A very good game indeed.
I think the reactor (I mean the tile in the Reactor level which says something, not completely sure whether it is required to win) was generated in an unreachable location in one of my games.
Also sometimes a keycard to the vault is generated in the escape pod room. Technically, you can eventually open the vault in this case, but in practice, no. So it seems like a weird special case for the graph-based generation algorithm...
