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Backgammon is a purely strategic chess game played by two people. Usually, both sides use black and white chess pieces and place them at the intersection of the straight and horizontal lines on the chessboard. The first one to connect 5 pieces wins. Do you know about Gobang? Forbidden hands? Below is the knowledge about forbidden hands in backgammon. Welcome to read it.
①What is the forbidden hand in backgammon?
As the name suggests, forbidden hands are points on the chessboard where chess is prohibited.
The forbidden hand is set for black. White has no forbidden hand restrictions.
②What are the banned players in backgammon?
The most basic types of forbidden hands include three kinds: double active three forbidden hands, double four forbidden hands, and long continuous forbidden hands.
Double live three forbidden hands: When a chess piece falls, the piece forms two or more live threes on the chessboard at the same time, then this point is the double live three forbidden hand point.
Figure 3-1
As shown in Figure 3-1, the red cross point is the most common dual-active and three-ban hand point.
In addition, the red cross points in the two pictures below are common dual-active and three-ban hand points. Of course, there are many different shapes besides this, so I won’t list them all here.
Figure 3-2
Figure 3-3
In addition, let me mention this a little bit. In the situation shown in Figure 3-4 below, it is easy to confuse the three. The three in the vertical line is actually a sleeping three (I mentioned it when I introduced the sleeping three pattern above. I don’t understand. Students can review it). Therefore, point A is not dual-active and three-banned.
Figure 3-4
Double Four Forbidden Hands: When a chess piece falls, and the piece simultaneously forms two or more living fours or flush fours on the chessboard, then this point is the Double Four Forbidden Hands point.
Figure 3-5
As shown in Figure 3-5, it is the most common double-four forbidden point. It needs to be explained here that the four in double four includes living four and rushing four. Any combination of the two will form a double four forbidden hand. I will not give examples one by one here.
Long-term forbidden hand: A chess piece falls, and the piece forms a chess pattern with 6 or more black chess connected together on the chessboard, then this point is the long-term forbidden hand point.
Figure 3-6
As shown in Figure 3-6, this is the most common form of long-term hand ban. Similarly, the form of long-term hand ban is not the only one. There are other forms, which will not be listed here.
③What should you pay attention to when banning hands?
1. Simultaneity must be formed at the same time.
Figure 3-7
As shown in Figure 3-7, when Black moves three at 1, White jumps 2 and rushes to four, forcing Black to move at 3. Then it is wrong to accuse Black of forming a double move and three forbidden moves. Because the live threes of vertical lines and the live threes of horizontal lines are not formed at the same time, but are formed one after another.
2. Identicality must be formed by the chess piece just dropped.
Figure 3-8
Figure 3-9
As shown in Figure 3-8, when Black rushes to the four at position 1, an open three is first formed on the diagonal;
Secondly, at the same moment, the three on the horizontal line that originally turned into Mian Three due to the four-four forbidden hand at position 2 (see Figure 3-9, the three on the horizontal line in the picture is Mian Three. According to Mian The definition of three, at this time, the three on the horizontal line can only form a four, so it is a sleeping three), but due to the existence of black 1, it becomes a living three (because at this time, a living four can be formed at the position of 2, according to The fixed formula of living three, the three on this horizontal line is living three);
So at this time, White accuses Black of forming two live threes at the same time. Is it a double live three banning pair?
It's obviously wrong. Because although the principle of simultaneity is not violated at this time, it does violate the principle of homogeneity. The diagonal threes and the horizontal threes are not both composed of black 1.
3. Timeliness. If a forbidden hand appears, it must be pointed out in time. It will be invalid after expiration.
Figure 3-10
As shown in Figure 3-10, when Black's 11 fell, a forbidden hand originally appeared on the chessboard, but because the student holding White did not notice it at the time, he dropped White 12. After falling, he suddenly discovered that Black had just The chess piece was blocked. At this time, he accused Black of having just 11 double live and 3 forbidden hands. This is wrong, because when you play 12, it has been defaulted to allow black to play double live three and banned hands, so the banned hand becomes invalid. At this time, black can continue to change live three into live four.
4. Multiplicity, which is relatively complicated. Please see the introduction of multiple hand bans below for details.
5. Five in a row is the largest. On the chessboard, if five in a row and a forbidden hand appear at the same time, then the forbidden hand will be invalid and five in a row will win.
Figure 3-11
As shown in Figure 3-11, Black's chess is at point A. Although it seems that there is a long horizontal line shape, due to the chess shape on the vertical line, there happens to be a straight five after point A. Then after the move at point A, the horizontal line The long sequence above was invalidated due to the vertical line of five consecutive pieces, and Black's five consecutive pieces were awarded as the winner.
④About the multiplicity of forbidden hands
Figure 3-12
Figure 3-13
As shown in Figure 3-12, the black piece falls at 1, forming two threes in horizontal and vertical lines. Many students may think that 1 is a double-active three-forbidden point. So, is this point a forbidden point? What? How to judge?
If you want to judge whether a place is a forbidden point, you need to accurately understand the definition of forbidden points. Because the dual-active and three-banned hands are involved here, let’s first take a look at what the dual-active and three-banned hands are.
Double live three forbidden hands: When a chess piece falls, the piece forms two or more live threes on the chessboard at the same time, then this point is the double live three forbidden hand point.
According to the definition above, we can know from a simple analysis that the most important thing here is to determine whether the two threes on the horizontal and vertical lines after a move are live threes.
For the three on the horizontal line, since it can form a live four at point A or B, according to the definition of live three (the three that can form a live four is called a live three), we can judge that the three on the horizontal line is a live three.
For the three on the vertical line, at the position of 2, we could originally form a living four chess pattern. However, on the horizontal line where 2 is located, there happens to be a sleeping three chess pattern, and among the three sleeping chess patterns are One hits four points, which is exactly where 2 is. What does this mean?
This means that the position of 2, as shown in Figure 3-13, will become the four-four forbidden point. This also means that the three on the vertical line cannot form a free four at the 2 position, but can only be placed at the 3 or 4 position to form a rushing four pattern. According to the definition of sleeping three (the three that can only form a rushing four is called sleeping) Three), we can judge that the three on the vertical line is sleep three.
To sum up the above analysis, we can know that after the black piece was placed at 1 point, a horizontal three and a vertical three were formed, that is, two living threes were not formed. Then we can conclude that there is no forbidden position at 1. Hands on.
Through this question, we can see that when there is multiplicity of forbidden hands on the chessboard (as shown in the example in Figure 3-12), judging the forbidden hand at 1 needs to take into account the judgment of forbidden hands at 2 places in the next layer. Here, there is We generally describe the situation as "four-four resolves three-three", that is, the forbidden hand 4-4 at 2 removes the forbidden hand 3-3 at 1, so that 1 is no longer a forbidden point.) The judgment of forbidden hand is actually not It's not as simple as it seems. The hand-banning judgment of each layer is affected by the hand-banning judgment of the layer below.
The example given above is the simplest case of multi-layer hand ban. If you delve into it in depth, it will be more complicated. However, as a beginner, you don’t need to touch it for the time being. After all, complex multi-layer hand bans are very important in games or ordinary confrontations. The probability of it appearing in the game is very small.
