This is a great idea and well executed (particularly the hosting/finding games, it was really easy to find a player to test our "Mirror Matieness".
Couple of suggestions:
- an eraser would be swell (I was playing on a trackpad and it's hard to draw a straight line!)
- more feedback on our rating at every round (I'd love to see the % the algo came up with)
- when clicking in out of the window and back in, the paint brush is usually a couple of pixels off the mouse pointer