In Nimble Quest, you kill monsters and you pick up gems. Each hero has a progress bar underneath them that shows how far they are from the next upgrade (star). I tried to figure out exactly how this progress is calculated by comparing different numbers (gems, kills) before and after a game. The change in 'experience' appeared to be close to the number of gems I picked up, but not exactly equal. So how is this progress calculated?
Is it based only on these two factors (gems and kills), or only one of them, or does it involve other factors, such as what level you get to (do higher levels give you more experience per monster as well as more monsters in the level overall), how many max/current heroes you have, or even which character you are using (do all heroes progress at the same rate)?
A source from Nimblebit (the developers) would be ideal.
Edit: Although an answer has been posted saying that killing monsters does not contribute to hero progess, I decided to leave in the relevant paragraph as it lists a number of possibilities.