the rewards shouldn't be purely based on Kreds. Maybe add rewards that can be benefited by players who don't buy Kreds like: 1 hour free of a locked character or something.
A wonderful game but a little bit tedious and repetitive. It would be nice if the animal units changed appearance every time you upgrade them and a different aura for the last upgrade ( Hood the Rabbit- fires three arrows that has a chance to penetrate).
as said in the best comments at the top, this is the structure of a really good game. With a few improvements im pretty sure this would be one of those top-rated games
You get free classes every day.