@neauoire This isn't it, but you made me remember Algodoo (or Phun how it was called before). Oh god how much time me and my friend wasted when we were early teenagers.
It's like a sandbox with physics engine, with gravity, wind, fluids, magnets, springs, different materials and different forces. People did basically anything in it, from simple games with fun physics to complex gun models with working insides (like it shoots a bullet because there is reaction happens inside) and car engines.

@neauoire sodaplay was SO GOOD, I was obsessed with this in highschool