Forty Thieves: a one-pass game that punishes short-term play

Forty Thieves deals 40 cards face up into ten columns of four, leaves 64 in a stock, and gives you very little room. Cards build down in suit, move one at a time, and the stock goes through once. Every card you turn and cannot use sits on the waste pile and blocks the one beneath it. It is a game where the move that looks good now often costs you later.

We put a look-ahead player on 3,000 deals on this site's rules. Before each move it weighs up to 300 future positions, but it cannot see the stock and never takes a move back. It won just 5.8% (174 of 3,000; 95% range 5.0%–6.7%) and got 34.3 of the 104 cards home on average (95% range 33.5–35.1). That is a floor, not a human win rate. A person with Undo and a plan should do better.

We did not run a purely greedy player or an all-seeing solver on Forty Thieves, so this page cannot show what planning adds from one bot to the next. The figures we have come from one short-sighted planner. Below we use them to show where a longer plan has room to improve on it.

At a glance: what a short look-ahead achieves

Two-thirds of the cards never reached home in a typical game. That gap is where planning lives. Our player had no Undo, and every choice about when to turn the stock was made blind. You can do better on both.

Forty Thieves rules on this site

• Cards: two standard decks, 104 cards.
• Tableau: ten columns of four, all face up.
• Stock: the remaining 64 cards, turned one at a time onto a waste pile. The top waste card is playable.
• Redeals: none. The stock goes through once.
• Foundations: eight, two per suit, Ace to King.
• Building: down by one rank in the same suit.
• Moves: one card at a time.
• Empty columns: any card.

Where planning beats the bot

Bank the easy Aces, then stop and think

57.3% of our deals had an Ace ready in the opening tableau. Play it at once. A foundation card never needs space again. Then plan the rest before you turn a single stock card.

Turn the stock only when the table is ready

Our player flipped a stock card whenever no tableau move improved its score. A planner turns the stock only when there are landing spots for what might come. Every unplayable card buries the next one.

Aim for an empty column first

An empty column is the only extra space this game gives, and any card can use it. Choose the column with the fewest useful cards and clear it early. Moving one card at a time, a single gap lets you shift a short same-suit sequence.

Same-suit links are worth protecting

Only same-suit builds are allowed, so each column soon "belongs" to the suits in it. Before adding a card, check that you won't need to dig underneath it soon.

Use Undo as your look-ahead

Our player could not see the stock and never took a move back. You can turn a card, see it, and undo if the timing was wrong. That alone gives you more information than the bot ever had.

Expect a long game

The player's wins took 277.3 moves on average. Winning at Forty Thieves is patient work.

Classic short-term mistakes

• Turning the stock "to see what comes". Each wasted card blocks the waste pile for the rest of the game.
• Filling a gap with one stuck card. A gap is often better used to reorder a short same-suit run.
• Racing one foundation. With two piles per suit, cards still useful as landing spots can wait.
• Forgetting there is no second pass. Take the waste cards you need while they are on top.

Forty Thieves on spidersolitaireonline.us

The game is free in any modern browser on computer, tablet or phone, with no account. Unlimited Undo lets you see a stock card and still change your plan. Hint, Restart and Auto Play are there too, along with fullscreen and zoom for ten columns of cards, drag or tap to move, a counter for wins, time and moves, and settings for sound and table color.

How we ran the study

The spidersolitaireonline.us team ran this test in September 2026 on this site's own Forty Thieves rules. The program is written in Python. An AI assistant, Claude by Anthropic, helped write and review the code and draft this page. Every figure comes from running the code.

1. Rules traced in the site code: forty cards face up in ten columns of four, a 64-card stock turned one at a time with a single pass, same-suit building, single-card moves, any card in a gap.
2. 3,000 numbered deals, seeds 1 to 3,000.
3. A floor player. Before each move it weighs up to 300 future positions using only visible cards. It scores foundation cards highly and cards resting on lower cards badly, and gives small credit to same-suit links, empty columns and a short waste pile. It never undoes. When nothing improves its position, it turns the next stock card.
4. Every deal played to the end, counting wins, cards home and moves.
5. No published figure to check against. Forty Thieves is not in Blake and Gent (2026). The solitairex.io site lists Forty Thieves in a tier at 11% or less, with no method given.
6. Limits. No greedy baseline and no all-seeing solver were run, so we cannot say how much a deeper plan adds in numbers. The 5.8% is a floor.
7. Margins of error are 95% Wilson score intervals for percentages and normal intervals for averages.

Forty Thieves questions

Is 5.8% my chance of winning?

No. It is what a weak player with no Undo managed. With Undo and patient planning you should beat it.

Does the stock come round again?

No. On this site it goes through once.

Can I move a whole run?

No, only one card at a time. That is why empty columns matter so much.

What should I play to practice?

Eight Off trains same-suit thinking with room to spare. FreeCell Two Decks is another two-deck game with every card visible. For real greedy-versus-planner comparisons, see Spider. All games are on the home page.

By Admin, spidersolitaireonline.us (Solitairen OOD). Research run September 2026.