Low poly for speed of game development. The walls are single planes with a texture painted on it. I then joined the planes together to form a single mesh. (speed reasons). The floors and grounds are simple cubes. Some of them have been shaped a little bit.
I had the idea of using base meshes for the GFX in the game. I think it might still work, but need applied to a different genre. They can be texture painted and animated just like other models. The reason is, speed of developing the game itself, while having models that look good enough.
I'm now working on a new project with little more detailed models. Still keeping things simple, but I am spending much more time on it.