One of the games was a “hide the marble under one of three cups, follow the cup, then guess where it is” thing. On the highest difficulty it would give very high rewards but it was almost impossible to follow.

However, I used to play on a school computer that was ancient. It couldn’t play the flash animation at full speed, so I would watch it slowly move the cups around, easily follow, and get it right every time. When playing at home I would lose, but at school I nailed it.