Good:
- Controls very well. Jumping, aiming, and shooting all feel good.
- Is the whole world made of meta-balls? If so that's amazing, and it definitely looks great. I like how you varied the zones by making them more or less "goopy". The wall morphing enemies killed me a few times because I was gawking at the effects.
- I enjoyed the music. It matched the art-style really well.
Bad:
- It's entirely linear, so not really a metroidvania.
- Related to the previous point, none of the upgrades seemed necessary. They were all helpful combat buffs, but they didn't open any new pathways. The beam, in particular, felt redundant.
- The explosion on the wall morphers looked quite small, but seemed to hit me from the far side of the screen. That was a little confusing.
Overall, this was a very enjoyable platformer, and I'd love to see you make it into an actual metroidvania. The upgrades you have would make great optional upgrades to encourage exploration. Maybe add some movement abilities that allow access to new areas. You have really cool graphical tech in this game, so it would be good to see abilities that tie into that. Maybe morphing through certain walls, or melding into walls to climb them.