I’m planning to use my 2D framework (built on xna 4.0) for my LD22 entry, so here it is: http://www.dynamicarcade.co.uk/downloads/xna/Dynamic2D/Dynamic2D.zip
It’s very bare bones, but it basically works like this:
Derive from Game for your game, which is just like xna’s Game but with a few more features. The only real difference is game logic should go in UpdateGame() instead of Update(), and try to Draw using GameObjects instead of overriding Draw().
Derive from GameObject for all of your game objects.
Derive from GameObjectBase for object templates. Set GameObjectType and use ConstructInstance() on the template to create an instance of a game object from that template. Then set the object’s initial properties (like position) then call AddToGame().