I think it's a good game idea, but there's very little visual help to tell you what's happening while you're capturing creatures.

I think the major game idea is very interesting, but I couldnt really do anything. I captured every creature and then nothing happend. Also there was no new log entry or anything similar. Am I missing something?

I liked the idea of capturing creatures to create a new ability, and having a shrink ray fits the theme in a very clever way. I do wish the keybinds were shown somewhere besides the keybinds menu, especially when I have to fully restart the game to get to the main menu and, by proxy, the keybind menu. 

Exploration could have benefited from not blocking off areas with invisible walls, this led to a bit of confusion where I wasn’t sure where to go for a bit, not knowing that an invisible wall I had run into earlier had quietly disappeared at some point.

(And a bonus nitpick: the menu button sound is a bit ear-piercing; I would recommend turning it down or using a different sound in the future.)

I didn't play very far in unfortunately because I simply did not like trying to get through the cave area with how it was designed which is a shame because I really like the idea you got here and would like to see it further developed! I like the idea of having to find funny creatures and studying them to get your upgrades that's fun. I also spent an embarassing long time realizing there was a sprint button lol.

My two primary suggestions for stuff to focus on should you decide to polish this more:

• You'll want to work on sharpening the physics a bit though, the player feels too slippery for how heavy they are (my recommendation is lowering the horizontal acceleration sothe player is less likely to launch themselves directly off the edge of platforms). Jumping feels "too fast" but its hard to gauge whether that's because gravity is too heavy or the upward velocity is too much (you can tweak this as you please though, its tricky to get something that feels "just right" for what you want!)
• The cave area is too spacious without actually having anything going on in it aside from too much platforming that isn't doing anything other then "make this one tile jump under a ceiling then get pushed off by this creature who can just snipe you if you time it badly". I think that sort of platforming challenge just isn't really the right call for this sort of game (would probably be fine in other games for the record).

Keep at it! I think you got something Cool here, even if I didn't stick with it.