Solvers

By the end of this page you will know how to ask CardTray whether a game can still be won, what each answer means, and where to watch a winning line.

What "winnable" means

The solver knows the whole deal, including every face-down card and the order of the stock. Winnable means a win exists when all of that is known. You can't see those cards, so a game that can be won can still be lost by an honest player. That is normal, and it is why the answer is a guide rather than a promise.

The solver cannot settle every deal. Large games in particular often come back Unknown, which means only that the solver ran out of room before it found an answer — not that the game can't be won.

Asking during a game

The solver is available on games you start from the Game Gallery. Press Is this winnable? in the top bar. The first time you use it on a game in progress, CardTray asks Use the solver? — Using the solver on this game means it won't count toward bests, streaks or achievements. Choose Use the solver to go ahead. The game is then assisted: it still counts toward your played and won totals, but not toward personal bests, streaks, the Daily calendar or achievements. See What counts.

You can keep playing while the solver works; the button reads Checking…, then Looking deeper… if it needs a second pass. The answer arrives as a message and as a label in the top bar, tagged with the move it is about (for example Winnable · as of move 42). Check again asks about the position you are in now.

On a Beta game, every answer adds: This game is in Beta, so its rules may still change.

The button is hidden on the Daily Challenge (so an answer can never cost you the day's streak) and on games the solver does not support.

After a loss

The end-of-game window and the pause menu both have Was this deal winnable? It runs only when you press it, and it asks about the original deal rather than your last position. A finished game is already scored, so asking changes nothing in your records. Try again from the same deal stays the main button.

The Solvers screen

Solvers in the sidebar lists every solve. Active rows show the game, the deal, the move it started from and a progress bar, with Cancel. A solve that needs a second, deeper attempt stays on one row and says Looking deeper…. Recent rows show the answer — Winnable, Not winnable, Unknown, Unsupported, Error, Failed or Canceled — with Watch solution (Winnable answers only), Open game and Remove. Retry appears only if a solve failed. Clear finished hides finished rows; the answers are kept, so asking about the same position again is instant.

Solvers run one at a time by default. Change that with Solvers running at once in Settings. Starting a solve needs bandwidth sharing to be on (see How CardTray is funded); if you turn sharing off, solves that are already waiting stay queued until it is back. Watching a solution that is already stored does not need sharing.

Watching a solution

Watch solution opens the replay player over your own moves up to the position you asked about, followed by the winning line. Scrub, pause or step through it at 0.5× to 8×, exactly as in a replay. Resume from here takes over from any point as a new game, which is assisted like any game that used the solver. If the game's rules have changed since the answer was found, the player shows Recorded on an earlier version of this game — can't be replayed. and offers Solve again.

What usually goes wrong

• The Is this winnable? button is missing. It is hidden on Daily Challenge games and on games the solver does not support.
• A solve stays queued. Bandwidth sharing is off, or another solve is running and Solvers running at once is 1. Turn Share idle bandwidth on in Settings.
• "This one's too big to decide." The deal is too large to settle. Nothing more can be tried.
• Watch solution is missing on a row. Only Winnable answers have a solution to watch.
• A row says Error: "The solver and the game checker disagreed." That is a bug in CardTray, not in your game. Please report it through Feedback.