body {
  font-family: "Segoe UI", Arial, sans-serif;
  background: #f5f7fa;
  margin: 0;
  padding: 0;
  color: #333;
}

.calendar {
  max-width: 1100px;
  margin: 0 auto;
  padding: 40px 20px;
}

.calendar h2 {
  text-align: center;
  font-size: 2rem;
  margin-bottom: 30px;
  color: #1a73e8;
}

.tabs {
  display: flex;
  justify-content: center;
  gap: 15px;
  margin-bottom: 25px;
}

.tab-btn {
  padding: 10px 20px;
  border: none;
  background: #e0e0e0;
  border-radius: 6px;
  cursor: pointer;
  transition: background 0.3s ease;
  font-size: 1rem;
}

.tab-btn.active {
  background: #1a73e8;
  color: #fff;
}

.tab-content {
  display: none;
}

.tab-content.active {
  display: block;
}

.material-card {
  background: #fff;
  border-radius: 10px;
  padding: 20px;
  margin-bottom: 15px;
  box-shadow: 0 4px 12px rgba(0,0,0,0.1);
}

.material-card h4 {
  margin-top: 0;
  color: #1a73e8;
}

.btn {
  display: inline-block;
  margin-top: 10px;
  padding: 8px 15px;
  background: #1a73e8;
  color: #fff;
  text-decoration: none;
  border-radius: 6px;
  transition: background 0.3s ease;
}

.btn:hover {
  background: #155ab6;
}