Why Quake 1 & 2 invoke mouse acceleration

I discovered that both Quake 1 & 2 invoke SystemParametersInfo in IN_ActivateMouse with the third variable being {0,0,1}. The 1 activates mouse acceleration. Quake 3 doesn't invoke SystemParametersInfo in IN_ActivateWin32Mouse, so it uses whatever you have set for mouse accel (what Microsoft calls 'enhanced pointer precision'.) Well you can morph the mouse acceleration curve into a linear response line by editing the registry such as the mouse-acceleration-fix by MarkC. So if an application activates mouse acceleration it will still be linear.

Envisioning various dimensions

2D beings
-we have 1D eyes, hence we can see 1D-sections of 2D, and can only 'envision' how all the 2D sections come-together as a whole
-we can see 1D worlds in their entirety (many 0D pixels stacked onto a 1D line) from the vantage point of another dimension (y axis)

3D beings
-we have 2D eyes, hence we can see 2D-sections of 3D, and can only 'envision' how all the 3D sections come-together as a whole
-we can see a single 2D world in its entirety (many 1D lines stacked onto a 2D plane) from the vantage point of another dimension (z axis)

4D beings
Difficult to envision as we are 3D beings. And I don't mean the 4D in the Back to the future since where the 4th dimension is time!