Peggle is such a wonderful game. Actually, it's the reason why my iPod's battery is almost depleted. I just spent a good few minutes reading a "behind the scenes" or "postmortem" of this game, created by PopCap. It's written in plain English, but it provides a very good look at how the game was made. It includes sketches, as well as videos with interviews and images of early prototypes. A must read for anybody interested in how a great game is designed. Here's the link. Notice that you need to subscribe to the newsletter before reading it. Just us a phony email; it works. Trust me, it's worth the pain.