Nah it shouldn't, at least not how it's written at the moment ;) Have a look at your kill method - you might be resetting it, but you're also spawning as many enemies as you're removing. Only one line that's in the loop should actually be in a loop, take the other two outside of it and it works.

Very nice menus! What do the strange blocks / lines on the different maps do? At the moment they just seem to prevent me getting past for ages...

Hmm so it does! My only quick thought behind it is that the sequencer stop() method might reset the instrument used to some default value - but it doesn't seem that logical.

Well you could - but if you only need bullets to shoot left or right then I'd call that overkill! Unless you want the bullet's doing fairly complicated things then personally that's not how I'd implement it.

One of your images appears to have a forward slash in the file name and there's several images that start with a ? - that seems to be what windows doesn't like.

Silly point, but have you named files the same (case insensitively speaking?) On closer inspection winrar complains about overwriting files in the same directory its extracting to - so there may be something like a file.txt and File.txt in the same directory.

...or alternatively if that's not what you want, then you'll have to be a bit more specific on what you're trying to achieve!