There already is a score counter and the amount of carrots, bok choys and lives are also displayed on the top right of the screen but I guess you can't see them? I had trouble with scaling the game here in itch.io because when the game window was smaller, it would not display the whole game and the borders were left out. For me it works fine on full screen mode though, but after reading your comment it seems that it's not the case on every device :(