Been doing tooling work to support Toxa's upgrade of ZGB to a cross-platform engine that adds MegaDuck, SMS and Game Gear support (to the existing GB/GBC capability).
It's mostly Makefile, build automation and converting utilities from python. Not particularly exciting or glamorous, but can be satisfying when the output of a converted utility matches the reference output without too much struggle. :)
@Jeltron No idea.
I think a dream of toxa's for GBStudio to support more consoles than GB/GBC. The GBStudio UI support would prob be hard though, and it's unclear if the UI folks would have the time/energy/interest for that kind of thing.
Same applies for Michel's dream of NES GBStudio that he's been gradually working toward for 2 years now.
In the mean time ZGB is a sort of middle ground. A smaller engine that requires more programming but now decently builds for SMS/GG. (not yet released)
Kojote
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Jeltron