Note that this was created long before the recently posted article. So, its rules variations are totally correct, because it wasn't trying to match the article'

Note that this was created long before the recently posted article. So, its rules variations are totally correct, because it wasn't trying to match the article's definition of the game ;) It originally used what it calls Rule 5a, as the article proposed, but that allows the first player to always win (see Perfect), so it now uses Rule 5b by default, but it can be toggled easily. There are also a ton of other config options if you scroll down past the initial comments; most of the variants, like the Perfect one, just have different defaults for linking convenience.