Hi!
That's very odd, i haven't had any crashing here. I wonder if some bug has slipped in the build that i uploaded, hmmm :o(
Thanks for the heads up anyway, I assume you mean you cant build other structures apart from walls/floors, as you did manage to build a mining unit, yes?
Will take a look, and see if i can get a new version uploaded with some bug fixes! Yes not much there at the moment, but hopefully with a few extra items to mess about with, may get to the start of a game prototype.