Your circle 'filling' doesn't fill the entire cirlce (as you probably already have seen ;) ). To fix this you can: a) keep track of all the drawn points and draw a line towards that b) look at my fast graphics scenario and see how I did it there

To make it even faster, what you could do is what all games of today do: draw on a smaller image and scale that up. Maybe the result is very bad, but you can always try and not post it if it's bad :)