I liked the idea and it could easily become a game for educational purposes (and I don't mean it in a bad way, quite the opposite). I liked the calculator visuals, but I think it would help if the sound for each input was more "button like", because based on the theme it felt out of place. Something that I think that would add to the theme is if the player was seeing the calculator from the inside (even if the numbers weren't mirrored, of course). Good job