To be honest, the first thing that came to my mind was a competition. Who can destroy more opponents and grow more or something like that. I think for starters you can try to do this in the mode where you need to pet the character. Just my opinion, your idea is not bad either, but I want to have more sense of competition in the game than just a leaderboard. And I forgot to say that the game is just awesome, thanks for the work, if I have a better financial situation, I will definitely think about supporting you a little