pico-rectangle VS pico-os

Check out https://github.com/JulienBernard3383279/pico-rectangle

That you don't have to worry about that being the case. If you want to see the nitty gritty of how it functions, here is the pico rectangle ultimate DAC algorithm

My main concern is power. The rp2040+ supports simultaneous charging and use, but I also want to make sure I don't accidentally leak power back up the cable (especially to the gamecube, since this could break it). I followed the circuit diagram for the usb c breakout, but since I am using a battery pack I have some concerns. There is also the rp2040+ schematic available online.

if you're playing on console it's a different story, you'd have to either get a prebuilt that works on the gamecube or use something like pico-rectangle.

Pico Rectangle - Arte

It's easy enough to write your own firmware for a box controller, the software is already out there on Github. So it's not enough even if all of Hitbox, Hax, Goomy, Greg Turbo, and Panda are all on board.

any "Raspberry Pi" with 256 MB - is a perfect test machine.

https://en.wikipedia.org/wiki/Raspberry_Pi

And there is an extra minimal alternative:

Raspberry Pi Pico ( 264 KB; available from $4 + https://github.com/asynts/pico-os )

"Raspberry Pi Pico comes with Dual-Core ARM Cortex M0+ processor, which can run up to 133MHz. It has 264KB of SRAM and 2MB of on-board flash storage, but we can extend up to 16MB of off-chip Flash memory via a dedicated Quad-SPI bus."