Stackless coroutines for gamedev in ~200 lines of C++ (vittorioromeo.com)

Unrelated but Vittorio Romeo is the original developer behind OpenHexagon [0] which they call a "SuperHexagon clone" even though its way more than that.. It's a really fun game but its quite demanding

[0] : https://github.com/vittorioromeo/SSVOpenHexagon

I find the state machine example to be more readable and easier to reason about.