Hopefully it's up to your expectations. Sadly many pieces are still placeholders and my knowledge in game development and programming languages is limited so if you find any mistakes, unclear passages or anything feel free to post about them in the forum board here: https://therealpenaz91.itch.io/2dgd-f0th/community
The book is completely open source, so if someone wants to give a hand making a ruby version, it's more than welcome!