Hi, 

I'm new to itch.io, and I wanted to know  if this is a place where I can put gameplay mechanic only demos for others to play with.
What I mean is, it's not a full game, just level(s) where you can use cool mechanics like Kratos's Leviathan axe, or Thanos's Gauntlet powers.  

Thank you

You're welcome to, as long as you categorize and describe your project well. People will want to know what it is.

Welcome!

YES! itch.io is open for all such little demos and toys too. Your demo sounds fun by the way.