Yup I have his books and am old enough to have been around for all these games back in the day although I didn’t start modding games until Duke3D and Quake. I was actually poking around in the source of Doom the other day to see how it handled vector normalization in fixed point (answer convert the vector to direction vector then to angles then back to a length one vector by virtue of the conversion). It’s very fun to go back and pootle through.