Hold down 1 to draw. Press 2 to erase everything. Hold down 3 and 1 to erase bits at a time. (Like using an eraser!) Hold down A and 1 to get a red colour. Hold down S and 1 to get a blue colour. Hold down D and 1 to get a green colour.
Thanks to ha90_ for the inspiration with his "Draw Random Stuff" project. P.S I will make a studio where you guys can post your drawings for everyone to see!