The rules of Half Moon

Setup

The game uses 2 shuffled decks of 52 cards: 104 cards, with two copies of each. The app deals 96 of them into 12 piles of 8 cards; the remaining 8 form the reserve. There is no stock or foundation: everything is on the table from the start.

On screen, the piles form an arc open at the bottom: 3 piles on the left, 7 across the top and 2 on the right below the corner. The reserve sits in the centre of the arc, in two rows of four. The app shows only the top card of each pile: the next card appears when the top card is removed. The diagrams on this site follow this layout and add, below each card, the pile number (1 to 12) or reserve slot number (R1 to R8) and its card count.

Allowed removals

• The playable cards are the top card of each of the 12 piles and every card still in the reserve.
• Pair: two cards from Ace (worth 1) to 10 that add up to 11. There are five possible combinations: Ace and 10, 2 and 9, 3 and 8, 4 and 7, or 5 and 6. Suit does not matter.
• Triplet: a Jack, a Queen and a King, of any suits. Face cards never form a pair.
• You can combine cards from different sources: a pile card with a reserve card, two reserve cards, or two cards from piles.
• Removed cards leave the game; an emptied pile and an emptied reserve slot stay empty.

An example from the winning game on the Examples page: on the first move, the 5♠ from pile 1 and the 6♦ from pile 8 are removed together (5 + 6 = 11). Pile 8 then reveals a V♣, which is removed on the next move with the D♥ from pile 5 and the R♥ from pile 3.

Tapping the cards

• Tap a first card to select it. Tapping a second card that adds up to 11 with it removes the pair.
• For a triplet, tap the three face cards one after another; they are removed on the third tap. The app never chooses the third card for the player.
• Tapping the selected card again deselects it.
• If the second card does not fit, nothing is removed: two number cards that do not add up to 11 (the 5♠ and the A♥ from the same deal), or a number card and a face card (the 5♠ and the R♥), clear the selection. Two face cards of the same rank (two R♥) do not combine: the second becomes the selected card.
• With the “Move errors” setting, which is off by default, the app explains: “The sum must equal 11” or “Requires a Jack, a Queen and a King”.
• As soon as a card is selected, the “Placement assistance” setting dims cards that cannot be combined with it.

Scoring

Each pair adds 10 to the score, and each triplet 15. The score never falls below zero, and the timer does not affect it. Since the two decks contain 80 cards from Ace to 10 and 24 face cards, a winning game always removes 40 pairs and 8 triplets: 48 moves and a score of 520, no more and no less.

The end of the game

• Victory: all 104 cards have been removed.
• Dead end: among the playable cards, there is no pair adding up to 11 and no Jack, Queen, King trio. The app announces this; you can undo or start a new game.

What the app does

• Undo: up to the last 100 moves; the cards return to their places, and the score and move counter decrease.
• Status bar: time, score, moves and deal code.
• Game code: each deal has a code (such as HM1-N-AAAAAAB) that recreates it exactly.
• No solver or hint button: the app does not tell you whether a deal can be won.

The app's rules and tradition

Removing two cards that add up to 11 and face cards in sets of three is the rule of a family of solitaire games known in English as Elevens, usually played with a single deck in a square of nine cards. Half Moon applies this rule to two decks, with piles in an arc and a reserve that is always playable.