Changed level 2_4, and started working towards adding audio (Update #5)

Changed 2_4 to make the first half of the level more interesting (I've attached images of the old and new versions to this post). I'm not sure if I'll keep this change, since I'm worried it's a little too fiddly and doesn't really add much to the level. Feel free to tell me whether it's an improvement.

Also, I started working on the foundations to add audio to the game. There's still a lot I don't understand about creating audio, so it might be a while until I'm ready to actually add any sounds to game.