Clean up "Hacked" CSS

There was no need to over complicate the 'hacked' CSS to use the
bounce.js library.

By simply hiding the div to begin, then showing it on mouse over you
will get the desired effect without the "jitter" that is a pain in the
video!

Timing, etc. can be adjusted as needed to get the desired effect, but this leaves the CSS far cleaner which is a definite plus! 
Display flex here as it was removed from original definition