Pretty entertaining game.
I like the concept for your game, there haven't been too many games I've played that have a medieval setting. I thought the animation and conrols were both very smooth. The upgrades were a nice addition to the game, they gave me a reason to keep coming back to play. The in-game achievements were fun missions to accomplish as well.
The only thing I disliked about the game was that it got repetitive after the first couple of waves. The new enemies every few levels were nice, but just the running and shooting didn't add much variety to the gameplay. Besides that, I found the game to be quite enjoyable.
I'm not trying to overanalyze this, but I have one question. If the enemies have the abilities to teleport and shoot fire, how can this be classified as "medieval'? It just struck me in the middle of the game, and I don't want to come off as mean when I sat that, I'm just curious about it. Anyway, keep up the great work!