system
Given the following post, respond as if you're commenting on Reddit:
human
Why doom is ported to every kind of machine?

I agree it's a great game at its time, but why ported it to almost anything has lcd screen and buttons.

Is there any reasons for that ?

And if i want to port Doom to some machines, where should i start first?

Many thanks.
gpt
The source is open and very portable while being small enough to feasibly port yet large enough to not be a trivial example.  It's a clear indication that you have basic framebuffer access and responsive I/O capabilities, the bare minimum for a system to be considered functional.

More importantly at this point it's tradition.  You can pick any sort of graphical application to demonstrate on a new platform but the one people will remember is the first to run Doom.