Sweet game. I like the design of the mage. Those moving trees in the background are a neat idea and give the game much more atmosphere!
I think you could improve some things:
1. You should definitely show the controls at the beginning of the game. I can't jump using the top arrow key, which is counter-intuitive. I had to test every button on my keyboard to find the right one.
2. I was missing some 8-bit retro music. But that might be build in later?
3. The game is nice to play but honestly, so fas as I've played, there is nothing distinguishing this game from other simple jump'n runs. Its just one of 1000000 other jump'n runs that have been published over the years. I think you should add a twist to it, like the mage being able to use his magic wand to overcome foes or something like that.
Good game so far. Keep working on it!