If you decrease this acceleration too much, what happens is that your cursor will end up moving in the opposite direction than your hand. However, if you experience (like me) for some reason strong accelerations when you move suddenly your mouse, for instance when you want to rocket jump, and or when you want to reach an enemy at the corner of your screen, then I suggest you to set x equal to a negative value. It is obviously your mouse sensitivity, replace x by what you want. I highly recommend to use 1, but some people prefer -1, so pick the one you prefer. 1 corresponds to di/raw mouse, while -1 is win32 mouse. \in_mouse x where x may be equal to either 1 or -1. However, I struggled a lot against Quake 3 to find a satisfying configuration. Having a good mouse configuration is essential in any fps game.
