Algodoo

Cool I learned something out of this!
10/10

When the downloads reaches 15, I'll add an Auto-Turret.

Ok, the tank with turret is uploaded.

The tracer's fade time is zero seconds...
EDIT: Nevermind...

Well, by looking at the script of all the objects, it is "supposed" to work, but a few variables are not declared, and it also uses lasers, which phun replaces with tracers. Also, you have to shake the buttons around alot for it to do anything. But, the point is it doesn't work.

You could add some thyme to that, and fix the bug.
Use conditional scripting.
In this case, make the paint ball immortal.

(e)=>{
e.other.immortal ? {} : {
(scene.addpen)({
pos := e.pos;
fadetime := 0.1;
color := [0.96, 0.829, 0.0, 1.0];
size := 0.2
})
}
}

That should prevent the paint ball from hitting itself
EDIT: Why didn't that work... If only there was a kill tracer option...