/* ===== BASE ===== */
body {
  font-family: system-ui, -apple-system, Segoe UI, Roboto, Arial, sans-serif;
  margin: 0;
  background: #f8fafc;
  color: #1f2937;
  line-height: 1.6;
}

/* ===== HERO ===== */
.hero {
  text-align: center;
  padding: 70px 20px 50px;
  background: linear-gradient(135deg, #0f172a, #1e3a8a);
  color: white;
}

.hero h1 {
  margin: 0;
  font-size: 2.5rem;
  letter-spacing: 0.5px;
}

.hero .subtitle {
  margin-top: 10px;
  color: #cbd5e1;
  font-size: 1.1rem;
}

/* ===== MAIN LAYOUT ===== */
.math-container {
  max-width: 850px;
  margin: -30px auto 60px;
  padding: 20px;
}

/* intro paragraph */
.math-container > p {
  background: white;
  padding: 20px;
  border-radius: 12px;
  box-shadow: 0 4px 12px rgba(0,0,0,0.05);
  margin-bottom: 40px;
}

/* ===== SECTIONS ===== */
.math-section {
  background: white;
  padding: 25px 25px;
  margin-bottom: 25px;
  border-radius: 12px;
  box-shadow: 0 4px 12px rgba(0,0,0,0.05);
  transition: transform 0.15s ease;
}

.math-section:hover {
  transform: translateY(-2px);
}

.math-section h2 {
  margin-top: 0;
  border-left: 4px solid #38bdf8;
  padding-left: 12px;
  font-size: 1.4rem;
}

/* subtitle inside sections */
.math-section .subtitle {
  color: #6b7280;
  margin-top: -10px;
  margin-bottom: 15px;
  font-size: 0.95rem;
}

/* ===== LISTS ===== */
.math-section ul {
  list-style: none;
  padding: 0;
  margin: 0;
}

.math-section li {
  margin: 12px 0;
}

/* ===== LINKS (IMPROVED VISIBILITY) ===== */
.math-section a {
  display: inline-block;
  color: #2563eb;
  text-decoration: none;
  font-weight: 500;
  padding: 6px 10px;
  border-radius: 6px;
  transition: all 0.2s ease;
}

.math-section a:hover {
  background: #eff6ff;
  color: #1d4ed8;
}

/* ===== FOOTER ===== */
footer {
  text-align: center;
  padding: 30px;
  color: #94a3b8;
  font-size: 0.9rem;
}