this game is shaping to be great man, it's good that you also come here to get some feedback
here's something from me, maybe you should rethink the evolution stones system, there's little to be gained from battles and the best way to even explore is get 2 to 3 eggomons evolved to rush the encounters, I like the sprites of the unevolved versions but it's not practical to use them because they get obliterated
maybe you could implement an evolution meter and make the encounters with evolved mons be rare ?
if not that maybe the big battles could gift you 1 stone of the monster type
the stones system can also brick your run, I got like 5 mind stones and I could not find them till I went to the mushroom forest
just my 2 cents