Oh What Fun, might be the name of the paper packet used but it's also very apt for these interactive sliding pop-up cards.

I love how easy these window cards were to make.  During a 5 for 5 session (check out the events page for more info on that) a friend and I wanted to make something a little different. She spotted some window cards on Pinterest and we got creating. 
Using circle thin cuts for the windows and scalpel and metal ruler for precision cutting the cassette tape out and acetate for the window, we ended up making these cards cute cards.