Played quite a few games with my wife, winning about as many as I lost. Also had a try at some of the other game modes.
“Y” is more like Columns, in that you have to get lines of three or more rather then groups of gems which you then trigger. It was OK, but not as good as X or X’ modes. “Z” is similar to Hexic, sort of, in that you rotate blocks of four to make groups, that you then destroy with a trigger block. All the time the gems are rising up the screen. This mode was just crap, actually.
Oh, and we stumbled across how to play as Akuma, Devildot and Dan. Dan is, of course, crap. The only gems he dumps on his opponent are red ones, making him easy to beat as he basically provides you with a huge pile of ready-grouped gems. Idiot.