It's not a tutorial, but Ridiculous Fish wrote about his experience writing Hex Fiend (https://www.google.com/&q=site:ridiculousfish.com%2Fblog+%22hex+fiend%22

It's not a tutorial, but Ridiculous Fish wrote about his experience writing Hex Fiend (https://www.google.com/&q=site:ridiculousfish.com%2Fblog+%22hex+fiend%22 https://www.google.com/&q=site:ridiculousfish.com%2Fblog+%22... ); see, for example, http://ridiculousfish.com/blog/posts/old-age-and-treachery.html http://ridiculousfish.com/blog/posts/old-age-and-treachery.h... .