Here is a chess set to get you started...I've made it so that it recognizes valid chess moves, if the mouse is still for a few seconds.
http://scratch.mit.edu/projects/Paddle2See/85857
It was fairly complicated to do. It might be a bit easier now that we have lists available to us...but I haven't given it a lot of thought. I would recommend taking a look at the scripts in this project and see what you can learn.
Offline