Hi, so my thoughts on this game are as follows:
1. I like the theme, a sort of toxic creature fighting against other toxins that have teamed up to destroy it, possibly because it is stronger than the rest, resembling a threat.
2. It also seems that this takes place in a laboratory, so it could be that you are controlling a text subject which is trying to escape. Also, the story could evolve, as you fight against different toxins, bosses etc. until you reach freedom of the outside (and take over the world???) Or perhaps a scientist is performing tests on you, which is similar to the plot of a flash game series: "Test Subject", by Nitrome.
3. I like the upgrade system, altough you could definetely add more to it. For instance, something I would enjoy would be multi-directional shots (basically, shooting in more directions at once) or a dash-like ability, which also makes you invulnerable to dmg for a brief period of time (this is excellent for adding depth to gameplay).
4. This feels like a prototype, but with potential for great success! The Playstore has been flooded with similar games, featuring a protagonist battling against hordes of enemies and trying to survive as long they can (e.g. "Magic Survival", "Brotato", "Vampire Survivors" etc. being among the most popular).
To end this (long) review, I enjoyed your game, however it could definetely use some original elements to stand out from the crowd, especially in case you want to create a marketable product. I hope this review has helped you in any way, and thank you for reading until the end. :)