You might wonder how small you can go still have an interactive and self-hosted computing system, or what happens when you don't have an internet connection for months. Uxn is one attempt to answer these questions. It is a computing stack developed by Rek Bella and Devine Lu Linvega (collectively Hundred Rabbits), who travel around the world on their sailboat. I haven't sailed in about 20 years, but I find these solarpunk perspectives interesting.

Uxn is stack-based processor, usually implemented as an emulator running on whatever hardware is available.
Uxntal is programming language, somewhere between Assembly and Forth.
Varvara is the set of peripherals usually attached to an Uxn processor.
I made my own, slightly different thing based on a Raspberry Pi Pico / RP2040.