Mouse Stuck at Top-Left Screen Corner

[Som1Lse]

The way I fixed this was, I downloaded ShiftWindow.
Then set up a rule for Amnesia to run in somewhat fullscreen. (Actually just position the window the border is outside the view and make it fit the screen. Trial and error simply)

The only downside of this is that you need to run ShiftWindow when you want to play Amnesia, but it isn't much of a problem. (can't give you any screenshots, I'm on Linux ATM)