Hearts

Goal

Everyone plays for themselves. Each heart taken is worth 1 point and the queen of spades is worth 13 points. Points are bad: the game ends when a player reaches the limit (100 points by default) and the player with the fewest points wins.

Passing

After 13 cards are dealt to each player, three cards are passed: to the left on the first hand, to the right on the second, across on the third, then no passing on the fourth, and the cycle starts again.

How a hand is played

• The player holding the 2 of clubs leads it on the first trick.
• You must follow suit if you can; otherwise you may play any card (a discard).
• The highest card of the suit led wins the trick (the ace is highest); the winner leads the next trick.
• On the first trick, you cannot play a heart or the queen of spades unless you have no choice.
• You cannot lead a heart until hearts are broken (a heart has already been played), unless you only have hearts left.

Shooting the moon

A player who takes all the hearts and the queen of spades in a single hand “shoots the moon”: they score 0 points and each of the other three players receives 26 points.

About the AI

Levels 1 to 3 play by increasingly refined rules of thumb (discarding, hunting the queen, guarding against the moon). Levels 4 and 5 use Monte Carlo determinization: the AI generates thousands of possible distributions of the hidden cards, consistent with what it has seen (cards played, voids revealed by discards, cards it passed itself), plays each deal through to the end and picks the card that costs the fewest points on average. The AI never sees your cards.