For those who don't know, the Disk II Controller Card is considered by some to be the invention that best demonstrates Woz's genius.

It's also a great early example of the massive win you can get by replacing hardware with software (and "software" -- in the form of a state transition table encoded in a small ROM).

It's also one of the reasons there were so many fascinating and weird copy protections for Apple II software: since so much of the behavior was in software on the computer, it was malleable. (Since it uses the CPU for tight timing loops, the Apple II couldn't really do much else while using the disk.) The write-ups by 4am on IA are fun reading if you're into this kind of thing: https://archive.org/details/apple_ii_library_4am

There are some fun projects to record disks at the level of magnetic flux transitions. I'm mostly familiar with https://applesaucefdc.com by the amazing John Keoni Morris, which came with a new file format too, and some lovely UI software.