This is a Mahjong game with Japanese style rules.
Mahjong is a game where you complete 4 tile groups and 1 pair.

Example: [1, 2, 3] [6, 6, 6] [6, 7, 8] [N, N, N] [4, 4]

However, some hands are not approved for Chi, Pon, and Open Kan.
When opening tiles 1 and 9, note that you are holding the hand.
Japanese Mahjong rules require at least one hand.
Hands can also be created by paying 1,000 points and performing Riichi.
However, if you use Chi, Pon, and Open Kan, you cannot run Riichi.
In the case of a closed hand, higher points are obtained.
About Sacred Discard. It is a waiting hand, but if you discard a winning tile yourself, you can not Ron.
If a Riichi player discards a discarded tile, it will never be Ron.
Read your opponent's hand and win.