Avoid hearts and the Queen of Spades
Hearts is a four-player trick-taking game, and here you sit at the bottom of the table against three AI opponents — West, North and East — each playing for themselves. The full 52-card deck is dealt, 13 cards each, and there is no passing phase: you play the hand you are dealt. Whoever holds the 2♣ must lead it to the first trick. Everyone must follow the suit that was led if they can; if not, they may play any card, except that nobody may throw a heart or the Queen of Spades on the first trick unless they hold nothing else. The highest card of the led suit wins the trick, and its winner leads the next one. Cards you aren't allowed to play are dimmed in your hand.
The aim is to take as few points as possible. Every heart you win in a trick costs 1 point and the Queen of Spades costs 13, for 26 points in each hand. Hearts can't be led until one has been thrown onto an earlier trick (or the leader holds nothing but hearts). If one player captures all 26 points they shoot the moon: they score nothing and each opponent takes 26 instead. Scores carry over from hand to hand and a new hand is dealt after each one. When someone reaches 100 the player with the lowest total wins; if two players share the lowest total, another hand is played.
You play Hearts here at a four-seat table against three independent AI opponents, so there are no partners and no alliances: every trick you dodge lands on somebody else. The rules are the standard ones without the passing phase. The 2 of clubs opens the hand, nobody may throw points on that first trick unless they have nothing else, you must follow suit when you can, hearts stay unleadable until one has been discarded, each heart costs a point and the Queen of Spades costs thirteen. Scores carry over from hand to hand until someone reaches 100, and the lowest total wins; a tie for lowest means one more hand. Cards you cannot legally play are dimmed, and the scoreboard beside each seat shows that player's running total plus the points they have taken in the current hand.
The opponents never see your cards or each other's. On Medium each one follows a clear set of priorities: when it can follow suit it ducks under the current winner with its lowest card, and only plays high when it has nothing lower; when it is void it gets rid of the Queen of Spades first, then its highest heart; and when it leads it picks its highest card that is not a heart or the Queen. Knowing that, you can predict a surprising amount: a Medium AI that leads the ace of spades is offering you the perfect place to drop the Queen. Hard also remembers every card played in the hand and which players have shown out of a suit, and plays accordingly.
Easy plays a random legal card every time, so it wins tricks it should avoid and often throws points on itself. Medium uses the priority rules described above: duck when possible, dump the Queen and high hearts when void, and lead high non-point cards. Hard ducks with its highest safe card, cashes high cards only while a suit is still safe, leads low spades to flush out the Queen, steers clear of suits an opponent is void in, unloads the Queen and stray high spades when void, and will take a heart itself to stop a moon shot. In simulated games at a mixed table, Hard seats took less than half as many points per hand as Medium seats. AI Training still cannot see anyone's cards: before each play it deals the unseen cards out many different ways that fit the voids it has seen, plays each deal to the end of the hand with Hard's rules for every seat, and chooses the card with the lowest average cost, moon shots included, spending up to about 0.4 seconds per card. At a table of two Training and two Hard seats, Training seats took about 5.8 points per hand to Hard's 9.0 and finished lowest in 13 of 16 games.
For the complete rules, the deeper strategy and the history of the game, read the full Hearts guide, or browse guides for all 33 games.