Back when I did the Z80 based 'cosmic' games I planned to complete the set with Cosmic Guerilla.
This was a bit more work that I expected as the TMS9900 is not exactly a drop in replacement for the Z80.
Different memory access signals, ports are accessed using something called a CRU which I'd never heard about and doesn't even use the data bus.
Needs a little cleanup before checking in to ensure everything works and most of the random debug code is removed, but hopefully be added to the repository by next week.
n.b. real board uses a TMS9980, which is basically a TMS9900 with 8 bit bus