Wow, that was impressive. I did have an issue with the game not loading in Chrome, but it worked fine in incognito mode. I found most of the later levels to be quite challenging. Though, I did manage to beat all of them. The two levels before the introduction of the barbarian stood out in particular.
My main request would be a tooltip to be able to get basic info regarding a hero or enemy. A standalone build in Windows would be great as well. That way I can save it in my folder containing awesome games.