Lasers! I thought these would be fun to make, but honestly they were a bit of a pain. I like how they've turned out, though.
As you can see in the video, I haven't made lasers kill you yet, though I probably will. Also to be decided is what happens when a bullet hits a laser. I can think of three options that make sense: do nothing, vapourize it or have it bounce off. Once I've made a few levels a solution will probably present itself.
(And, as promised, I've made collectible items too. But those aren't as interesting.)