Ah, right. The version of nimgame2 you currently have is either not from the devel branch, or it was from the devel branch but is now too old.
Just run `nimble install nimgame2@#devel` to fix that. You'll also need to update sdl2_nim or else you'll run into [this issue](https://github.com/Vladar4/nimgame2/issues/38), so also run `nimble install sdl2_nim@#head`. I should amend the README to give some hints about that. For reference, these commits should work: * nimgame2: 5945db7a918d50ee98dfd51d77625959ed2ce742 * sdl2_nim: 90336b89649206c039dc9c8402385f70cef6f14c
