I am still working on this!
Life events and such get in the way, and I've decided to rewrite the codebase in Rust using the atsamd-hal package for Rust embedded, for fun and to avoid the mess of arduino package dependencies.

As a part of this, the code has been rewritten to be entirely stack allocated and uses the hf2 protocol for updating and uploading assets, with the goal of a new hf2 bootloader that will display update progress.

The use of hf2 instead of simulated flash storage solves a lot of the compatibility issues I was having between mac/linux/windows.

In general the sdk setup and build process is a lot simpler now, especially for the web build which uses wasm-pack instead of emscripten. 

Feature parity between the two code bases is nearly present (only missing support for musical sequences), and I've moved on to making sprite assets again. The random reboots every couple days that were observed in the old code base have also ceased, though I never discovered the source.