Before designing anything new, we bought a dozen original players off eBay and took them apart, one at a time. Different makers, different production runs, some barely used and some clearly loved to pieces. Comparing them side by side was the fastest way to see what was actually consistent about the format and what varied maker to maker.
Reverse-engineering the geometry meant measuring everything: cartridge dimensions, gate tolerances, how much play the original mechanisms allowed before a loop started skipping. Dissecting a few down to their individual parts showed exactly how the film path, the gripper, and the optics all had to work together, which ended up shaping almost every decision that came after it.