Day 6: Edging closer

I added several levels, fixed a few bugs and gnerally got closer to something submittable.

I added sound, although it sometimes doesn't play the desired effect. I'm not quite sure why, and I probably won't have time to figure that out before the deadline. I also added some configuration options, so you can enable and disable sound, and choose the starting level (which is mainly a debugging aid, but it's also the sort of feature that may be useful suring judging).

At some point in the last couple of days, I broke the game on android, so I fixed that. It's rather slow on my phone - I think I know what I've done wrong, although I may not have time to correct that before the deadline. It's also a bit painful to play using a touch interface, but I think I can improve that without too much effort.