If I were being pithy, I find that when you're doing this type of thing it's more a feeling of "working fun" rather than "working hard".
(Of course this means that one is probably not always going to do "production ready" things, but it's for fun, so it doesn't really matter. Sometimes it's fun to just go nuts and sprinkle "undefined"[1] all over the code base and just go from types to implementation as fast as humanly possible.)
[1] This is a Haskellism, but basically means any of:
assert(false)
throw new NotImplementedException(...)
???
etc.
(Of course this means that one is probably not always going to do "production ready" things, but it's for fun, so it doesn't really matter. Sometimes it's fun to just go nuts and sprinkle "undefined"[1] all over the code base and just go from types to implementation as fast as humanly possible.)
[1] This is a Haskellism, but basically means any of: