When a solitaire game gets stuck, it is often hard to tell whether an earlier move caused the problem or the deal was impossible from the start. You can replay it to investigate, but you may still be searching for a solution that does not exist.
Solvable mode removes that uncertainty about the opening position. It selects a deal for which our solver has found a winning path, leaving you to work out the moves. If you are going to spend an evening arguing with a deck of cards, it helps to know the deck has an answer.
What we check before dealing
Cards4.net uses offline solvers to try candidate deals. When a solver finds a solution, the seed that reproduces the deal can be stored in a library for that game and variant. Solvable mode chooses from that library instead of accepting an unchecked starting position.
Doing this work in advance means a new game does not have to wait for a solver to finish. It also makes the qualification specific: the deal was solved under a particular set of rules. A solution for Klondike Turn 1 does not establish that the same arrangement is winnable under Turn 3 rules.
The solver has a search budget, so a deal it fails to solve is not necessarily impossible. It may simply require more time or a different search. Our library contains confirmed successes; it is not a complete catalogue of every winnable deal.
What happens after the first move
Once play starts, the rules are unchanged. You still need legal destinations for cards, still have to manage limited space, and still do not get to see face-down cards in games that have them.
The opening guarantee also does not follow you through every decision. A move can close off the winning route, leaving a position that cannot be finished without going back. Solvable mode does not rearrange the remaining deck to rescue you.
Suppose you use the last empty column in Spider to hold a mixed sequence. That move may be legal, yet leave you without the space needed to separate cards elsewhere. Knowing the original deal was solvable gives you a reason to examine that choice, but it does not identify the exact move to undo or tell you what the alternative should have been.
This makes solvable deals useful for practice. You can revisit a branch in the game and compare what becomes possible after each choice. The question is smaller and more useful than wondering whether the whole deal was a lost cause.
A solution is not a difficulty rating
Some confirmed deals have forgiving routes; others require choices that are difficult to spot. A computer finding a path tells us that one exists, but it does not tell us how readily a person will find it.
At the same time, filtering deals through a solver changes the pool. Deals the solver can finish within its limits are more likely to appear than ones it struggles with. We therefore should not describe solvable mode as having exactly the same difficulty distribution as ordinary random play.
That matters when comparing results. A win rate from a library of confirmed deals answers a different question from a win rate on unchecked deals. Neither needs to be treated as the more respectable number, but the mode belongs alongside the result if you want the comparison to mean anything.
Choosing a mode for the session
Solvable mode is useful when you want to work toward an answer and perhaps return to the same problem later. Ordinary random play suits a session in which you are comfortable abandoning a deal without knowing whether it could have been won.
Daily challenges use confirmed seeds because players are comparing their approaches to one shared problem. They need a common starting position with a known solution, though that still leaves plenty of room for different routes and finishing times.
Availability depends on the game and its seed library. If a supported variant's library is missing, casual play can fall back to an unverified random deal and show a warning. That warning matters: the replacement deal has not passed the solvability check. Daily challenges require the library and do not use this fallback.
Choosing solvable mode means deciding what you want to spend your time finding out. When the interesting part is how to finish a difficult position, starting from a confirmed deal lets you concentrate on that question. You still have to play the cards.
FAQ
What does solvable mode change?
It selects the starting deal from a library of seeds for which an offline solver found a winning path. The move rules stay the same.
Can I still lose a solvable deal?
Yes. A winning path from the opening position does not mean every move preserves it. You may need to undo moves or replay the deal.
Are solvable deals always easy?
No. The solver finding a solution is not a human difficulty rating, although selecting only solver-confirmed deals changes the mix of positions you receive.
What happens if a solvable library is unavailable?
For a supported variant with a missing library, casual play can fall back to an unverified random deal and display a warning. Daily challenges require the library and do not use that fallback.