/* ---------- Tokens ---------- */
:root {
  --bg: #ffffff;
  --surface: #f8fafc;
  --text: #1e293b;
  --muted: #475569;            /* LaTeX "secondary" */
  --border: #e2e8f0;
  --primary: #2563eb;          /* LaTeX "primary" */
  --a1: #10b981;               /* accent1: green, case 1 */
  --a2: #ef4444;               /* accent2: red, case 3 */
  --a3: #f59e0b;               /* accent3: amber, case 2 */
  --a1-ink: #047857;
  --a2-ink: #b91c1c;
  --a3-ink: #b45309;
  --c2-blue: #4a76c1;          /* array boxes */
  --c2-light: #badfe9;         /* split wedges */
  --c2-border: #2b4c86;
  --ink: #1e293b;              /* figure strokes */
  --header-h: 60px;
  color-scheme: light;
}
@media (prefers-color-scheme: dark) {
  :root:not([data-theme="light"]) {
    --bg: #0f172a;
    --surface: #1e293b;
    --text: #e2e8f0;
    --muted: #94a3b8;
    --border: #334155;
    --primary: #60a5fa;
    --a1-ink: #34d399;
    --a2-ink: #f87171;
    --a3-ink: #fbbf24;
    --c2-blue: #4a76c1;
    --c2-light: #2d4f66;
    --c2-border: #93b4ea;
    --ink: #cbd5e1;
    color-scheme: dark;
  }
}
:root[data-theme="dark"] {
  --bg: #0f172a;
  --surface: #1e293b;
  --text: #e2e8f0;
  --muted: #94a3b8;
  --border: #334155;
  --primary: #60a5fa;
  --a1-ink: #34d399;
  --a2-ink: #f87171;
  --a3-ink: #fbbf24;
  --c2-blue: #4a76c1;
  --c2-light: #2d4f66;
  --c2-border: #93b4ea;
  --ink: #cbd5e1;
  color-scheme: dark;
}

/* ---------- Base ---------- */
* { box-sizing: border-box; }
html { scroll-padding-top: calc(var(--header-h) + 16px); }
body {
  margin: 0;
  background: var(--bg);
  color: var(--text);
  font-family: "Noto Sans", system-ui, sans-serif;
  font-size: 17px;
  line-height: 1.65;
  -webkit-text-size-adjust: 100%;
}
html[lang="he"] body { font-family: "Noto Sans Hebrew", "Noto Sans", system-ui, sans-serif; }
a { color: var(--primary); }
strong { font-weight: 700; }

/* Math always runs left to right, even inside Hebrew text */
.katex { direction: ltr; unicode-bidi: isolate; font-size: 1.08em; }
.katex-display { direction: ltr; overflow-x: auto; overflow-y: hidden; padding: 4px 0; }

/* ---------- Header ---------- */
.topbar {
  position: sticky; top: 0; z-index: 10;
  background: color-mix(in srgb, var(--bg) 88%, transparent);
  backdrop-filter: blur(8px);
  border-bottom: 1px solid var(--border);
}
.topbar-inner {
  max-width: 1200px; margin: 0 auto;
  min-height: 60px;
  padding: 8px 16px;
  display: flex; align-items: center; justify-content: space-between; gap: 12px;
  flex-wrap: wrap;
}
.brand { font-weight: 700; color: var(--text); text-decoration: none; font-size: 1rem; }
.controls { display: flex; gap: 8px; align-items: center; flex-wrap: wrap; }
.seg {
  display: inline-flex; border: 1px solid var(--border); border-radius: 8px; overflow: hidden;
  background: var(--surface);
}
.seg button {
  font: inherit; font-size: 0.875rem; padding: 5px 12px;
  border: 0; background: transparent; color: var(--muted); cursor: pointer;
}
.seg button + button { border-inline-start: 1px solid var(--border); }
.seg button[aria-pressed="true"] { background: var(--primary); color: #fff; font-weight: 600; }
.seg button:focus-visible, .pdf-btn:focus-visible { outline: 2px solid var(--primary); outline-offset: 2px; }
.pdf-btn {
  display: inline-flex; align-items: center; gap: 6px;
  font-size: 0.875rem; padding: 5px 12px; border-radius: 8px;
  border: 1px solid var(--border); color: var(--text); text-decoration: none; background: var(--surface);
}
.pdf-btn:hover { border-color: var(--primary); }

/* ---------- Layout ---------- */
.layout {
  max-width: 1200px; margin: 0 auto; padding: 0 16px;
  display: grid; grid-template-columns: 240px minmax(0, 1fr); gap: 48px;
}
main { min-width: 0; max-width: 780px; padding: 24px 0 64px; }
.toc { position: sticky; top: calc(var(--header-h) + 16px); align-self: start; padding-top: 32px; font-size: 0.875rem; max-height: calc(100vh - var(--header-h) - 32px); overflow-y: auto; }
.toc summary { font-weight: 700; text-transform: uppercase; letter-spacing: .06em; font-size: .75rem; color: var(--muted); cursor: pointer; margin-bottom: 8px; }
.toc ol { list-style: none; margin: 0; padding: 0; }
.toc li a { display: block; padding: 4px 10px; color: var(--muted); text-decoration: none; border-inline-start: 2px solid var(--border); }
.toc li.sub a { padding-inline-start: 22px; font-size: .8125rem; }
.toc li a:hover { color: var(--text); }
.toc li a.active { color: var(--primary); border-inline-start-color: var(--primary); }

@media (max-width: 900px) {
  .layout { grid-template-columns: minmax(0, 1fr); gap: 0; }
  .toc { position: static; max-height: none; padding-top: 16px; }
  .toc details { border: 1px solid var(--border); border-radius: 10px; padding: 8px 12px; background: var(--surface); }
  .toc summary { margin: 0; }
  .toc details[open] summary { margin-bottom: 8px; }
}

/* ---------- Audience switching ---------- */
html[data-mode="student"] [data-audience="educator"],
html[data-mode="educator"] [data-audience="student"] { display: none !important; }

/* ---------- Typography ---------- */
.hero { padding: 24px 0 8px; border-bottom: 1px solid var(--border); margin-bottom: 8px; }
.hero h1 { font-size: clamp(1.9rem, 5vw, 2.6rem); line-height: 1.15; margin: 0 0 8px; letter-spacing: -0.01em; }
html[lang="he"] .hero h1 { letter-spacing: 0; }
.hero .subtitle { color: var(--muted); margin: 0 0 16px; font-size: 1.1rem; }
.shape-strip { display: flex; gap: 16px; align-items: center; margin: 8px 0 12px; }
.shape-strip svg { width: 44px; height: 44px; }
h2 { font-size: 1.6rem; line-height: 1.25; margin: 48px 0 12px; padding-top: 8px; }
h3 { font-size: 1.25rem; margin: 32px 0 8px; }
h4 { font-size: 1.05rem; margin: 24px 0 6px; }
p { margin: 0 0 14px; }
ul, ol { padding-inline-start: 24px; margin: 0 0 14px; }
li { margin-bottom: 6px; }
li > ul { margin-top: 6px; }

/* ---------- Condition boxes (tcolorbox) ---------- */
.condition { border: 1.5px solid var(--c); border-radius: 8px; overflow: hidden; margin: 12px 0 18px; background: color-mix(in srgb, var(--c) 10%, var(--bg)); }
.condition .cond-title { background: var(--c); color: #fff; font-weight: 700; padding: 4px 14px; font-size: .95rem; }
.condition .cond-body { padding: 10px 14px; }
.case-1 { --c: var(--a1); --c-ink: var(--a1-ink); }
.case-2 { --c: var(--a3); --c-ink: var(--a3-ink); }
.case-3 { --c: var(--a2); --c-ink: var(--a2-ink); }
.case h3 { color: var(--c-ink); }

/* ---------- Figures ---------- */
figure { margin: 24px 0 28px; }
figcaption { color: var(--muted); font-size: .9rem; margin-top: 10px; text-align: center; }
.fig-scroll { overflow-x: auto; -webkit-overflow-scrolling: touch; }
.fig-canvas { position: relative; container-type: inline-size; direction: ltr; margin: 0 auto; }
.fig-canvas svg { display: block; width: 100%; height: auto; overflow: visible; }
.fig-label {
  position: absolute; white-space: nowrap; line-height: 1.2; color: var(--text);
  font-size: calc(var(--fs, 2.2) * 1cqw);
}
.fig-label .katex { font-size: 1.05em; }
.fig-label.bg { background: var(--bg); padding: 0 .2em; }
.fig-label[lang="he"] { direction: rtl; unicode-bidi: isolate; font-family: "Noto Sans Hebrew", "Noto Sans", sans-serif; }
.fig-tree { min-width: 680px; }

/* SVG paint classes */
.s-ink { stroke: var(--ink); fill: none; }
.s-dot { stroke: var(--ink); fill: none; stroke-dasharray: 2 3; }
.f-ink { fill: var(--ink); }
.box { fill: var(--c2-blue); stroke: var(--c2-border); stroke-width: 1.6; }
.wedge { fill: var(--c2-light); }
.shape-fill { fill: color-mix(in srgb, var(--c) 20%, var(--bg)); stroke: var(--c); stroke-width: 2; }
.shape-level { stroke: color-mix(in srgb, var(--c) 50%, var(--bg)); stroke-dasharray: 6 4; stroke-width: 1.2; }
.shape-arrow { stroke: var(--muted); stroke-width: 2.2; fill: none; }
.shape-arrow-head { fill: var(--muted); }

/* ---------- Mnemonic strip ---------- */
.mnemonic { display: grid; grid-template-columns: repeat(3, minmax(0, 1fr)); gap: 12px; margin: 20px 0 8px; }
.mnemonic a { display: block; text-decoration: none; color: inherit; border: 1px solid var(--border); border-radius: 10px; padding: 12px; background: var(--surface); text-align: center; }
.mnemonic a:hover { border-color: var(--c); }
.mnemonic svg { width: 64px; height: 48px; display: block; margin: 0 auto 6px; }
.mnemonic .m-name { font-weight: 700; color: var(--c-ink); display: block; }
.mnemonic .m-rel { font-size: .9rem; color: var(--muted); display: block; }
@media (max-width: 520px) { .mnemonic { grid-template-columns: minmax(0, 1fr); } }

/* ---------- Footer ---------- */
.footer { border-top: 1px solid var(--border); color: var(--muted); font-size: .875rem; text-align: center; padding: 24px 16px 40px; }
.loading { color: var(--muted); }

@media (max-width: 600px) {
  body { font-size: 16px; }
  .brand { font-size: .95rem; }
  h2 { font-size: 1.4rem; }
}
@media print {
  .topbar, .toc, .footer { display: none; }
  .layout { display: block; }
}

/* Display line mixing Hebrew words and math */
.eq-he { text-align: center; margin: 16px 0; font-size: 1.05rem; }
/* Embedded English inside Hebrew text keeps its own direction */
[dir="rtl"] [lang="en"] { unicode-bidi: isolate; }

/* Educator tip boxes (LaTeX "educatortip": primary frame, light primary background) */
.edu-tip { --c: var(--primary); background: color-mix(in srgb, var(--primary) 6%, var(--bg)); margin: 16px 0 22px; }
.edu-tip .cond-body ul { margin: 0; }
.edu-tip .cond-body li:last-child { margin-bottom: 0; }
.hero .byline { margin: -8px 0 16px; font-weight: 600; color: var(--muted); }

/* ---------- Collapsible sections ---------- */
details.sec > summary {
  list-style: none; cursor: pointer;
  display: flex; align-items: center; gap: 10px;
  border-radius: 6px;
}
details.sec > summary::-webkit-details-marker { display: none; }
details.sec > summary > h2, details.sec > summary > h3 { margin: 0; }
details.sec-2 > summary { margin: 40px 0 12px; padding-top: 8px; }
details.sec-3 > summary { margin: 28px 0 8px; }
/* Chevron: points down when open, toward the reading direction when closed */
details.sec > summary::before {
  content: ""; flex: none; width: .5em; height: .5em;
  border-right: 2px solid var(--muted); border-bottom: 2px solid var(--muted);
  transform: rotate(45deg); transition: transform .15s ease; margin-top: -0.2em;
}
details.sec:not([open]) > summary::before { transform: rotate(-45deg); margin-top: 0; }
[dir="rtl"] details.sec:not([open]) > summary::before { transform: rotate(135deg); }
details.sec > summary:hover::before { border-color: var(--primary); }
details.sec > summary:hover > h2, details.sec > summary:hover > h3 { color: var(--primary); }
.case details.sec > summary:hover > h3 { color: var(--c-ink); text-decoration: underline; text-underline-offset: 4px; }
details.sec > summary:focus-visible { outline: 2px solid var(--primary); outline-offset: 4px; }
.case > details.sec-3:first-child > summary { margin-top: 32px; }

.toggle-all {
  margin-top: 12px; font: inherit; font-size: .8125rem; color: var(--primary);
  background: none; border: 1px solid var(--border); border-radius: 6px; padding: 4px 10px; cursor: pointer;
}
.toggle-all:hover { border-color: var(--primary); }
@media print { details.sec > summary::before { display: none; } }