I liked it lol (especially graphics part, though UI like buttons dont fit game style)

This game is mis-tagged, both here and on itch. There is only a Windows download. I tried running it in wine though, and it worked. I am glad I didn't give up trying to get it to run: We had the same idea. Running IN space! (Except your astronaut has a rounder butt and my runner is not endless)

It looks like you enabled physics on your character so he bounces a bit when you reach the ground. If you make a post-compo version, maybe tweak that part so he doesn't bounce, or handle the ground-collision manually, or maybe do something interesting with the bouncing.

The slide animation reminded me of commander video in the first bit.trip.runner. Maybe that was a reference.

The levels generation is probably when you can improve the most. As is, sometimes there is an alien and a spike at the same time, and sometimes the screen is completely empty for a couple of seconds. Maybe there could be things you jump on top of, or maybe that's too much like bit.trip.runner.

At any rate, this is better than my first solo game. Keep it up!