This one is recursive-grid for Hammerspoon users on macOS, and is probably the easiest of the open source implementations to fully customize. (I made it years ago)
I researched many different varint encodings for a GraphQL-specific binary format (resulting in Argo: https://github.com/msolomon/argo ). I ended up choosing protobuf-style zig-zag varints, but I also found these interesting:
For MacOS users of Hammerspoon, I made a similar plugin based on devoting the screen into successively smaller 3x3 grids: https://github.com/msolomon/griddle
If anyone is looking for a much cheaper alternative to this very impressive device for the sole purpose of typing or writing in daylight, I made a mobile app you can use in conjunction with a Kindle or other e-reader: https://solarwriter.msol.io
I would buy the RM2 in a heartbeat if it supported a keyboard over usb or Bluetooth.
Having an outdoor-friendly typewriter where text is saved seamlessly would be awesome for focused writing. I did my best to make it easy on a phone+keyboard+kindle (with SolarWriter https://msolomon.github.io/solarwriter-website/ ), but the Remarkable is so so close to the ideal experience—it just needs keyboard support.
I recently released an audio-based choose-your-own-adventure inspired game for playing in the car called Road Trip Adventures. If 7th Continent appeals to you then you should check it out!
I also use this daily, and have the same problem. I suppose this speaks to the weakness others have expressed (in using a premade configuration setup vs. slowly rolling your own), but I have otherwise found spf13-vim very useful.
This one is recursive-grid for Hammerspoon users on macOS, and is probably the easiest of the open source implementations to fully customize. (I made it years ago)