More Destroy-able, more fun.

[arayul]

Too few enemies can be destroyed in the current version.
In particular, most enemies on the ground either repel bullets (cannons, tanks) or aren't hit by bullets in the first place (gas mines, deadly roombas, slime buckets, etc).

I want a reason to shoot more bullets to make this game more exciting

[luetage]

@arayul Being able to shoot everything down would make the game too easy in its current form.