Made a bunch of changes, though few are actually evident while playing the game. Moved a lot of stuff out of the player and collidable test class to a MobileEntity class. Also changed collidable to be an interface and added a Hit method. Removed the quadtree we were using in the draw manager, replacing it with a list, and removed the property to get the sprite bounding box from drawable (it's not needed without a quadtree). I also added a really basic attack system to player. It could use a lot of fleshing out and tweaking, but it shows that you can hit things and they'll respond.