I liked the game. The art really has that Undertale/Earthbound to it and the ethereal music is pretty cool! (plus the final boss music is sick! definetly a highlight of the whole experience.) The level design is pretty nice, but it's not that intuitive. A little feedback on the type of powerup you pick up would be nice as well (just a little text when interacting with the upgrade saying which one it is.) I feel like it's kind of messy that you need the shadow in order to actually be able to reach the switch on the final room to the left hallway, since you don't need the explosion in order to reach the switch in the shadow room. i went left instead of right at first and I ended up getting a bit frustrated that the room was too difficult due to the amount of enemies (shadow solved it no problem). Also, although I think it is a neat little detail, the fact that the shadow pushes my character back whenever it merges back got me killed a couple of times lmao.
The last thing I have to say is that the final boss is a little unforgiving. It would be nice to have a windup animation for some of his attacks so the player could get ready for whatever action he's about to pull off. (The ground explosions are a little too broken, since the windup animation is almost instant and there is no warning on where they are going to spawn.) And I think my bigguest critique is that you really don't let your mechanics made for the abilities shine in the final boss, since you basically just need to avoid him to lelt him consume his own energy until he basically kills himself, so really I just had to run around, and that is a little bit anticlimactic for a final boss fight (especially with such epic music).
That's pretty much what i have to say about it. Kudos to the whole team and I hope you can expand on the game's lore a bit further, since the characters really seem like they come from an amazing world!