Puyo Puyo!! 20th Anniversary (InstanceTopic, 17)
From Compile Worlds
Puyo Puyo!! 20th Anniversary is a Puyo game for the Nintendo DS, released on July 14, 2011.
Most importantly, it brings back Witch as a playable character, and makes Ringo into the most kickass character ever. It features 15 rules, 8 of which are new.
It also features a new 2v2 (team play) mode called "Pair Puyo", where you share trash and "lives" with your partner (a full field thus empties and costs a life). In this mode, you can score bonuses for "Extra Chains" (firing a chain during your teammate's chain) and "Synchro Chains" (firing chains of the same length (3 or longer) at the same time).
Keiji took great pride in being the first to document it on both Puyo Nexus and Wikipedia.