/* ============================================================
   Lecture-note archive — هـ / Electric Monotone
   Matches hodahashemi.com v3: one hue (#0038ff), ink & paper.
   ============================================================ */
:root {
  --blue: #0038ff;
  --blue-strong: #002ccc;
  --ink: #0a0c1c;
  --muted: #565b76;
  --paper: #ffffff;
  --paper-subtle: #f5f7ff;
  --soft: rgba(0, 56, 255, 0.07);
  --line: rgba(10, 12, 28, 0.11);
  --mono: ui-monospace, "SF Mono", Menlo, monospace;
  --sans: ui-sans-serif, system-ui, -apple-system, "Segoe UI", sans-serif;
}

* { box-sizing: border-box; }

html { scroll-behavior: smooth; scroll-padding-top: 90px; }

body {
  margin: 0;
  background: var(--paper);
  color: var(--ink);
  font-family: var(--sans);
  line-height: 1.75;
  font-size: 17px;
  -webkit-font-smoothing: antialiased;
  text-rendering: optimizeLegibility;
}

::selection { background: var(--blue); color: #fff; }

/* ---------------- header (injected by scripts.js) ---------------- */
.site-header {
  position: sticky;
  top: 0;
  z-index: 50;
  background: rgba(255, 255, 255, 0.82);
  backdrop-filter: blur(14px) saturate(1.3);
  -webkit-backdrop-filter: blur(14px) saturate(1.3);
  border-bottom: 1px solid var(--line);
}

.site-nav {
  max-width: 1080px;
  margin: 0 auto;
  padding: 14px 24px;
  display: flex;
  align-items: center;
  justify-content: space-between;
  gap: 16px;
  flex-wrap: wrap;
}

.brand-mark {
  display: inline-flex;
  align-items: center;
  gap: 10px;
  text-decoration: none;
  border-bottom: none;
  color: var(--ink);
  font-weight: 650;
  font-size: 15px;
  letter-spacing: -0.01em;
}
.brand-mark img { border-radius: 8px; }

.nav-links {
  display: flex;
  align-items: center;
  gap: 4px;
  flex-wrap: wrap;
}
.nav-links a {
  font-family: var(--mono);
  font-size: 11.5px;
  font-weight: 500;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  color: var(--muted);
  text-decoration: none;
  border-bottom: none;
  padding: 7px 11px;
  border-radius: 8px;
  transition: color 140ms ease, background 140ms ease;
}
.nav-links a:hover { color: var(--blue); background: var(--soft); }
.nav-links a.active { color: var(--blue); background: var(--soft); }
.external-links { display: inline-flex; gap: 4px; padding-left: 8px; margin-left: 4px; border-left: 1px solid var(--line); }

/* ---------------- article body ---------------- */
main {
  max-width: 760px;
  margin: 0 auto;
  padding: 56px 24px 100px;
}

h1 {
  font-size: clamp(34px, 6vw, 52px);
  line-height: 1.05;
  letter-spacing: -0.022em;
  margin: 24px 0 8px;
}
/* mono kicker above the title */
h1::before {
  content: "// lecture notes — hoda hashemi";
  display: block;
  font-family: var(--mono);
  font-size: 12px;
  font-weight: 500;
  letter-spacing: 0.16em;
  text-transform: uppercase;
  color: var(--blue);
  margin-bottom: 18px;
}

h2 {
  font-size: clamp(22px, 3.4vw, 30px);
  letter-spacing: -0.018em;
  line-height: 1.15;
  margin: 64px 0 12px;
  padding-top: 22px;
  border-top: 1px solid var(--line);
}
/* numbered section markers */
body { counter-reset: sec; }
h2::before {
  counter-increment: sec;
  content: "0" counter(sec);
  display: block;
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: 0.16em;
  color: var(--blue);
  margin-bottom: 8px;
}

h3 { font-size: 20px; letter-spacing: -0.01em; margin: 40px 0 8px; }

p { margin: 0 0 18px; color: var(--ink); text-wrap: pretty; }

a {
  color: var(--blue);
  text-decoration: none;
  border-bottom: 1px solid rgba(0, 56, 255, 0.3);
  transition: border-color 140ms ease, color 140ms ease;
}
a:hover { color: var(--blue-strong); border-bottom-color: currentColor; }

ul, ol { padding-left: 24px; margin: 0 0 18px; }
li { margin: 6px 0; }

strong { font-weight: 650; }

code, pre {
  font-family: var(--mono);
  font-size: 0.88em;
  background: var(--paper-subtle);
  border: 1px solid var(--line);
  border-radius: 6px;
}
code { padding: 0.15em 0.4em; }
pre { padding: 16px 18px; overflow-x: auto; line-height: 1.6; }
pre code { border: 0; background: none; padding: 0; }

/* ---------------- equations ---------------- */
div[id^="eq-"], div[id^="differential-"] {
  margin: 26px 0;
  padding: 18px 20px;
  background: var(--paper-subtle);
  border: 1px solid var(--line);
  border-left: 3px solid var(--blue);
  border-radius: 10px;
  overflow-x: auto;
}
div[id^="eq-"]:target, div[id^="differential-"]:target {
  border-color: var(--blue);
  background: var(--soft);
}
mjx-container { margin: 0 !important; }
mjx-container[display="true"] { overflow-x: auto; overflow-y: hidden; padding: 4px 0; }

/* ---------------- images ---------------- */
img { max-width: 100%; height: auto; }
.center-image {
  display: block;
  margin: 32px auto;
  border: 1px solid var(--line);
  border-radius: 12px;
  padding: 10px;
  background: #fff;
}
.responsive-img { width: 100%; height: auto; }

/* ---------------- lab grids (guide pages) ---------------- */
.lab-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 14px;
  margin: 28px 0;
}
.lab-card {
  border: 1px solid var(--line);
  border-radius: 12px;
  background: var(--paper);
  padding: 18px 20px;
  transition: border-color 160ms ease, transform 160ms ease, box-shadow 160ms ease;
}
.lab-card:hover {
  border-color: rgba(0, 56, 255, 0.45);
  transform: translateY(-2px);
  box-shadow: 0 14px 40px -14px rgba(0, 56, 255, 0.25);
}

/* ---------------- reveal (scripts.js) ---------------- */
.reveal { opacity: 0; transform: translateY(14px); transition: opacity 560ms ease, transform 560ms ease; }
.reveal.is-visible { opacity: 1; transform: none; }

/* ---------------- back-to-articles footer (injected) ---------------- */
.note-foot {
  max-width: 760px;
  margin: 0 auto;
  padding: 0 24px 80px;
}
.note-foot a {
  display: inline-flex;
  align-items: center;
  gap: 8px;
  font-family: var(--mono);
  font-size: 12px;
  letter-spacing: 0.12em;
  text-transform: uppercase;
  border: 1px solid var(--line);
  border-radius: 10px;
  padding: 12px 18px;
  color: var(--blue);
  background: var(--paper);
}
.note-foot a:hover { background: var(--blue); color: #fff; border-color: var(--blue); }

@media (max-width: 640px) {
  body { font-size: 16px; }
  .external-links { display: none; }
}

@media (prefers-reduced-motion: reduce) {
  html { scroll-behavior: auto; }
  .reveal { opacity: 1; transform: none; transition: none; }
  * { transition-duration: 0.01ms !important; }
}