Tank Boom

For this update, you can attack enemy units. Move your tanks down toward and onto the red tank, and it goes boom!

Combat is simple right now: the attacker always wins.

The long delay between releases was me reorganizing code. I separated the cursor into a new dedicated object, and added "turn" and "team" objects. The new battle feature is also in its own object. I'm sure I'll be refactoring more as the project grows.