Canvas clip problems

[Daniel Zwolenski]

Here is one I can't reproduce in smaller code.

http://www.screencast.com/t/AJZjx1TjFT

You can see that when the enemies start off the canvas they end up leaving
a smear behind. When they leave the canvas at the other end they also
smear.

I suspect it's something to do with the clipping code used in the game but
I haven't been able to narrow it down (and this area I was a bit flaky on
and I think Richard did the starting setup for).

It's probably a case of clipping properly, but should this sort of
behaviour be even possible to occur?

p.s. thanks for the Camtasia tips - nice product.