Your game was quite good, but I'd like to elaborate a little.
Your sound and graphic design was simple, yet effective. I especially like the design of the wizard. Furthermore, it was a good decision to play a calm ambient sound during the levels. I would have gone crazy listening to the same 20 second title loop over and over again, but i don't like silence either.
The enemy variety is quite low, wich made me predict the types of enemies before I revealed them. This goes hand in hand with my next point: I would throw some kind of npc in there which actually wants help and makes you lose if you hit it.
The flying part is fine, but I think some kind of fuel bar would help. Besides, I would let the players fly whenever they wanted, even in the air. Currently you have to hold the spacebar, but I somtimes wanted to let go of space and then fly again before touching the ground or falling to my death. Touching the ground would refill the fuel.
Sadly I couldn't play the easy mode because the menu buttons have no functionality after beating the game.
Don't take the criticism too hard, I had fun playing your game.