What's "riichi-mahjong (Reach Mahjong) ?"

Riichi-mahjong (Reach Mahjong) is of course transformed from China-origin-mahjong but something different as follows:

1. The player who discards the winning tile pays ALL for the winner: so that discarded tiles must be displayed in order.

2. Players must secure at least one hand or "yaku" to declare winning: each player requires a knowledge of yaku. Thirty or more yaku exist.

There are other differences so newbies had a hard time in learnning riichi-mahjong, especially yaku, until datsui-mahjong, or arcade strip mahjong game appeared in early 1980s.