Make a shape class

[MunWolf]

As said above make a shape class that holds all our positional data, make it do our collision checking, and hold our vertices and geometrical data.

Make all the entities use that class as their geometry thingy so we can generalize our geometry.

[JonathanHHenson]

Done, but I decided not to make all entities use Shape object, since the bullet entity has no reason to have a shape