1. The basic rules don't state that there is no promotion.
2. I would like to know a kind of "par" value per puzzle. Either the best it can be solved in or the average or something like that. This would help in finding an optimal-ish solution.
"Only 12 moves! Best is 10"
Granted this will be displayed in a much better way over time.
I don't think I saw the #moves the first time, or at the very least the lack of a try again/try for optimal/try other puzzles button made the page seem terminal. I imagine the share button is prominently there to go for virality.
https://wafflegame.net/archive is a game that is very similar to yours. I like their layout. The archive with a score per puzzle and aggregated information at the top is fairly addicting.
Waffle puzzles give you a maximum number of moves, 5 more than optimal. I like that more than infinite moves with try again. I think "failing" gives attempting more meaning.