Nice port! Feels pretty authentic and the enemy animations look very good, just the explosion-animation of enemies could be improved, I think. Sound effects are a bit annoying, but old school ;-)
I had a bug: one of the big green enemies on the top was drawn only half (left or right half was missing). I didn't think about taking a screenshot, sorry.
Thanks! No problem, I'm aware of that one, and there should be code in there to stop it happening but obviously that's not working! Explosions are smaller than the arcade, I didn't want them to take up more space than the enemy that was destroyed as it would lead to more problems with the enemies next to it, like the one you saw.