There are several related games, which can be considered as a variation of the same game. All of them are Solitaire game using a standard set of 32 tiles. Classic triplets are used in the game.
The first game is Guo Wu Guan (過五關), Passing Five Levels. The tiles are laid out in seven rows. The top row is a row of generals, six tiles are placed there, only the outer ones can be used, so the rest are opened during the game. Then five rows of five tiles are placed – that’s five levels, and one remaining tile is placed in the seventh row, which is called common.
Each move consists of three phases:
- Starting from the top, the player takes three adjacent tiles from each level if they form a correct triplet. Moreover, the leftmost and rightmost tiles are considered adjacent. Adjacent tiles can be located both in the middle of the level and from the edge (or from the edges). Any triplet found in this way is added to the common (bottom) row on the left. If there are no tiles left in the level at this stage, it still remains in play.
- If in any level there are exactly two tiles left that form a triplet with one of the extreme generals, that is, the left or right tile of a row of generals, then this general is considered killed and this triplet is also placed in the common row on the left. The level is considered passed and no longer participates in the game. Once per game, there should be a situation where a triplet is formed by a single level tile and two open generals. There are six generals, and five levels, so one kill of a general should be a double kill.
- Tiles on the right side of the common row are added from the right to all levels still in the game, starting with the lowest one. It may happen that there will be more levels than tiles in a common row, so higher levels may not get tiles at this stage. Please note – sometimes it may happen that the row is empty, but not passed, so during this stage a domino may be added to an empty row.
The game is won if all six generals are killed and five levels are completed. The game is lost when there are no tiles left in the common row and no triplet can be formed.
Rule variations
There are several variants of this game. First, to begin with, you can remove the restriction that the tiles forming the triplet must necessarily be adjacent. In this way, a triplet can be formed by any three tiles from a level. This gives more chances to win, although it will take a little longer to search for triplets.
A similar game was once played in Korea, and if to believe Culin, it was a very common pastime among intellectuals, something like modern crossword puzzles. The game was named O-Koan and was played almost identically with the following differences: in five levels at the beginning only four tiles were laid out, the remaining twelve tiles formed a common row. The row of generals did not exist so the second phase also did not exist, and the level was considered completed when there were simply no tiles left in it.
The advantage of the O-Koan game is that there you can abandon the relatively inconvenient search for triplets inside the level, since at the beginning of the game all the tiles are external (there are only four of them), and in the future, if a triplet is in the middle, it is only because that the player had not noticed it before.
In modern times, a game almost identical to O-Koan is played, which is called Clear Five Levels (通五关), except that there are two tiles in a common row, and at the start of the game there are six tiles in each level instead of four.
There is also a variant of Seven Captures of Meng Ho (七擒孟言). In this variant, the general is always a [2:1] tile named Meng Ho. There are seven levels with three tiles each, there are ten tiles in a common row at the beginning. Whenever a general is captured, he falls into the common row as always, but when it comes time to add him to one of the already existing levels, he jumps back into the general row – like escaping from prison. Since there are seven levels, Meng Ho must also be captured seven times. Hence the name. Meng Ho is a historical figure who is said to have been captured seven times during his war because of his self-confidence.
Sources
Rules description on Pagat
O-Koan description by Culin
Rules description on Chinese Wikipedia
Chinese Dominoes GuPai 