Someone clearly had a vision, decided to show us it, and then leave without further elaboration. Brainchild is part maze, part keyhunt, both of which are elevated by the level design. The brush and texture work is fairly basic, but there's a lot of attention to detail paid here in other aspects that I feel even the misaligned textures might be intentional. You'll never be lost for long, as the routing is strong, thanks in part to the stellar use of light and shadow, and the keys you gain open up connecting paths between different parts of the levels.

The level theme seems to be aiming for something futuristic (compounded by the heavily modified menu elements), though with Thief's default textures you can only do so much. The layout itself does a lot of the heavy lifting, creating a sense of scale that leaves you feeling like a rat stuck in the bowels of some unbeholdable machine.

This mission is basic in a lot of ways, but the deliberance of its presentation kept me wildly intrigued from start, to finish, and I dare say, a good while after this.

You left me intrigued from the start so I have done some research.
https://shadowofdoubtcampaign.wordpress.com/2013/03/02/preview-t2-brainchild/

Hey, thanks, this was an interesting little snippet to read!