This is more a tech demo than a game, really, since there's no goal and you can just walk around the level and do.. well, nothing. That doesn't mean it's not cool, though. Canvex is a textured raycasting demo similar to Canvascape, but a bit more advanced. Where Canvascape was limited to walls aligned on an evenly spaced grid, Canvex has rooms of different shapes and different levels of elevation. This one also runs a lot better for me.

The game is dressed in Doom textures and there are even a few barrels and an animated Doom guy sprite thrown in for fun. Pretty cool, I say.

If you are interested in the technical details, Philip Taylor also made a page just for that.