How to display just notification if shopping cart is empty

Hi There,
I am quite fresh and have no huge experience with ecommerce but decided to try to build ecommerce website for my boyfriend.
I saw very nice effect at https://organico.splashingpixels.com/
If you have empty shopping cart only notification is displayed and user is not redirected to checkout page. Can somebody give me a clue how to do this?
Thanks in advance, Anita