That's strange since I just tested the current itch version in Wine (Windows emulation in Linux) and it starts up without any problems. I will try to test it on a real Windows 11 machine at some point. I assume there is no way you can get a more detailed error message than the "Assertion failed!" window (Retry does nothing, right?) but otherwise let me know. Since I am currently converting the game to Rust, the error will hopefully not be present in the next version I upload but it will take quite a while before it is ready.