Thank you for that. I never actually learned how to do this as my own games, written as a kid, were way too small.

These days it is so much easier to have access to all kinds of technical information on the C64. I remember travelling half a day to the single bookshop that sold assembler books. Learning anything beyond those books was mostly a matter of figuring out other people's code (e.g. the 'sprites in the border' hack).