I should have added a fail safe for that but didn't. 3 stars should have been the max level and I didn't think anyone would have gotten to 4 stars. I will fix this. Do you think it would be more fun to be able to level to 4 stars?
Since 3 units with the same ammount of start are needed to get a unit that has one star more and there are only 11 unit slots (3 active and 8 reserve) and the are not that many levels, i think 3 star is at the moment good eough.
Also i just won with a 3 star blue robe wizard and a pair of 3 star monks.