This is the lean4 version of the classical Natural Number Game. It uses the Lean4 Game Engine and is running live at adam.math.hhu.de.

The game was initially designed for lean3 and has been adapted for lean4. See lean3 version.

Getting Started

You can develop the game as any lean project and use lake build to build it.

Moreover, there are multiple ways to run the game while developing it, which are described in Running Games Locally


PRs/Issues fixing typos, inconsistencies, missing hints, etc. are very welcome!


We happily accept translations of the game into different lanugages! You can use .i18n/en/Game.pot and translate it into .i18n/{lang}/Game.po where {lang} is the ISO language code like fr or en_UK, using for example POEdit.

We would like the following requirements for a translation PR:

  • One independent person from the community, who understands the language, gives a review on the PR. You could for example look at the Lean Community Map or ask on Zulip. Such a review can be quite generic and does not have to be super detailed.
  • In the credits (i.e. in the string translating them), ideally you should add yourself as a translator for this language.


See Creating a Game at the lean4game repo for a detailed explanation.