The awesomest puzzle game ever made. I used to have it on my old black-and-white mac. You solve various puzzles based upon the Tarot cards. See fools-errand.com for more details. You will not be disappointed, but you will lose a lot of sleep, as it's addictive.
The sequel to The Fool's Errand, A Fool and His Money, is coming out this April, seventeen years since the original. I hope the wait was worth it.