/* ── Base ── */
body {
  font-family: Georgia, "Times New Roman", serif;
  max-width: 860px;
  margin: 0 auto;
  padding: 20px 30px;
  color: #222;
  line-height: 1.65;
}

/* ── Site nav ── */
nav ul {
  list-style: none; padding: 0;
  display: flex; gap: 1.5rem;
  border-bottom: 1px solid #ccc;
  padding-bottom: 10px; margin-bottom: 1.5rem;
}
nav ul li a { text-decoration: none; color: #555; }
nav ul li a:hover { color: #000; }

/* ── Lecture nav ── */
.lecture-nav {
  display: flex; justify-content: space-between;
  margin: 1.5rem 0; font-size: 0.9rem;
}
.lecture-nav a { text-decoration: none; color: #0066cc; }
.lecture-nav a:hover { text-decoration: underline; }

/* ── Headings ── */
h1.title { font-size: 1.6rem; margin-bottom: 0.2rem; }
p.author { color: #555; margin-top: 0; }
h1 { font-size: 1.4rem; border-bottom: 1px solid #ddd;
     padding-bottom: 4px; margin-top: 2rem; }
h2 { font-size: 1.2rem; margin-top: 1.5rem; }
h3 { font-size: 1.05rem; }

/* ── Theorem boxes ── */
.definition {
  border-left: 4px solid #1a5ca8;
  background: #f0f5ff;
  padding: 10px 16px;
  margin: 1.2rem 0;
  border-radius: 0 4px 4px 0;
}
.theorem, .lemma, .proposition, .corollary {
  border-left: 4px solid #b83200;
  background: #fff5f0;
  padding: 10px 16px;
  margin: 1.2rem 0;
  border-radius: 0 4px 4px 0;
}
.example {
  border-left: 4px solid #1a7a44;
  background: #f0fff5;
  padding: 10px 16px;
  margin: 1.2rem 0;
  border-radius: 0 4px 4px 0;
}
.remark {
  border-left: 4px solid #996600;
  background: #fffdf0;
  padding: 10px 16px;
  margin: 1.2rem 0;
  border-radius: 0 4px 4px 0;
}
.proof {
  border-left: 4px solid #888;
  background: #fafafa;
  padding: 10px 16px;
  margin: 1.2rem 0;
  border-radius: 0 4px 4px 0;
  font-style: italic;
}
.proof p:last-child { text-align: right; font-style: normal; }

/* ── Algorithm box ── */
.algorithm {
  border: 1px solid #aaa;
  background: #f9f9f9;
  padding: 10px 16px;
  margin: 1.2rem 0;
  font-family: monospace;
  white-space: pre-wrap;
}

/* ── Math overflow ── */
.math.display { overflow-x: auto; }
mjx-container { overflow-x: auto; max-width: 100%; }