/* ── Reset ─────────────────────────────────────── */
*, *::before, *::after { margin: 0; padding: 0; box-sizing: border-box; }

/* ── Root variables ────────────────────────────── */
:root {
  --bg:    #1a1a2e;
  --fg:    #e0e0e0;
  --acc:   #e94560;
  --acc2:  #0f3460;
  --mono:  "Berkeley Mono", "Iosevka", "Fira Code", monospace;
  --serif: "Newsreader", "Charter", Georgia, serif;
  --max-w: 52rem;
}

body {
  font: 1.05rem/1.7 var(--serif);
  color: var(--fg);
  background: var(--bg);
  max-width: var(--max-w);
  margin: 2rem auto;
  padding: 0 1.5rem;
}

/* ── Typography ────────────────────────────────── */
h1, h2, h3 { font-family: var(--mono); color: var(--acc); margin: 1.8rem 0 0.6rem; }
h1 { font-size: 1.8rem; border-bottom: 2px solid var(--acc2); padding-bottom: 0.3rem; }
h2 { font-size: 1.35rem; }
a  { color: var(--acc); text-decoration: none; }
a:hover { text-decoration: underline; }

code, pre { font-family: var(--mono); font-size: 0.92rem; }
pre {
  background: #0f0f23;
  padding: 1rem;
  overflow-x: auto;
  border-left: 3px solid var(--acc);
  margin: 1rem 0;
}
code { background: #0f0f23; padding: 0.15em 0.35em; border-radius: 3px; }
pre code { background: none; padding: 0; }

blockquote {
  border-left: 3px solid var(--acc2);
  padding-left: 1rem;
  color: #aaa;
  margin: 1rem 0;
}

/* ── Nav ───────────────────────────────────────── */
nav { display: flex; gap: 1.5rem; margin-bottom: 2rem; font-family: var(--mono); font-size: 0.85rem; flex-wrap: wrap; }
nav .breadcrumb .sep { color: #555; margin: 0 0.2rem; }
nav .lang-switch { margin-left: auto; display: flex; gap: 0.5rem; }
nav .lang-switch a { opacity: 0.5; }
nav .lang-switch a.active { opacity: 1; text-decoration: underline; }

/* ── Course pages ──────────────────────────────── */
.course-desc { color: #aaa; font-size: 1.1rem; margin-bottom: 1.5rem; font-style: italic; }
.topic-list h3 { font-size: 1.1rem; margin: 1rem 0 0.2rem; }

/* ── Media embeds ──────────────────────────────── */
video, iframe {
  display: block;
  width: 100%;
  max-width: 100%;
  margin: 1.5rem 0;
  border: 1px solid var(--acc2);
}

/* ── Quiz styling ──────────────────────────────── */
.quiz       { border: 1px solid var(--acc2); padding: 1.2rem; margin: 1.5rem 0; }
.quiz h3    { margin-top: 0; }
.quiz label { display: block; padding: 0.3rem 0; cursor: pointer; }
.quiz .feedback { margin-top: 0.8rem; font-weight: bold; }
.quiz .feedback.correct   { color: #4caf50; }
.quiz .feedback.incorrect { color: var(--acc); }
.quiz button {
  margin-top: 0.8rem;
  padding: 0.4rem 1.2rem;
  background: var(--acc);
  color: #fff;
  border: none;
  cursor: pointer;
  font-family: var(--mono);
}

/* ── Table of contents / index ─────────────────── */
.toc ol { list-style: none; counter-reset: module; }
.toc li { counter-increment: module; margin: 0.5rem 0; }
.toc li::before {
  content: counter(module, decimal-leading-zero) " ";
  color: var(--acc);
  font-family: var(--mono);
}

footer { margin-top: 3rem; color: #555; font-size: 0.8rem; }

/* ── KaTeX overrides ───────────────────────────── */
.katex-display { margin: 1.2rem 0; overflow-x: auto; overflow-y: hidden; }
.katex { font-size: 1.1em; }