This is just REALLY good oh my god.
The Snake is kind of overtuned right now because the venom affects only the opponent (but you probably know this); the robot and starfish seem way too strong at 5 critters, but I think the game gets much more interesting with battlefields of 6. Bird that reduces opponent's size of the field seems very powerful as well, while Venos seems downright unplayable? Can't really tell because the AI isn't very good, I really want to just binge play it with other humans to really break it in half.
I wish I could have a boardgame version of this, I'd play it a lot. Even as is. For real. Strangely gives Faraway vibes crossed with Mindbug, even if it's mechanically very different from both? I just really really love this game, astonished you managed to put something like this out in just 72hs, with this amount of content. Balance is not even that out of whack. Gorgeous work.