Decades ago, I had more or less topped out playing Othello against my Apple ][e. A game could be completed in under ninety seconds, with my moves being as fast as that of the computer. I took photos (with actual film) of beating the machine long before the board could be filled, but I was getting stale, essentially training myself to fight against this deterministic opponent who couldn't have been all that bright, given the time. I began to make deliberately bad choices in the early game to see if I could recover, but even that wore out.
I eventually settled on POKEing parts of the memory where the game was held. Typically, this resulted in an un-runnable program, or the program would place pieces on the lines rather than between them, all sorts of oddball behavior. Every so often, though, I would get a working game that would play against me using the usual rules, but differently enough that it would throw me off.
It was primitive but amusing.