I'm working on Mutacortechs, an ALife simulation where "organisms" each have their own emulated 16-bit processor with 64K RAM. Like Core Wars for the 21st century. It's a small project compared to what some others here are working on, but it's an order of magnitude larger than anything this embedded EE has ever written. I have the ISA designed, assembler complete, emulator stage 1 complete (160/204 instructions implemented), and the start of the simulation working. Last night I wrote a program in custom assembly for an "organism" that looked around, found food, moved toward it, and ate it. I'm pretty excited by the milestone!