https://bugs.winehq.org/show_bug.cgi?id=45713
--- Comment #4 from Stellarspace macariopatrick@icloud.com --- (In reply to Fabian Maurer from comment #2)
Ok, after downloading and installing webplayer from https://unity3d.com/de/webplayer, I get the same error. But this also seems to happen to windows users, can't test on windows right now.
The latest version of Unity Web Player does not work for FusionFall Retro. FusionFall Retro uses a custom version of Unity Web Player that is much older than the latest version.