Completed the whole game! The game mechanics are really very interesting. So, you could actually make lots of levels... Maybe you should ask the user before closing the instructions screen? I didn't read them completely, but then, it was puzzle game, so that just increased the fun in the game.
The UI was simple and it was easy to navigate.
I would suggest you to add one or too more game elements (that's how puzzle games work), make lots of levels, and port it to mobile! That's if you want to continue working on this game...
Good luck, bro!