Thanks! There is only one level after the tutorial so that's why I made it harder :) It's not meant to be an acid-trip game haha, you are just a raccoon fighting toxins in a melon.
Large buttons can only be activated by a large player, and small buttons can only be activated by a small player. If the large version of the player cannot activate the button, try moving shortly after pressing it.
Skill issue. Joke aside I had the same problem when I built the game, I didn't notice it in Unity Editor because it allows your cursor to go off screen. Definitely an easy fix but had no time left. I'm glad you liked the game.