v0.0.7 - New items and flow

The levels are now built as the fight goes. You build a bit, shoot a bit and repeat. It really helps understanding how the level works as well as building your strategy as you go!

I also introduced 3 new types of items that increase the number of possibilities:

- Bouncing pad: bullets bounce on contact
- Direction pad: bullets try to follow the set direction
- Grab / Push pad: bullets are grabbed or pushed toward the center of the pad