Mancala — the free browser version of Kalah, against a computer

Twelve pits, four stones in each, and a store at either end. You scoop up a pit and drop its stones one by one round the board, and whatever ends up in your store at the end of the game is yours. That is the whole of Mancala — and it is enough to have kept people playing for thousands of years, because two small extras turn a counting exercise into a knife fight: land your last stone in your own store and you move again, and land it in an empty pit on your side and you capture everything facing it.

This is the version almost everyone means by "Mancala": Kalah, six pits a side, four stones a pit, 48 stones in play. You always move first. Your score is simply how many stones finish in your store, so 25 out of 48 is a win and anything above that is a rout. The computer answers with an alpha-beta search six moves deep — and because an extra turn counts as a move of its own, six moves deep can mean the whole of one long chain of its turns.

How to play

• Tap one of your six pits — the bottom row, the ones outlined in green. It must have stones in it.
• The stones are sown one at a time, counter-clockwise, into each following pit, including your own store but never your opponent's.
• Last stone in your own store: take another turn. There is no limit to how many you can chain.
• Last stone in an empty pit on your own side: capture. That stone plus every stone in the pit directly opposite goes to your store. If the pit opposite is empty too, nothing happens.
• The game ends the moment either side's six pits are empty. The other player sweeps their remaining stones into their own store, so a stranded pile is not a safe pile.
• On a keyboard, press 1 to 6 for your pits, left to right.

The extra turn is the strongest move in the game

Most beginners play Mancala looking for captures, and lose to someone who is quietly doing something else. The move that wins games is the free turn. A pit that holds exactly as many stones as it sits away from your store empties straight into it — your rightmost pit needs one stone, the next needs two, and so on up to six in the pit farthest from your store. Each one of those is a move that costs you nothing: you bank a stone and you are still on move.

That is why good players scan right to left. Play the pit that needs one stone and the pit beside it now holds one more than it did, which may be exactly what it needs. A board can be walked from one end to the other in a single turn, six free moves in a row, while your opponent watches. When you are choosing between two decent-looking moves, the tiebreak is almost always: which one leaves an extra-turn move standing for next time, and which one destroys it. Sowing past your store into your opponent's pits does the opposite — it feeds them, and it wrecks your own counts.

The capture is the other half. Landing your last stone in an empty pit on your own side takes that stone and everything in the pit facing it, which in the middle game is regularly six or eight stones at once. Two things follow. First, an empty pit on your side is a loaded trap, not a hole — keep one, and keep track of what is stacking up opposite it. Second, the same rule points backwards: a fat pit of yours sitting opposite an empty enemy pit is a robbery waiting to happen, and the fix is to play that pit before it is taken, or to fill the pit you were going to be captured into.

Then the ending, which decides more games than it should. The game stops the instant one side's pits are all empty, and the other player sweeps whatever is left on their side into their own store. So the last phase is a race with a peculiar shape: emptying yourself out is not caution, it is a gift, because it ends the game and hands the opponent everything they were still holding. Late on, keeping stones at home and refusing to push them across is worth more than a small capture — and if you can see that your opponent is nearly empty, the winning move is often to run yourself dry deliberately, cutting the game short while you are the one sitting on a pile.

None of this is new. Mancala is one of the oldest games in the world: rows of playing pits are cut into stone floors and rooftops across Africa and the Middle East, some at sites thousands of years old, and hundreds of local variants are still played today with seeds, shells or pebbles and holes scooped in the dirt. Kalah — the six-and-four version here, with the store rule and the capture rule — is the modern, commercially published tidy-up of that family, and it is the one that made it onto every school bookshelf.

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