Took a look into the source code of Apple’s home-made chess program and wasn’t disappointed from ProgrammerHumor

blikakisthepro
What are they doing? Did they make the ai unable to en pessant?

Szetyi
It’s slowing down response. So basically after you make your move, the computer already has it’s next move figured out in a few miliseonds, but if it actually moves instantly, the user unconsciously thinks it was too fast to be good. So the program delays it for a second, making it look like the computer has to think hard to beat you.

Same principle applies to all kinds of ui design. If your credit card for example gets accepted in a blink you get suspicious even when it’s fine.

Fugglymuffin
“Your flesh is a relic, a mere vessel” – the chess game