Well, I've now added in an modified laser sound into my game (thanks chronozphere!), and there are also 3 kinds of asteroids now too:

Grey asteroids - large ones split into 2 smaller medium ones.
Gold asteroids - big bonus points (1000), but take much more energy and time to destroy.
Fire asteroids - bigger bonus points (1500), but take even more energy and time to destroy. Also if one of these hits the Earth, then you suffer 2x damage on the Earth damage bar.

I have uploaded the new version to the competition site...yay!

I would like to upgrade/add more stuff in the game, but I just don't have time - perhaps after the competition!

I haven't uploaded the new version to my website yet...

Good luck to all!!
cheers,
Paul