Please leave input on balancing here!
I always like this kind of game! :)
There is some optimisation strategy, but I don't think there is any miracle technique, so in order to balance maybe you could make computer battle itself a lot of times and count the wins! You can make the computer use different strategy to test, and then even see how much thinking instead of playing random can have an effect.
Also it would be great to at least have the height in meters shown too.
Although it is a card game but it does not have too many strategy so far, all is you playing the best 3 cards with highest number (double the steal number) and end turn. What I would recommend is restrict the percentage growth and steal card, give it an condition like skip next turn or discard rest of your hands etc...
I've enjoyed it but it feels pretty unbalanced in steal characters favor. Grow focused characters feel like they either get a really good start or just lose. Which even then the steal characters can just make a comeback anyway. Where as grow characters feel like they can't really close the gap once they fall behind and if they get close it just gets stolen again.
This game has a lot of promise! I would love to see more variety of cards available. Cards to multiply the results of the previous turn, cards that add +1 to the effects of multi-stage cards. I think it would be nice to have 6 cards to select from. Maybe a card to add +1 to the number of cards you can play the next turn, stuff like that!