invadersI have to admit I prefer playing the mouse controlled version of this game above. Certainly less tiring on your arm. But its interesting as an experiment in alternative interaction methods. I've tried to callibrate the system for a webcam a small distance above the viewing surface but without knowing the exact geometry of webcam, user position (or even how large the light they are using is) and view screen its difficult to precisely correlate the user's motion to what happens on the screen. This is ok when you have hold of the object and have instant feedback but trying to throw an object can be difficult. One way to get around this would be to have the user move the object around in front of them and then click to fire. A controller like the one Sony was demonstrating at E3 would allow this. It will be interesting to see how developers adapt to these new 3D input systems being showcased.