Portal 2 Computability

This post is a part of my blog paleontology series. I dug up and restored this post on 2025-08-11. I made corrections to a number of spelling mistakes.

This was a neat find. I did not remember publishing this into the Steam Workshop. Also "computability" feels like a weird term for describing this.

The Portal 2 map editor was released today and I was wondering how it could be used as a sandbox for computability like Minecraft is. I have an example map in the workshop . I'm just going to copy-paste the explanation I gave there:

When I opened the editor my first thought was to build something crazy with the gels. I promptly became bored with the idea. However innovation never rests! My second instinct was to see if Portal 2 could be used to build basic logic gates and to consider the game in terms of computability.

When you enter, to the left is and AND gate followed by an OR gate (I cheated somewhat and used AND and NOT to create OR rather than synthesis a unique approach). To you right is a NOT gate followed by a clock.

I've been able to make similar gates using mechanical components, but I prefer the "solid state" nature of the lasers.

The nice part about constructing these is that (1) inputs and outputs can be connected in a many-to-many relationship and (2) outputs can be set to on or off initially (with a signal toggling them). So AND is simply two input piped into one output; it won't fire if they are not both on. NOT is piping an input into an output with the output on initially. OR I synthesised from the fact that a OR b <-> NOT(NOT(a) AND NOT(b)).

I choose to use block buttons for inputs and lasers for outputs, but the choice is arbitrary. Any of the inputs and outputs should work.

Thoughts comments suggestions? I posted this same brain dump on reddit if thats your cup of tea.