Part 7 of this 8 part chess rules course aims to teach about castling. Were other moves already quite unique, castling is in my view at the same time the most exotic and the most vital type of move on the chess board; if one type of move can bring your king to safer areas, it's castling.

The course aims to be a user-friendly, safe, commercial-free and motivating way to learn chess, step by step. Every course part exists of an explanation, followed by exercises. There is no exam, or track of score; it's perfectly ok to make as many errors as needed. Because of random selection of exercises, repetition may occur. Please be patient. Repitition is the mother of skill.

Every part of the chess rules course is a separate app, which has been constructed with NativeScript technology (https://www.nativescript.org/).