Calculation

Calculation is the arithmetic game. Four foundations, each climbing by a different step — one, two, three, four — all wrapping past King and coming round again, so every foundation wants a different rank at every moment and you have to hold four sequences in your head at once.

What makes it a genuine skill game is the waste piles: four of them, and a card placed on one can never move except to a foundation. So the game is not really about the arithmetic, which you learn in a few rounds. It is about deciding, forty-eight times, which pile to bury a card in — and a skilled player wins two games in three where a careless one wins almost none. Few solitaire games separate good play from bad so cleanly.

An Ace, a two, a three and a four are laid out as foundation bases, and each builds by its own interval: the Ace runs A-2-3-4 and so on, the two runs 2-4-6-8, the three runs 3-6-9-Q, the four runs 4-8-Q-3, each wrapping past King and continuing. Cards come off the stock one at a time and either go straight to a foundation or onto one of four waste piles. Once a card is on a waste pile it can only leave for a foundation, never for another pile — so where you put it is a permanent decision.

This is the most purely calculating game in the catalogue and the one where skill matters most. Because a card on a waste pile can only leave for a foundation, every placement is a commitment, and the whole game is about not burying a card you will need soon. Keep one waste pile as clean as you can for cards that are nearly playable, and dump genuinely distant cards together on another. Know the four sequences cold — the four-interval line in particular is unintuitive — because misremembering which rank a foundation wants next is what loses games here. Wikipedia notes a very skilled player wins two in three even at the hardest setting, so the ceiling is high and the gap between careless and careful play is enormous.