1. Composition: Full card means that when playing Hu cards, the hand is only composed of ten thousand, stripes (ropes) and drums (cakes) of one suit, which means that the hand is only composed of cards of the same suit, and there are no characters. Mixed color means that there are not only cards (wind cards, wrigley cards or ternary cards) in hand, but also one color among ten thousand cards, strips and cakes, but not all of them are composed of the same color.
2. Calculation of odd numbers: In the national standard mahjong, the odd numbers of various colors are usually high, 24, 6 in front of the door, and 5 in eating, touching and opening. The number of mixed colors is relatively small, which is 6 in the national standard mahjong. In Japanese mahjong, the number of mixed colors will be different because of door cleaning or collision.
3. Strategic difficulty: All cards are required to be the same color, so it is relatively difficult to shape, but it also has a high magic number. Although the number of mixed colors is relatively small, it is relatively easy to form, and because it contains plates, it can increase the possibility of Hu brand.