The camera is now centered with respect to the player. Updated the quadtree for collision to use the dimensions of the map - it's a bit hacky right now, the order of loading content has to be too specific for my tastes, but at least the entire map can be explored now. The bug where the player vibrates on the end of the map (that causes the exception on the top and left) persists, though. Hopefully that will go away when we have a border for the map.