Mini-metroidvanias like this are so fun to play! You picked a great mixture of abilities that are all unique and enjoyable to use. Using Big Mode to stomp enemies is really satisfying in particular, and the dunkey crab-kick is perfect.
The little touches go a long way, like the animated background, unique normal/big/dunkey/rocket animations, the enemy sprites that change as they take more damage, and the cool hand-animated smoke effect while you're transforming. Also I can't get enough of that falling animation with the flailing feet, haha. Very well done!