Ok, so I've got the 'Thumby' version of Mazogs running in the top-left quarter of an Arduboy now, lol. It's tiny but playable... (as I understand it, it will shrink another 25% when transferred to a Thumby 0.42 inch screen though, woah).
Anyway, porting to Thumby now should just involve switching the SPI calls to I2C, updating the port numbers and probably using a different random generator, but apart from that it should 'just work' in theory.... I'll attempt it, but only once a) there's some Arduino IDE demo code for Thumby out there (hello world style with button reads) , or b) I've got a thumby. (early bird).