Thanks for the reply GeometriX, but my main issue, and I believe rekjl's original one as well, was not about the code logic, but rather about the actual sensor value readings
And probably most people indeed use the values for C2 games like you described, but this mechanism doesn't work for "absolute" orientation, because the numbers are not "proportional"
For example you can try yourself, if you lift the left side of your device to read Gamma 45, it's actually just around 30 degrees rotation (and then catch up fine at Gamma 90 / 90 degrees)
Like I mentioned before, this looks like ease-in ease-out, and I'm starting to wonder if C2 is applying that on purpose for more precision with the kind of gameplay mechanism you described
But then it breaks the option to make a simple compass, and I still invite anyone to make a working one using the Alpha value...