calc(var(--topbar-h) + 24px);
}

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--serif);
  font-size: 18px;
  line-height: 1.6;
  font-variant-numeric: lining-nums;
  text-rendering: optimizeLegibility;
}

h1, h2, h3, h4, p, ol, ul, dl, dd, figure, table { margin: 0; }

img { display: block; max-width: 100%; height: auto; }

a { color: var(--blue); text-decoration: none; }
a:hover { text-decoration: underline; text-underline-offset: 2px; }
:focus-visible { outline: 2px solid var(--red); outline-offset: 2px; }

::selection { background: color-mix(in srgb, var(--red) 20%, transparent); }

.num { font-variant-numeric: tabular-nums; }

.visually-hidden {
  position: absolute;
  width: 1px;
  height: 1px;
  overflow: hidden;
  clip-path: inset(50%);
  white-space: nowrap;
}

.skip {
  position: absolute;
  left: -9999px;
  top: 8px;
  z-index: 100;
  background: var(--paper);
  color: var(--ink);
  border: 1px solid var(--ink);
  padding: 6px 10px;
}
.skip:focus { left: 8px; }

/* Boxed link, like hyperref's red link borders */
.box {
  display: inline-block;
  border: 1px solid var(--red);
  color: var(--ink);
  padding: 2px 10px 3px;
  line-height: 1.35;
}
.box:hover {
  background: var(--red);
  color: var(--paper);
  text-decoration: none;
}

/* ---------- top bar ---------- */

.topbar {
  position: sticky;
  top: 0;
  z-index: 40;
  height: var(--topbar-h);
  display: flex;
  align-items: center;
  gap: 12px 24px;
  padding-inline: 20px;
  background: var(--paper);
  border-bottom: 1px solid var(--hairline);
}

.menu-toggle {
  display: none;
  align-items: center;
  font: inherit;
  font-size: 15px;
  color: var(--ink);
  background: none;
  border: 1px solid var(--hairline);
  padding: 3px 10px 4px;
  cursor: pointer;
}
.menu-toggle[aria-expanded="true"] { border-color: var(--ink); }

.brand {
  display: inline-flex;
  align-items: center;
  gap: 12px;
  color: var(--ink);
  flex: none;
}
.brand:hover { text-decoration: none; }
.brand-mark {
  display: block;
  width: 30px;
  height: 15px;
  fill: currentColor;
  shape-rendering: crispEdges;
}
.brand-name {
  font-size: 20px;
  font-weight: 700;
  font-variant-caps: all-small-caps;
  letter-spacing: .08em;
  white-space: nowrap;
}

.search {
  flex: 1 1 auto;
  min-width: 0;
  max-width: 440px;
  margin-left: auto;
}

.top-links {
  display: flex;
  align-items: center;
  gap: 20px;
  font-size: 16px;
  flex: none;
}
.top-links a:not(.box) { color: var(--ink); }

/* ---------- three-column layout ---------- */

.layout {
  display: grid;
  grid-template-columns: var(--sidebar-w) minmax(0, 1fr) var(--toc-w);
  max-width: 1480px;
  margin-inline: auto;
}

.main {
  min-width: 0;
  padding: 48px clamp(20px, 5vw, 72px) 112px;
}

.article {
  max-width: var(--measure);
  margin-inline: auto;
}

/* ---------- sidebar ---------- */

.sidebar {
  position: sticky;
  top: var(--topbar-h);
  height: calc(100vh - var(--topbar-h));
  overflow-y: auto;
  overscroll-behavior: contain;
  padding: 24px 16px 48px 24px;
  border-right: 1px solid var(--hairline);
  background: var(--paper);
}

.side-version {
  font-size: 13.5px;
  color: var(--graphite);
  margin-bottom: 12px;
}

.side-part {
  border-top: 1px solid var(--hairline);
  padding-block: 8px 12px;
}

.side-part > summary {
  list-style: none;
  cursor: pointer;
  display: grid;
  grid-template-columns: 1.5em minmax(0, 1fr) 1em;
  align-items: baseline;
  gap: 4px;
  padding-block: 6px;
  font-size: 15.5px;
  font-weight: 700;
  line-height: 1.3;
}
.side-part > summary::-webkit-details-marker { display: none; }
.side-part > summary::after {
  content: "+";
  color: var(--graphite);
  font-weight: 400;
  text-align: right;
}
.side-part[open] > summary::after { content: "−"; }

.side-topic {
  display: flex;
  gap: .6em;
  margin: 14px 0 4px;
  font-size: 14px;
  font-variant-caps: all-small-caps;
  letter-spacing: .06em;
  color: var(--graphite);
}

.side-modules {
  list-style: none;
  padding: 0;
}

.side-modules a {
  display: grid;
  grid-template-columns: 8px 2.4em minmax(0, 1fr) auto;
  align-items: baseline;
  gap: 8px;
  padding: 4px 6px 4px 6px;
  font-size: 14.5px;
  line-height: 1.3;
  color: var(--ink);
}
.side-modules a:hover {
  background: var(--plate);
  text-decoration: none;
}
.side-modules a[aria-current="page"] {
  background: var(--plate);
  box-shadow: inset 2px 0 0 var(--red);
}
.side-modules .num {
  font-size: 12.5px;
  color: var(--graphite);
}

/* Progress: an empty circle, half-filled while reading, filled when done */
.status-dot {
  align-self: start;
  margin-top: .38em;
  width: 8px;
  height: 8px;
  border-radius: 50%;
  border: 1px solid var(--hairline);
}
.is-reading .status-dot {
  border-color: var(--ink);
  background: linear-gradient(90deg, var(--ink) 50%, transparent 50%);
}
.is-done .status-dot {
  border-color: var(--ink);
  background: var(--ink);
}

/* T / P / B category letters */
.cat {
  align-self: start;
  margin-top: 1px;
  min-width: 1.5em;
  padding: 0 3px;
  border: 1px solid currentColor;
  font-size: 11px;
  line-height: 1.35;
  text-align: center;
}
.cat-theory { color: var(--cat-theory); }
.cat-practice { color: var(--cat-practice); }
.cat-both { color: var(--cat-both); }

.side-links {
  list-style: none;
  display: grid;
  gap: 6px;
  margin-top: 8px;
  padding: 16px 0 0 6px;
  border-top: 1px solid var(--hairline);
  font-size: 15px;
}

/* ---------- "On this page" rail ---------- */

.toc {
  position: sticky;
  top: var(--topbar-h);
  height: calc(100vh - var(--topbar-h));
  overflow-y: auto;
  padding: 48px 20px 40px 0;
}
.toc:has(.toc-list:empty) { visibility: hidden; }

.toc-title {
  margin: 0 0 8px 13px;
  font-size: 14px;
  font-variant-caps: all-small-caps;
  letter-spacing: .08em;
  color: var(--graphite);
}

.toc-list {
  list-style: none;
  padding: 0;
  border-left: 1px solid var(--hairline);
  font-size: 13.5px;
  line-height: 1.35;
}
.toc-list a {
  display: block;
  margin-left: -1px;
  padding: 4px 0 4px 12px;
  border-left: 2px solid transparent;
  color: var(--graphite);
}
.toc-list .toc-sub a {
  padding-left: 24px;
  font-size: 12.5px;
}
.toc-list a:hover { color: var(--ink); text-decoration: none; }
.toc-list a.is-active {
  color: var(--ink);
  border-left-color: var(--red);
}

.scrim {
  position: fixed;
  inset: var(--topbar-h) 0 0 0;
  z-index: 20;
  background: rgb(22 22 29 / .28);
}

/* ---------- narrower screens ---------- */

@media (max-width: 1200px) {
  .layout { grid-template-columns: var(--sidebar-w) minmax(0, 1fr); }
  .toc { display: none; }
}

@media (max-width: 900px) {
  .layout { grid-template-columns: minmax(0, 1fr); }
  .menu-toggle { display: inline-flex; }
  .sidebar {
    position: fixed;
    top: var(--topbar-h);
    bottom: 0;
    left: 0;
    z-index: 30;
    width: min(88vw, 340px);
    height: auto;
    transform: translateX(-100%);
    transition: transform .2s ease;
  }
  body.menu-open { overflow: hidden; }
  body.menu-open .sidebar {
    transform: none;
    box-shadow: 16px 0 40px rgb(22 22 29 / .14);
  }
  .main { padding-top: 32px; }
}

@media (max-width: 640px) {
  body { font-size: 17px; }
  .topbar { gap: 10px; padding-inline: 16px; }
  .top-links .opt { display: none; }
}

@media (max-width: 460px) {
  .brand-name { display: none; }
}

@media (prefers-reduced-motion: reduce) {
  * { transition: none !important; scroll-behavior: auto !important; }
}