* {
  margin: 0;
  padding: 0;
  box-sizing: border-box;
}

body {
  font-family: Georgia, "Times New Roman", serif;
  background: #f7f3eb;
  color: #1f2933;
  line-height: 1.6;
}

.navbar {
  background: #102a43;
  color: white;
  padding: 18px 8%;
  display: flex;
  justify-content: space-between;
  align-items: center;
}

.logo {
  font-size: 22px;
  font-weight: bold;
}

.nav-links {
  list-style: none;
  display: flex;
  gap: 28px;
  flex-wrap: wrap;
}

.nav-links a {
  color: white;
  text-decoration: none;
  font-size: 15px;
}

.nav-links a:hover {
  color: #d4af37;
}

.page-header {
  background: #102a43;
  color: white;
  padding: 70px 8%;
  text-align: center;
}

.page-header h1 {
  font-size: 42px;
  margin-bottom: 15px;
}

.page-header p {
  font-size: 19px;
  color: #e5e7eb;
  max-width: 820px;
  margin: 0 auto;
}

.container {
  max-width: 1100px;
  margin: auto;
  padding: 60px 8%;
}

.card {
  background: white;
  padding: 32px;
  border-radius: 10px;
  box-shadow: 0 8px 24px rgba(16, 42, 67, 0.08);
  margin-bottom: 28px;
}

.card h2,
.card h3 {
  color: #102a43;
  margin-bottom: 15px;
}

.card p,
.card li {
  color: #3e4c59;
  font-size: 17px;
}

.topic-grid,
.lesson-grid {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(230px, 1fr));
  gap: 14px;
  margin-top: 18px;
}

.topic-card,
.lesson-item {
  background: #f7f3eb;
  border-left: 4px solid #d4af37;
  padding: 16px;
  border-radius: 6px;
  color: #243b53;
}

.topic-card a {
  color: #102a43;
  font-weight: bold;
  text-decoration: none;
  border-bottom: 2px solid #d4af37;
}

.topic-card a:hover {
  color: #d4af37;
}

.teaching-list {
  display: grid;
  grid-template-columns: repeat(auto-fit, minmax(240px, 1fr));
  gap: 14px;
  margin-top: 18px;
}

.teaching-column {
  background: #f7f3eb;
  border-left: 4px solid #d4af37;
  padding: 18px;
  border-radius: 6px;
}

.teaching-column h3 {
  font-size: 20px;
  margin-bottom: 10px;
}

.teaching-column ul {
  margin-left: 20px;
}

.teaching-column li {
  margin-bottom: 8px;
}

.subtopic {
  background: #f7f3eb;
  border-left: 4px solid #d4af37;
  padding: 18px;
  border-radius: 6px;
  margin-top: 16px;
}

.subtopic h3 {
  font-size: 21px;
  margin-bottom: 10px;
}

.subtopic ul {
  margin-left: 20px;
}

.subtopic li {
  margin-bottom: 8px;
}

.weight-table {
  width: 100%;
  border-collapse: collapse;
  margin-top: 18px;
}

.weight-table th,
.weight-table td {
  border: 1px solid #e5dccb;
  padding: 12px 14px;
  text-align: left;
}

.weight-table th {
  background: #102a43;
  color: white;
}

.weight-table td:last-child {
  font-weight: bold;
  color: #102a43;
}

.strategy-box,
.answer-box,
.formula-box {
  background: #fffdf8;
  border-left: 5px solid #d4af37;
  padding: 18px;
  border-radius: 8px;
  margin: 18px 0;
  color: #3e4c59;
}

.exercise-list {
  margin-left: 22px;
  margin-top: 15px;
}

.exercise-list li {
  margin-bottom: 14px;
}

details {
  margin-top: 18px;
  background: #f7f3eb;
  padding: 18px;
  border-radius: 8px;
  border: 1px solid #e5dccb;
}

summary {
  cursor: pointer;
  font-weight: bold;
  color: #102a43;
}

.nav-buttons {
  text-align: center;
}

.button {
  display: inline-block;
  background: #d4af37;
  color: #102a43;
  padding: 13px 24px;
  border-radius: 4px;
  text-decoration: none;
  font-weight: bold;
  margin: 6px;
}

.button:hover {
  background: #c19a2e;
}

footer {
  background: #102a43;
  color: #e5e7eb;
  text-align: center;
  padding: 24px;
  font-size: 14px;
}

@media (max-width: 800px) {
  .navbar {
    flex-direction: column;
    gap: 18px;
  }

  .nav-links {
    justify-content: center;
  }

  .page-header h1 {
    font-size: 34px;
  }

  .card {
    padding: 26px;
  }
}