Mmeh.
It was all right, I guess. But still, there has to be a way to make this game useful, like maybe adding Alpha toggling and the ability to share/save it. The crosshairs were a bad idea, and could've been replaced by circles showing where your stroke ends up. An undo button would help, too.
It's what pretty much what everybody wants in illustration software, so by the time this is perfect, it might as well be Adobe Illustrator on the Web.
2/5, I appreciate the idea, but there should be other kinds of games to make.