Plenty of sorting puzzles generate a board at random and hope for the best. That is how you end up on level forty with a position no sequence of moves can win, staring at a restart button and wondering whether you missed something.
Stack Cards Sort does it the other way round.
Backwards from a finished board
Every level starts life already solved: each column holds four tiles of one colour, sealed and tidy. The generator then takes that finished board and plays it backwards, undoing legal moves one at a time until the board looks properly scrambled.
Because every step of the scramble is a real move played in reverse, replaying those steps forward solves the level. The solution is not something we hope exists. It is the thing the level was made out of.
Where par comes from
The scramble leaves behind a witness: the exact sequence of moves that unpicks it. The length of that sequence is the level’s par.
That has a pleasant consequence. Par is never a guess, and it is never a number tuned by hand until the difficulty curve looked right on a spreadsheet. It is the length of a solution we can show you.
It also has an honest caveat: par is a good solution, not a proven shortest one. Our solver is not certified minimal. If you finish a level under par, you did not exploit a bug — you found something better than the generator did, which is a perfectly nice thing to have happen on a Tuesday.
The move budget is not par
You are not held to par. The move budget you actually get is par plus a cushion: at least six extra moves, and more on longer levels, where it scales with the size of the problem.
The cushion exists so that thinking is allowed. You can try a column, decide it was wrong, and undo without the level punishing you for the detour. It is only on the tightest, longest levels that the budget starts to feel like a constraint, and by then you have had eighty levels of practice.
Stars measure efficiency, not speed
There is no clock anywhere in the game. Stars come from one number: how many moves you used against par.
- Finish at par or better, and you get three stars.
- Finish within one and a half times par, and you get two.
- Finish at all, and you get one.
One star still means you solved it. That matters more than it sounds: the star rating is feedback, not a grade, and a level you cleared is a level you cleared.
And if you run out of moves
You do not lose because the board dead-ends. The board cannot dead-end — there is always a legal move available while tiles remain. The only way to fail a level is to spend the whole budget.
Which is exactly what Relax Mode removes. Turn it on in Settings and the budget stops counting against you: the same levels, the same solutions, none of the pressure. Some evenings that is the game you want.