/* ============================================================
   Base styles — לייאאוט, RTL, FHD optimization
   target: 1920×1080 projector / 15.6" laptop screen
   ============================================================ */

@import url('https://fonts.googleapis.com/css2?family=Heebo:wght@300;400;500;600;700;800&display=swap');

* {
  box-sizing: border-box;
}

html, body {
  margin: 0;
  padding: 0;
  background: var(--bg-page);
  color: var(--text-default);
  font-family: 'Heebo', system-ui, -apple-system, sans-serif;
  font-size: 18px;
  line-height: 1.6;
  direction: rtl;
}

main {
  max-width: 1600px;
  margin: 0 auto;
  padding: 24px 48px 64px 48px;
}

/* --- Headings --- */
h1, h2, h3, h4 {
  margin: 0;
  line-height: 1.3;
  color: var(--text-title);
}

h1 { font-size: 40px; font-weight: 700; }
h2 { font-size: 28px; font-weight: 600; }
h3 { font-size: 22px; font-weight: 600; }
h4 { font-size: 18px; font-weight: 600; }

/* --- LTR overrides for code, formulas, English terms --- */
code, pre, .ltr {
  direction: ltr;
  unicode-bidi: isolate;
  font-family: 'Consolas', 'Monaco', monospace;
}

/* --- KaTeX math: isolate from RTL parent so super/subscripts render correctly ---
   Without this, $R^2$ in an RTL container renders as ²R because the bidi algorithm
   reorders the absolutely-positioned msupsub element relative to its base. --- */
.katex, .katex-display {
  direction: ltr;
  unicode-bidi: isolate;
}
.katex-display {
  text-align: center;
}

pre {
  background: var(--bg-soft);
  border: 1px solid var(--border-soft);
  border-radius: 8px;
  padding: 12px 16px;
  overflow-x: auto;
  font-size: 16px;
}

/* --- Header / nav --- */
header.lesson-nav {
  display: flex;
  justify-content: space-between;
  align-items: center;
  padding: 12px 24px;
  background: var(--bg-banner);
  border-bottom: 2px solid var(--border-banner);
  font-size: 16px;
}

header.lesson-nav a {
  color: var(--text-body);
  text-decoration: none;
  font-weight: 500;
}

header.lesson-nav a:hover {
  text-decoration: underline;
}

header.lesson-nav .lesson-name {
  font-weight: 700;
  color: var(--text-title);
}

/* --- Block sections --- */
section.block {
  margin: 36px 0;
  scroll-margin-top: 60px;
}

/* --- Footer --- */
footer.lesson-footer {
  margin-top: 64px;
  padding: 16px 24px;
  border-top: 1px solid var(--border-soft);
  text-align: center;
  font-size: 14px;
  color: var(--text-muted);
}

/* --- Responsive: 15.6" laptop (1366×768) fallback --- */
@media (max-width: 1400px) {
  main { padding: 20px 32px 48px 32px; }
  html, body { font-size: 16px; }
  h1 { font-size: 34px; }
  h2 { font-size: 24px; }
  h3 { font-size: 20px; }
}

/* --- Responsive: tablet (≤768px) --- */
@media (max-width: 768px) {
  main { padding: 16px 16px 36px 16px; }
  html, body { font-size: 15px; line-height: 1.55; }
  h1 { font-size: 26px; }
  h2 { font-size: 20px; }
  h3 { font-size: 17px; }
  h4 { font-size: 16px; }

  header.lesson-nav {
    flex-wrap: wrap;
    padding: 10px 14px;
    font-size: 13px;
    gap: 6px;
    justify-content: center;
  }
  header.lesson-nav .lesson-name {
    flex-basis: 100%;
    text-align: center;
    order: -1;
    font-size: 14px;
  }

  footer.lesson-footer {
    margin-top: 36px;
    padding: 12px 16px;
    font-size: 12px;
  }

  pre { font-size: 14px; padding: 10px 12px; }
}

/* --- Responsive: phone (≤480px) --- */
@media (max-width: 480px) {
  main { padding: 12px 12px 28px 12px; }
  html, body { font-size: 14px; }
  h1 { font-size: 22px; }
  h2 { font-size: 18px; }
  h3 { font-size: 16px; }

  pre { font-size: 13px; padding: 8px 10px; }
}

/* --- Print mode (for handouts) --- */
@media print {
  header.lesson-nav, .code-switch { display: none; }
  main { max-width: 100%; padding: 0; }
}