If you’re anywhere near up to speed in Hunter x Hunter, there’s a decent chance you’ve heard of gungi. During a very intense portion of the narrative, the game becomes a pivotal piece on the storyboard; however, all we really learn about gungi is that it’s a chess-variant in which you can stack pieces on one another. The rules are left unexplored by Togashi, and fans in the English-speaking HxH community are left alone in a dark continent. Lucky for us, the fans in Japan are on top of things.
Turns out that fans have already sorted out and laid down functional rules for gungi across a series of forum threads! WHOA! A Japanese blogger going by Nishitsuji Sannkurou extensively covered instructions for gungi in this post; I translated it for personal reference and will now confer the rules to you.