Check out Spintronics, it's a game/kit for building mechanical analogs for electric circuits. It's coming out sometime this year from the same team that made Turing Tumble.
https://www.kickstarter.com/projects/upperstory/spintronics-...
https://www.kickstarter.com/projects/upperstory/spintronics-...
My 9 year old brother found it quickly too hard though.
It does a good job of introducing concepts slowly but they are in fact hard concepts if you're new to them. It is actually a bit of a challenge for adults too.
Mechanically, the game is good but a bit finicky to set each piece in place. That means the time between "I think I know what to do" and testing it out is a bit too long. Overall, I find it pretty fun though. (I also backed the spintronics kickstarter)