Spider, four suits: 104 cards, eight runs, and the steepest climb on the site
Four-suit Spider uses two full decks exactly as printed: two of every card in every suit. Unlike the other 104-card games here, it also hides all but one card in each column at the start. That combination makes it the hardest thing here for a program that cannot see the face-down cards.
Our look-ahead program won 0.2% of 2,000 deals (95% range 0.1%–0.5%), 4 games in all, and completed 0.04 of 8 runs per game (0.03–0.06). Yet the published estimate for a solver that sees every card is 98.5% winnable (±1.5%; Blake and Gent 2026). The one-deck cousin, Spiderette, is published at 99.620% (±0.018%) on the same kind of measure. So with full information, adding the second deck barely dents winnability. Without it, the game is a long climb.
At a glance: four suits, one deck vs two
| Measure | Result | 95% range / margin | Sample |
|---|---|---|---|
| Our program's win rate, 2 decks | 0.2% | 0.1–0.5% | 2,000 games |
| Runs completed per game, of 8 | 0.04 | 0.03–0.06 | 2,000 games |
| Published, all cards known, 2 decks (Spider) | 98.487% | ±1.513% | Blake and Gent |
| Published, all cards known, 1 deck (Spiderette) | 99.620% | ±0.018% | Blake and Gent |
| Emptied a column before the first deal | 0.3% (6 games) | 0.1–0.7% | 2,000 games |
| Won when that happened | 2 of 6 (33.3%) | 9.7–70.0% | 6 games |
Our figure is a very weak floor; the published figures are ceilings for play with hidden cards revealed. Spiderette is not played on this site, and we did not simulate it ourselves.
What the second deck means in four suits
Every card has exactly one twin of the same suit. When your 7 of clubs needs an 8 of clubs, there are two, and often one is buried. Tracking which twin is reachable is the four-suit version of the skill that FreeCell Two Decks asks for with every card in view.
The rules here
- Cards: two decks, 104 cards, all four suits.
- Layout: ten columns of six and five, bottom card face up.
- Stock: 50 cards, five deals of ten; not onto an empty column.
- Building: any card on one rank higher.
- Moving: same-suit runs only.
- Empty columns: any card or movable run.
- Completed runs: leave the table automatically.
Climbing the four-suit game
Count the twins
Before building off-suit, check whether the same-suit twin is visible. If it is, wait for it.
Turn cards over first
Almost all 104 cards start hidden. Each revealed card tells you where a twin is.
Protect empty columns
They are the only way to sort mixed runs. Do not deal until you have used them.
One finished run is a real milestone
Our program averaged 0.04. If you finish even one, you are ahead of it.
Undo is the whole game
The 98.5% ceiling comes from trying lines and backing out. Undo is the closest you get.
Spider on freecell-two-decks.com
Free in any modern browser on computer, tablet or phone, no account. Hint, unlimited Undo, Restart, Auto Play, zoom and fullscreen, drag or tap, a count of wins, time and moves, and sound and table color settings.
How we measured it
The freecell-two-decks.com team ran this simulation in September 2026 on this site's Spider rules.
- Rules from the game code, four suits.
- 2,000 deals from seeds 100,001 upward, after tuning on deals 1–30.
- A look-ahead program with face-up cards only, no Undo; a very weak floor.
- Published ceilings from Blake and Gent (Journal of Artificial Intelligence Research, 2026) for Spider and Spiderette.
- 95% ranges by the Wilson score method; the six-game subgroup is too small to lean on.
Python 3.11, standard library only. Claude, an AI assistant by Anthropic, helped write and review the code and draft this page; every figure comes from running the code or from the cited paper.
Questions
Can four-suit Spider be won?
Almost always in principle: 98.5% with every card known. In practice it is the hardest game here.
Would one deck be easier?
With full information, only slightly by the published numbers (99.620% for Spiderette). We have no program figures for one deck.
What next?
Practice on two suits or try FreeCell Two Decks, where every card is face up. All games are on the games page.
By Admin, freecell-two-decks.com (Forty Media). Research run September 2026.