I did try holding the jump button - that one animal said I should. But it did nothing! [Trying it again now.] I mean, I guess it makes you jump a little bit higher than tapping? I would say, it’s a bit much to have both this mechanic and double-jump in the game. But I don’t feel I was held back by not using this consciously. I’m just not very good at this kind of game maybe? But I did enjoy it.
You could consider making different player characters in this game, with a bit different movesets and physics each. So you can add even more special moves, but complexity stays capped. It would also be fun trying to beat levels with characters other than the intended one.