How to Shoot the Moon in Hearts: When It Pays, Tested

To shoot the moon in Hearts, you have to win all 13 hearts and the queen of spades in one hand; then you score 0 and everyone else scores 26. Go for it when your dealt hand counts 4 or more (1 for each ace and king, plus 1 more for each of the ace, king, queen and jack of hearts), pass your three lowest cards, and cash the cards nobody can beat. In our computer tests that rule won the most games against opponents who watch for a moon, but the better your opponents defend, the stronger the hand you need.

The strategy guide covers everyday Hearts play, and how to play Hearts has the full scoring rules. This guide goes deeper on the moon: which hands to try it with, how to play them, what a failed try costs, and how to stop someone else.

How we tested

Every number here comes from the computer players in Poozee's Hearts, with the same deck, rules and passing order. South went for the moon with a fixed plan (below) against three kinds of opponents:

• Medium, the game's Medium players. They never look out for a moon.
• Watchful Medium players, with one extra habit: once a player has 5 or more points and nobody else has any, they win tricks with points in them when they can, and stop throwing points onto that player's tricks.
• Hard, the game's strongest level, which plays out the rest of the hand in its head before every card.

We played whole games to see which rules win, and replayed single deals twice, once with South going for the moon and once playing normally, so the luck of the deal cancels out. Our opponents are computers, so the exact rates won't match your table, but the comparisons hold whenever everything else is equal.

What a moon hand looks like

First, the moons that happened without anyone trying. In 100,000 deals between four Medium players, someone took all 26 points 3,313 times. Here's what that player had been dealt, before the pass, next to all hands:

High cards make a moon, not lots of hearts. The shooters were dealt 2.9 aces and kings on average, against 2.0 for all hands, and fewer hearts: 2.8 hearts against 3.3. A long heart suit full of low cards loses tricks to the other players' high hearts, and one lost heart is enough to stop you.

When to go for it: count your high cards

Look at your 13 cards before you pass, and count:

1. 1 point for each ace and king, in any suit.
2. 1 more point for each of the ace, king, queen and jack of hearts. The ace and king of hearts end up worth 2 each.
3. With 4 or more, go for the moon. With less, play the hand normally.

A count of 4 or more came up in 36% of our deals. We tried eight rules for deciding, over 10,000 games each, against both Medium and watchful players. The table shows how often each rule says go, how often those attempts made the moon, and the share of games South won:

Against Medium, almost any attempt pays, because Medium players throw their high hearts onto whoever is winning the trick when they can't follow suit. Against watchful players, a count of 4 or more won the most games, with 3 or more aces and kings and a count of 3 close behind (gaps under a point are within the noise of 10,000 games). Five or more hearts was the clear failure: against watchful players it barely beat never trying. A long suit did better, but well short of the high-card rules.

Why it pays even though it usually fails

On the deals where the count was 4 or more, against watchful players, playing normally, you took 8.06 points and each opponent 6.27. Going for the moon, you took 10.25 and each opponent 11.61.

So by your own score alone, trying is a losing bet: failed attempts cost you 16.1 points on average, and since a moon saves you only the 8.06 points you'd have taken anyway, an attempt only breaks even if it works 50% of the time. Here it worked 36%. But every moon also adds 26 to each opponent's score, and Hearts is won by the lowest total, not by a low total. Against these opponents the 26s outweighed your extra points.

Pro tip: If the moon would push someone else past 100 while you're not the lowest, it ends the game, and the lowest total wins it, not you. Check the scores before you start.

How to play a moon hand

1. Pass your three lowest cards. Keep the aces, kings and high hearts that win tricks. With a count of 4 or more, our attempts made the moon 60% of the time against Medium players and 36% against watchful ones when South passed its lowest cards, over the same 100,000 deals (a quarter of them hold hands, with no pass). Passing the way Medium does (the queen and high spades when they're unprotected, then high hearts) made it only 25% and 11%.
2. Lead the cards nobody can beat. Count what's been played. Lead a card when no higher card of its suit is still out, hearts first once they're broken, so the other players have to follow suit with their hearts. With no sure card, lead the highest card of your longest suit.
3. Win every trick you can. When you follow suit, play your highest card, or your lowest winning card if you're the last to play. If you can't win the trick, play low and keep the queen.
4. Never throw away a heart or the queen. When you can't follow suit, throw your lowest other card. A heart you throw away is a heart someone else takes.
5. Give up the moment someone else takes a point. Go back to ducking tricks to keep your score down. The moon is gone either way.

One deal, two endings

Here's deal 55 of our test set, a hold hand with no passing. Your 13 cards are A♣ 3♦ 10♦ J♦ 4♠ 5♠ 7♠ J♠ K♠ A♠ 3♥ 7♥ K♥: four aces and kings, one of them the K♥, which counts twice, for a count of 5.

Against Medium, it works. You win the first trick with the A♣, the queen of spades falls under your K♠ on the second, and on the fifth West and East throw the 10♥ and A♥ onto your 5♠. You win all 13 tricks and every point.

Against Hard, the same plan wins the first nine tricks and the queen, but nobody throws you a heart. Hard keeps its hearts. That leaves you with the 3♦, 3♥, 7♥ and K♥, and since hearts haven't been broken, you have to lead the diamond. On trick 10 it goes You 3♦, West 8♥, North 9♦, East A♥: North wins it, and the moon is gone. You finished with 16 points (the queen and three hearts), North 6 and East 4.

Against strong defense

Hard stopped most attempts. Over the first 400 deals of our test set, 27 of 133 attempts with a count of 4 or more came off against Hard. Going for the moon on those deals, you took 15.9 points per hand instead of 10.7, and each opponent 6.9 instead of 5.5, so against Hard, trying cost more than it gained. Against players who defend this well, save the moon for hands that don't depend on anyone else's mistakes.

How to stop a moon

The watchful habit is a simple defense you can use yourself. Once one player has 5 or more points and nobody else has any:

1. If a trick has points in it and you can win it, win it.
2. When you can't follow suit, don't throw a heart or the queen onto a trick that player can still win. Throw it onto a trick they've already lost, or keep it.

It works against a real attempt. We gave the habit to West alone and had South go for the moon by the count rule: South's moons dropped from 62% to 54%, and West won 10.1% of games without the habit and 11.6% with it.

It has a price when nobody is really trying. In games where no one went for the moon on purpose, the habit cut moons by anyone from 3.3% of hands to 2.4%, yet West's win rate fell from 25.7% to 24.7%. Stopping a moon helps the other two players as much as you, and you're the one taking the points. (Deal by deal, a player with the habit took 6.81 points per hand instead of 6.87 over 20,000 deals, so the cost isn't in your average score.) Use it when a player has shown they go for the moon, not every time someone picks up the queen early.

Keep playing

• Play Hearts against three computer players, and try the count rule against Medium and Hard
• Hearts strategy: the everyday habits that lower your score, tested the same way
• Spades strategy, measured with the same kind of computer games