Null Piece + refactoring - Implement Chess with Ruby for beginners

In this series, you'll learn how to implement a simple terminal based Chess game with Ruby.

In this episode, we finally talk about the null object pattern and create a NullPiece object that is a singleton for representing the absence of a piece.

Playlist: https://www.youtube.com/playlist?list=PLS6F722u-R6LZxh7mvEUvZKshcH6KSNhr
Code: https://replit.com/@CJAvilla/chess#main.rb