.heading1 {
  animation: slideIn 1s ease forwards;
}
.heading2 {
  animation: slideIn 1s ease forwards;
  animation-delay: 1.2s;  /* start after heading1 finishes */
}

@keyframes slideIn {
  from { transform: translateX(-100%); opacity: 0; }
  to { transform: translateX(0); opacity: 1; }
}