First: The editor and the clone game do not make use of the same code. When making the clone I copied all code and changed/added a lot of things. I want to change that

Next: The next version will be able to edit terrains / objects, add new lemming-styles etc. etc. Also higher resolution will be possible.
The "lemming framework" has to be rewritten to support old styles AND new ones.

Now you get me really confused. I know the Windows API is extremely slow, when it comes to drawing to the screen. So I was actually hoping the DirectX / OpenGL would eliminate this problem. Why won't the game be using hardware acceleration? (I'm an almost complete Noob to OpenGL and DirectX).

With the Graphics32 (TImage32) I use the "Dirty Pixels" scheme. Erase animations - process mechanics - Draw animations. That's why it has an acceptable speed.