How is the local blockchain implemented?

[snow elk]

It seems to me like the ledger rules are reimplemented. Is this the case, or does it reuse the OCaml code through js_of_ocaml?

[prime smelt]

It reuses OCaml code https://github.com/MinaProtocol/mina/blob/develop/src/lib/snarky_js_bindings/lib/snarky_js_bindings_lib.ml#L2420