I love the simple sound design of the game! I think there is something that I would wanna change is this: due to my large screen size, having to hover all the way to the bottom right of the screen to click the "Check solution" button was something I don't think I wanna do very much. Maybe implement a keyboard button press or move the button closer to the central play area?
Otherwise, I love this game, 5/5 stars for you!