It's very good. I played a puzzle on my phone. I wish there was pinch-to-zoom, and the pieces autorotating when I selected them is almost cheating. I was able to connect a lot of pieces by just dragging a piece over a pile and seeing what auto-snapped. I also inaverdently connect pieces that way too. I don't know if those are solvable issues without impacting ease of play.

Those may not even be big enough issues to worry about. Someone wanting to pay for a subscription probably isn't the person who is going to want to "cheat", though inadvertant pieces snapping together might take some of challenge/fun away from the user.

Maybe if the user has a mouse with a scrollwheel, the scrollwheel could be used to rotate the piece, but then you wouldn't be able to use the scrollwheel for zoom (I don't know if you are already, as I'm on a phone), or you could just use keyboard keys to rotate.

Maybe only have the piece the user is "holding" snap to another piece of the other piece is not being covered by any other pieces. (If there is a stack of pieces, and the user drags a piece over the stack, the dragged piece should only snap to the piece on top of the stack if it is a match. Do not let any covered matching pieces snap.)

I hope the feedback helps. Again, great job!