Initially, the project, which first caused online head-scratching in 2021, was just about getting the rats to run down an online corridor. But now, neuroengineer Viktor Tóth has reached stage two, with far more ambitious hardware.

Originally, the rats stood in a harness on a freely rotating ball, with forward movement mapped to a simplified Doom II corridor and rewards dispensed as sweetened water. It worked after a fashion, but interaction was limited, and the “playing Doom” claim was always doing a lot of heavy lifting.

The new setup changes that by expanding movement and input. The rats still walk on a spherical treadmill, but now see the virtual world through a curved wraparound AMOLED screen that fills much more of their field of view.

Spatial feedback has been upgraded. Instead of relying purely on trial and error, the rig delivers gentle puffs of air to the rat’s snout when it collides with a wall, providing a clear physical cue without invasive techniques.

Crucially, the rats can now shoot. A physical trigger mechanism lets them activate Doom’s fire command, meaning they can perform multiple distinct in-game actions rather than wander corridors.

None of this involves neural implants or sci-fi brain jacks. The system relies entirely on external sensors, motion tracking and reward-based learning, with physical movement translated into standard Doom inputs.

That choice keeps the project firmly in open-source, hacker-friendly territory rather than locked inside a bespoke laboratory box.

Tóth has been clear that this is not about rats' understanding level design or demon behaviour. The animals are not planning routes or objectives; they are simply learning associations between movement, input, and reward within a virtual space.

What has changed is that the hardware is no longer the bottleneck. The platform can now support richer interactions, leaving training time and experimental design as the real constraints.

The result is something that has moved well beyond a one-off novelty. Doom’s ancient but flexible engine provides a cheap, well-understood 3D environment that can be bent to experimental needs without reinventing everything from scratch.

Of course, it is all fun and games until one of the rats escapes and gets its paws on a chainsaw.