I think to make a paint with GS is not really a good idea... It's a nice feature, if you can create pictures as flags for a team in a multiplayer-game as example. But your one, how hummel said, really sucks. If you want to create a good and working paint you have to add MANY more features, like connection between two points, a straight line, a possibility to save your work, etc. etc. etc.

Oh and the mouse-move is really uncomfortable.