Two of the ways in which you can show an illusion of a button being pressed are: darkening the background-color and nudging its vertical position.

See the Pen Press Time by Brian Dys Sahagun (@briandys) on CodePen.

It is important to provide for a hint when a user activates an element in your user interface (in this example, a button). The feedback assures the user that the element “responds” to his action.

The advantage of using transform: translateY is that it does not affect the elements around it (unlike using margin or padding).