Consumer surplus and cinema popcorn

What has cinema popcorn got to do with consumer surplus? Read this interesting article on how cinema operators try to capture your consumer surplus by selling you expensive popcorn:
http://www.tutor2u.net/blog/index.php/economics/comments/popcorn-and-price-discrimination/

This is linked to the topic of Price Discrimination which we'll learn later in the year when we study the monopoly.