How to change opacity of button when onmousedown universally,which my button has its own css class?

Ionic Framework ionic-v3
1

I want my button has simple animation when mouse down (e.g.:change opacity when click), but my button has its own css class:

.bottomButton{
  background-color:#e09f11;
  width:90%;
  height:80%;
  border-radius:0px;
  color:white;
}

and my button

<button ion-button clear (click)="shareButtonClicked()">Share</button>

I found my button has not animations when mouse is down (different from default

<button ion-button>Share</button>

)

is there any method to add mouse down animation (e.g.:mouse down) on all buttons in the app?