Like the [create search.gif] or the TypeWriter, the shopping cart is a little window that floats on top of other things. Once open, one can add as many items to the cart as desired. It all works very fluently as no communication with the server is necessary, it all happens on the client side, just like in real applications.
On checkout, a new window is opened in which the credit card verification and checkout is handled by www.saferpay.com.