Hey, thanks for the feedback!
The large amount of lag is purely due to collision detection. In the next coming updates, I would be switching to quadtrees for iterating through the rigidbodies during collision detection, to make the engine 10 times faster!
The 2nd issue is known, well, to be honest that’s just how verlet integration works! A work around would be to set friction of all rigidbodies stacked on top of each other to 0 (
RigidBody:SetFriction()) and then set it back to normal when some other body collides with it, etc. But yes, this is something I wish to fix in the future!