[desdiv]

Some starting conditions have multiple solutions. A trivial example would be a 2 x 2 game with two "2" at opposite corners.

[ddlatham]

I believe that such instances are not generated by this game, however.

[dmurray]

I had an example with two possible solutions (3 empty spaces were left, and either BRB or RBR would have satisfied the conditions). I meant to take a screenshot after finishing but the final position fades out (and adds numbers everywhere) so I should have done it before the end.