zoom in when you draw your lines and they probably won't be as blocky. also try decreasing your mouse sensitivity. if you use winXP, click: start > control panel > printers and other hardware > mouse, then click on the "pointer options" tab and move the top slider to the left some.

between that and zooming in, you should be able to reduce mouse skipping. right now it seems like your mouse skips to every 6th pixel or so, which is terrible.

lol! this is cool, but youve already coulored it! X_X