Platformer always fun and when you can use a slime, that's extra points. If you let me give some tips so you can make a better experience.
- More gamejuice, like screen shake, dramatic zooms, borders in enemies, that kind of stuff, make the game visually stunning even if graphics aren't so details.
- Don't underestimate the camera, which can be a powerful ally for the experience, move from point to point so the player feels like he is in this world, not that he owns the world.
- This is for your character, He is a slime so make it bobble a little bit and more cute (Because the robots are cute)
- When you use assets try to make theme more cohesive. That give a extra polish to you game.
I feel happy you are open to criticism, (If not you can ignore all the bulletpoint and Have a nice day) I hope you can keep growing in game dev world. Keep it up.