This link should be updated to https://www.redblobgames.com/pathfinding/a-star/introduction.html https://www.redblobgames.com/pathfinding/a-star/introduction...

This link should be updated to https://www.redblobgames.com/pathfinding/a-star/introduction.html https://www.redblobgames.com/pathfinding/a-star/introduction... which is the updated version of the page which the author links to in the page posted.