worked on a veeeeery old project.. my "Keeper of the Dungeons"..
i managed to create the whole map out of terrains (still buggy.. >> see <<) But with a great FPS boost (500+ FPS *__*)
And my second success.. Destroy blocks of the terrains.
Leftclick sets a marker (the hazard stripe thing). this marker kills Health of a (pseudo) block - wich is a struct object. When health is low enough, the block will be destroyed (vertex movement) and the marker erased.
Next step is: moving the vertex, so the walls have multiple faces too, to create waving or rocky shapes.