.fireworks-container {
  position: fixed;
  left: 0;
  top: 0;
  width: 100%;
  height: 100%;
  z-index: -1000;
  transition: 5s ;
  background-size: cover; 
  background-position: 50% 50%; 
  background-repeat: no-repeat; 
  background: #FFF; 
  opacity: 1;
}