Me and my wife have dumped a surprising amount of time into this in the last couple days. It is so meditative and delightful.
Are you done developing it? A few more features and I feel like you have one of the best things on the Playdate. I would love an undo or a mode where you could dump a tile you didn't like. Maybe like in Tetris where you can store a piece or two for later?
It would also be fun to have a mode where, when you overlap, the overlapped bit of the new tile doesn't place or gets placed behind the previous tile. It would make it so you could combine tiles in new and interesting ways.
That said, keep the base mode just the way it is. It's perfect. Love the game!