style.css

```css
/* Global animations */
.fade-in {
  animation: fadeIn 0.5s ease-in;
}

@keyframes fadeIn {
  from { opacity: 0; transform: translateY(20px); }
  to { opacity: 1; transform: translateY(0); }
}

/* Certificate card animation */
.certificate-card {
  transition: all 0.3s ease;
}

.certificate-card:hover {
  transform: translateY(-5px);
  box-shadow: 0 10px 20px rgba(0,0,0,0.1);
}

/* Button animations */
.btn-pulse {
  animation: pulse 2s infinite;
}

@keyframes pulse {
  0% { box-shadow: 0 0 0 0 rgba(74, 222, 128, 0.7); }
  70% { box-shadow: 0 0 0 10px rgba(74, 222, 128, 0); }
  100% { box-shadow: 0 0 0 0 rgba(74, 222, 128, 0); }
}

/* Loading spinner */
.spinner {
  animation: spin 1s linear infinite;
}

@keyframes spin {
  from { transform: rotate(0deg); }
  to { transform: rotate(360deg); }
}

/* Responsive layout adjustments */
@media (max-width: 768px) {
  .responsive-flex {
    flex-direction: column;
  }
}
```