When starting the game if you switch to another window before the game loads it just assumes it has focus upon load and takes inputs from the keyboard. Like arrow presses. (Didn't test mouse but it might also have that issue.) I've seen a similar but not the same thing in another Unity based game. (Fortresscraft Evolved) I'm unsure if it can be handled or not without something changing on Unity's end. If you can't reproduce it, it might be related to me using Windows 7.