All sorted now. Thanks for your time. :-)
I am reviewing this game. However, I have had some difficulties on the Boss level. Mainly, that it doesn't appear to be progressing. On one occasion the Bosses spaceship did appear despite flying around the planet for and destroying the enemies for quite some time, on the other, his ship did appear but was not able to be destroyed. As far as I can see, it appears to be related to a bug where the UFO flies off the screen. Is this known to break the boss fight? Or am I just doing something wrong?
Aside from this problem, I have been thoroughly enjoying the game.