http://www.nintendo.co.jp/ds/aykj/index.html?link=txt
Oh yeah, I remember Yakuman back on my original Gameboy! I didn't know how to play Mahjong at the time, though
Default settings don't work for me on the M3, only safe mode does.
Mahjong's actually not hard to play and it's fun! I only read up on it and learned how to play it when I tried out the Gundam Mahjong game on the DS!
All you have to do is try to make your set of "cards" match a certain pattern. There's lots of them but the easiest ones are getting a certain number sequence (eg. 1, 2, 3, 4, 5...) or sets of 2 or more matching "cards". You can learn more about the rules on Wiki:
http://en.wikipedia.org/wiki/Mahjong
One thing to bear in mind however is that the Japanese have a different set of rules than the original Chinese game although they're still similar in ways.
As for this game, yes it's Mario Mahjong basically and the AI's not that hard to beat. I'd say the difficulty is similar to the Gundam Mahjong game I played