What aspects of coding?

Turing Tumble is a marble run puzzle game that's Turing complete, i.e. in the abstract sense, it can compute anything a computer could. It implements bit flippers, logic gates, and memory using falling marbles and levers. Completely mechanical and very tactile.

For textual programming, check out Hedy, a language designed for the classroom. It stands out vs others like Scratch or Snap because Hedy is gradual. A presentation by its creator