I love this whole thing. I think you could make it feel more like “racing” if you have to race against other factions to get the good scavenging loot. Maybe the city is only accessible at certain points, so you end up with giant mad max convoys racing each other into and through the city.

Saying an ISA is just a hardware API vastly oversimplifies what an architecture is. There is way more to it than just the instruction set, because you can’t have an instruction set without also defining the numbers and types of registers, the mapping of memory and how the CPU interacts with it, the input/output model for the system, and a bunch of other features like virtual memory, addressing modes etc. Just to give an idea, the ARM reference is 850 pages long.