CODE EXAMPLE FOR CSS

transition css

div:hover {
  background-color: #000;
  transition: background-color 400ms;
}

/* Or control over animation with transition timing */
div:hover {
  background-color: #000;
  transition: background-color 400ms ease-in-out;
}

/* timing - linear|ease|ease-in|ease-out|ease-in-out|cubic-bezier(n,n,n,n) */