Scorpion Solitaire: most deals cannot be won, even with perfect sight
Scorpion looks a little like Spider in a single pack: seven columns, a handful of face-down cards, and the aim of building each suit from King down to Ace inside the tableau. It plays very differently, though, because you may pick up any face-up card together with everything on top of it, whether or not those cards are in order. That freedom sounds generous. Our results say otherwise.
We gave a solver the kind of advantage no player has: it could see all the face-down cards and the three cards held back in the stock. Even so, across 3,000 deals it proved 67.5% impossible, won 12.9%, and could not decide the remaining 19.6%. So under this site's rules at most about a third of Scorpion deals can be won, and probably fewer. The University of St Andrews study, our usual point of comparison, does not include Scorpion, so we cannot set this against a published figure.
What the solver found
| Measure | Result | Deals |
|---|---|---|
| Solved (solver sees every card) | 12.9% (95% range 11.7–14.1%) | 3,000 |
| Proven impossible | 67.5% (95% range 65.8–69.2%) | 3,000 |
| Undecided when the search limit was reached | 19.6% | 3,000 |
| Most that could be winnable | 32.5% | 3,000 |
| Deals with at least one King face down | 65% | 3,000 |
| Published figure (St Andrews study) | None: game not covered | – |
Because our solver could see cards that you cannot, these are ceilings. A real player, working with the face-down cards hidden, will win less often than the solver.
What makes Scorpion so hard
Only Kings can fill a space
An empty column is only useful if a King is ready to go into it. When the King you need is buried, the space sits idle.
Building strictly in suit
Every card has exactly one card it can go on: the next higher card of its own suit. If that card is underneath it in the same column, you have a knot that can be very hard to untie.
Very little in reserve
There are only three cards in the stock, dealt once onto the first three columns. There is no waste pile and no second chance.
Buried Kings matter less than you'd think
Two deals in three start with at least one King face down. You might expect those deals to be much worse, but the solver's success barely moved: 14.0% solved with two or more Kings face down (645 deals), against 12.1% with none (1,045 deals). The difference is within the margin of error, so a buried King on its own is not what sinks a deal.
The rules on this site
The layout
One pack. Forty-nine cards are dealt into seven columns of seven. In the first four columns the bottom three cards are face down; everything else is face up. The last three cards form the stock.
Moves
- A card may be placed on the next higher card of the same suit: the 5 of clubs on the 6 of clubs.
- You may move any face-up card, taking with it every card on top of it, in or out of order.
- Only a King, with whatever sits on it, may be moved into an empty column.
- At any time you may deal the stock: one card onto each of the first three columns. This happens once.
- When a full suit runs from King down to Ace in a column, it is removed automatically.
Winning
Complete and clear all four suits.
How to give yourself the best chance
Uncover the hidden cards first
Only the first four columns hide cards, three each. Getting them face up early tells you what you are dealing with.
Look for the knots
Scan each column for a card sitting above the card it needs to go on, in the same suit. Those are the positions that decide the game, so plan them before anything else.
Save an empty column for the right King
A King that brings a long tail of useful cards with it is worth far more in a space than a lone King.
Choose your moment for the stock
The three stock cards land on the first three columns whenever you choose. Deal when those columns can best absorb them, not simply when you get stuck.
Don't take a loss personally
Two deals in three were proven impossible even for a solver that saw everything. If a game dies, it may well have been dead from the start.
Scorpion on solitaire-free.uk
You can play free in any modern browser on a computer, tablet or phone, with nothing to install and no sign-up. The cards are large and readable with a zoom control. Hint, unlimited Undo, Restart and Auto Play are to hand, cards can be dragged or tapped, and wins, time and moves are shown for the current game. Sound can be turned off; fullscreen mode and a choice of table colours are available too.
How we ran the research, step by step
- Rules from our code. Seven columns of seven, three face-down cards in each of the first four columns, a three-card stock dealt once to the first three columns at any time, in-suit building, any face-up group moves, Kings only into spaces, completed suits removed.
- Rebuilding the game. We wrote Scorpion in Python, sharing code with our Simple Simon program, and built a solver.
- Numbered deals. 3,000 deals (seeds 1 to 3,000), each shuffled from a numbered seed.
- A solver with perfect sight. The solver knows the twelve face-down cards and the three stock cards. That makes it stronger than any real player, so its results are ceilings. It searched up to 200,000 positions per deal.
- An independent cross-check. Deals the solver called impossible were re-checked on two sample deals with a completely separate brute-force search, which agreed.
- Checking against published research. The St Andrews study (Blake and Gent, Journal of Artificial Intelligence Research, 2026) does not cover Scorpion.
- Margin of error. The 95% range for "proven impossible" is 65.8% to 69.2%.
- Limits. Almost a fifth of deals were undecided, so the winnable share lies between 12.9% and 32.5%. And because the solver sees cards that are hidden from you, your own results will be lower still.
Behind the numbers: the code
Scorpion's solver is in spiderlike.py, a Python 3.11 module with no outside libraries that also handles Simple Simon. It uses best-first search: the most promising position is always examined next, and a set of positions already seen stops it repeating work. The separate cross-check is verify_scorpion_bruteforce.py. A shared runner spread the 3,000 deals over the cores of one machine with Python's multiprocessing, taking about 48 minutes. Ranges are Wilson score intervals. Claude, Anthropic's AI assistant, helped us write and review the code and draft this page. The figures come from running the solver, not from the AI.
Frequently asked questions
How many Scorpion deals can be won?
On this site's rules, at most about a third, even for a player who could see every card. At least two in three are impossible.
Can I really move cards that aren't in order?
Yes. Pick any face-up card and everything above it comes along.
Why can only Kings go in empty columns?
That is how this site's game is coded. It makes empty columns much harder to use, so plan before clearing one.
Is Scorpion like Spider?
Both build complete suits down from King to Ace in the tableau, but Scorpion uses one pack and lets unordered groups move.
What is kinder?
Try Simple Simon, also one pack and all about suits, or Spider Solitaire. Browse everything on the games page.
By Admin, solitaire-free.uk. Study date: 19 September 2026.