In a nutshell, this document outlines everything you need to know about game design.
You’ll also learn the best practices and what to do if you don’t understand something.
If you’ve been playing around with Unity for a while, it should be pretty straight forward to follow this guide.
You can download the Concordia Game Design Document as an Adobe PDF document here.
If this sounds like something you’re interested in, here’s a link to the PDF: http://gamedesign.cuny.edu/document/concorde_game_design_document_ultimate_guide_to_making_games.pdf