You have an extra 8 bits in the PIA's I/O port direction register. If you're not using inputs right now you can use that as temporary memory. It's not like the joystick cares if it's getting a little backwards current.

Oh, there are lots of tricks. And when the tricks run out, you run on desperation, you rewrite your display kernel for the fifth time, to get 8 precious cycles back just before the score line. Victory is sweet.

I had a cow-orker (we were both out of the 8-bit computer games division) who decided it would be good for his career (at Atari) to learn 2600 game programming. He got a Stella devkit, a copy of the same dev documentation that has been published everywhere (that's all that anyone got at the time), and over the next four months or so I watched him slowly go mad. I'm not kidding, his mental state was terrible. About then Jack Tramiel bought the company and we all got to work on different stuff, yay.

The 2600 hackers over in Consumer games had a reputation for being pretty wild and unhinged. I am half serious when I say that it was the machine that did it to them.