CHAOS;JAN is a new rule set, inspired by Magic: The Gathering Planechase, to sow chaos onto the Mahjong table. It adds a deck of 30 cards which either modify the rules or trigger an event. These effects range from stripping dragons of their value, to making the game play with Aotenjou scoring.
To draw a new card, a player may—before they draw a tile—pay 1,000 points to roll a die. If that die rolls onto an odd number, they draw a card. If they roll an even number, nothing happens. If a player wants to roll again, they'll have to pay twice as much as before, with the cost to roll reseting back to 1,000 at the start of each hand. Players can only roll once per turn, however, and may not roll after calling pon, kan, or chii.
Modifier cards change the rules of the game. There can only be one modifier active at a time, and is replaced if another modifier is drawn. Modifiers can change how chii works, or add a new call, or even strip the game of mangan limits.
Event cards makes something happen once or starts an event when they are revealed. Any number of events may be active at once, including swapping tiles with opponents, swapping tiles with your own discards, or allowing players to take a couple of points, just for discarding the last tile in the wall. Some events occur instantly, while others linger for the rest of the hand.
Ready to play? Click the link below to access the Cosmic Deck. It'll draw a card when the page loads, and keeps track of the active modifier for you. If you want to make sure you're playing the game correctly, check the Full Rules page once it's ready, or find the rulings for specific cards on the All Cards page.