/* ========= 响应式设计 ========= */
@media (max-width: 768px) {
  .navbar { flex-direction: column; padding: 10px 20px; }
  .nav-links { flex-direction: column; gap: 10px; text-align: center; }
  .nav-auth { flex-direction: column; gap: 10px; }
  .hero { padding: 100px 20px 60px; }
  .hero h1 { font-size: 28px; }
  .hero p { font-size: 16px; }
  .section { padding: 60px 20px; }
  .section-title { font-size: 28px; }
  .courses-grid, .team-grid, .news-grid { grid-template-columns: 1fr; }
  .about-content { grid-template-columns: 1fr; }
  .contact-form { width: 100%; }
  .footer-content { grid-template-columns: 1fr; gap: 30px; }
  .hero-buttons { flex-direction: column; align-items: center; }
  .about-stats { flex-direction: column; gap: 20px; }
}
@media (max-width: 480px) {
  .hero h1 { font-size: 22px; }
  .btn-hero { padding: 10px 20px; font-size: 14px; width: 100%; }
  .feature-card, .course-card, .team-card, .news-card { margin: 0 10px; }
}