• Normal keypresses, mod taps, layers, chords, mouse keys
• Cirque trackpad support, with support for using it to scroll
• Some pretty neopixel animations (that sync between sides, and transition smoothly)
• Support for a st7789 display, using slint to render the UI
• Single firmware binary, everything works no matter which side is plugged in
• Double tapping the update button puts the mcu into dfu mode
• The device pretends to be a RP Pico and supports being put into DFU mode by picotool

You'll need cargo and picotool installed

• cargo build --release -Zbuild-std=core,alloc,panic_abort -Zbuild-std-features=panic_immediate_abort
  • It's fine to use just cargo build --release here, the extra parameters just make the binary a bit smaller.
• picotool load -f ./target/thumbv6m-none-eabi/release/boot
  • The bootloader only needs flashing the first time
• picotool load -f ./target/thumbv6m-none-eabi/release/binary
• picotool reboot

(You can use either the nix flake or install picotool yourself)

You can use https://github.com/simmsb/keylayout to generate key layouts (and also generate previes of them), check out the one I use