Make-like build system. This would expose students to a few useful concepts, and can be a 'jumping-off point' into various more advanced concepts.

- topological sorting the build graph - what is a graph - running child processes - what a process is - process api - interaction with the filesystem - r/w files - mtime comparisons - how computers store time - what is incremental execution

I would suggest to skip parsing, and use a Python literal to hold the 'Makefile'-equivalent dependency graph data structure.

You let students come up with their own fun build graphs, like making sushi:

tuna_maki -> nori, cooked_rice, tuna_fillet, chef, sushi_roller

cooked_rice -> uncooked_rice, rice_cooker, water, rice_seasoning

tuna_fillet -> tuna_slab, knife

tuna_slab -> fishmonger, money

nori -> algae, dehydrator

And then, when executed, it would print the steps, or say that a target was already made.