bootstrap4-buttons-extended is simple library for add more interactive styles to bootstrap 4 buttons
you have two versions the minifed and unminified version you can use any of them:
<link rel="stylesheet" type="text/css" href="path/to/your/buttons.css">
btn-3d
btn-icon-overlay
btn-circle
btn-fill
just put after btn-fill
class, the fill direction
btn-fill fill-right
btn-green
btn-blue
btn-purple
btn-orange
btn-dirty-green
btn-aqua
btn-grey
btn-facebook
btn-twitter
btn-pinterest
btn-youtube
btn-linkedin
btn-google-plus