The compiler is implemented in Horse64, and the runtime is implemented in Horse64 Root.
Horse64 Root instead?Ideally, use both. The regular Horse64 language is easier to learn and faster to write, However, any parts written in Horse64 Root can have more lowlevel control and run faster.
See here for the install, and a list of tutorials here. This entire documentation is also included in the Help dialog of the code editor, once you installed it.