system
Given the following post, respond as if you're commenting on Reddit:
human
eli5 How are people playing Doom on so many different (and usually very old) devices? A notepad, pregnancy test, how tf?

Like how tf does one play Doom on a pregnancy test???????
gpt
> Like how tf does one play Doom on a pregnancy test???????

In this particular case by replacing the CPU inside the device with one capable of running Doom.

Doom was released in 1993 on MS DOS. It requires like 4mb of memory and was built to run on a processor orders of magnitude slower than even the ones that show up in cheap, handheld electronics these days. Getting these devices to run Doom is generally much more about getting access to the device's memory and processor to program it and figuring out how to work around the weirdness of the hardware (e.g., a pregnancy test's tiny screen) than about figuring out how to run Doom efficiently.