Logic gates go back a long way in Quake, starting with metlslime’s tutorial for Quake 2 all the way back in 1998. I first came across them on qmap, the now lost predecessor of func_msgboard. In 2013 I wrote a tutorial on this blog on how to create a logic gate using entity hacks, to take some of the computer-made-from-dominoes out of them. Then in 2016 I edited that post to fix some bugs, and it turns out the fix I wrote was over-complex in some ways, and still deficient in other circumstances.
Given that, I’ve decided to write up my latest design for logic gates in a stand-alone article. Apart from providing a single place for new readers to get the design from, I hope that the simplification in the new method and the extra features it offers will be helpful for everyone.