Well hello there, come to play the famous Diamond Game?
The rules are notoriously simple. Here's an ace of diamonds card (it's larger than normal), and here are a pile of pennies. We each take turns to place pennies on the card. Whoever is first not to be able to fit a penny onto the card loses.
Tell you what, you go first this time. Put a tenner on it. If you win, you'll get twenty!
How can the player guarantee that they win every time, regardless of how the barkeep plays?
For the purposes of the game, assume that both players are able to exactly follow any rule or process, regardless of its complexity.