it's DirectX directly
and this "big amount" is maybe 2 or 3 days of work until i can show you something which looks a lot more awesome than this

I can't use Gamestudio here because it's only a singleton (so one instance per program) which means you could edit only one level at a time (which makes sense in a way but would fuck up the whole management if you open another level)

XNA wont work either because of XNB and the Content Pipeline.

And i found no other C# Rendering Engine which fits my needs of lightweight and efficient coding