This is an interesting project to build for the C64 and is a very cheap SD card interface. I'm also looking into seeing if it's possible to do something similar for other 8-bit systems as the motor handling is vital for some computers e.g. electron, BBC, and MSX. There are apps like Tapdancer for android that can play all cassette file types but without the motor handling they do not work very well so this could be perfect.
