Thanks for playing and thanks for the feedback! You're absolutely right about the xp bar, that's a great idea. About the difficulty I do have plans for stronger/harder wizards. I did implement the wizards circling the player and avoiding each other but that was too oppressive and I toned it down, this is supposed to be the first level. I'll add more levels with different themes, gameplay mechanics and environmental hazards.
Again, thanks for playing and I'm looking forward to the Goblin Game as well!