I really liked this game! The sounds and the art were really nice and gives the game a nice charm to it, and the game itself was a lot of fun to play.
Since you are planning to release the game on mobile, here are some suggestions that I feel may help you improve the game:
- Sound effects for each kind of guess, one for too high and one for too low, with perhaps a visual of some sort (such as a flash, or even better, animations of the wizard signaling with his hand and body language).
- A non-plain background
- When I press "Enter", I lose a life but the guess indicator doesn't show until I press the "Guess" button. You should handle both cases as some people may find it more convenient to press the "Enter" button to submit a value from a text field.
On a side note the apprentice wizard has only 11 possible numbers and you give the player 10 guesses which is far too many.