Actually, the Lua Missions are excellent! I highly recommend taking the time to work through them. More than just a series of exercises (like most of the foo-koans), there's actually a narrative and a larger lesson you can learn if you work through the full problem set.

Hi, Lua Missions author here!

Thanks for the kind words. One word of warning though: I never got around to make one mission about coroutines.

But I accept pull requests :)