I just won my 1,000th game, so I wanted to come thank you for all the fun times. I hope you're having fun and doing well making the game for other platforms.
If there's still development happening, or a sequel planned, I'd love to see a couple things.
First is an undo button. I know you can restart the current round, but it's a lot of work to get back where you were, and it can be hard to remember all the moves to get there. Simple misclicks seem to cause undue punishment.
Second is a difficulty rating. I know you don't have an auto-solver (since you said you're not sure if every game is solvable) but you could crowdsource the data by having the game report when a seed is finished or abandoned. I'm quite sure some seeds are not solvable, and it'd be good to know that in advance. It'd also be quite useful in presenting the game to new players, letting them see seeds that have been completed by a higher percentage of users first. "Difficulty levels" could be brackets of percentages, like "easy" is 80-100% cleared, "medium" is 60-80%, etc. (However the data works out.)