In the previous topic, we met with the debut regulations, it’s time to get acquainted with the debuts themselves. In Renju, as in any other similar game, there is a debut theory. But before touching it, let’s first get acquainted with the debuts themselves and calculate how many of them there are. How to do it?
Debut in Renju is called the first three moves (in a broader sense, the debut stage lasts longer). To calculate the number of debuts, we need to know how many options there are for the first three moves, but at the same time, we should not forget about the symmetric moves that should be eliminated. So, let us remember what restrictions exist for the first moves: the first move is necessarily made only to the center, that is, there is only one point for it. The second move can be squared 3 * 3, i.e. for it there are 3 * 3-1 = 8 fields. However, how many of them are asymmetrical?

Possible second moves

It is easy to verify that all vertical and horizontal (highlighted in blue) possible second moves, as well as all diagonal (highlighted in red) are symmetrical to each other. It turns out that there are two principled asymmetrical second turns – vertical (or horizontal) and diagonal. Therefore, all debuts in Renju can be divided on the second move into vertical and diagonal ones.

For the third move there is 5 * 5-2 = 23 points, however, it will be more difficult to remove symmetrical ones.

Possible third moves

The green line marks the axis of symmetry: all third moves that are on the same side are completely identical to the third moves that are on the other side (the symmetric third moves are highlighted in green). On each side there are 10 asymmetrical strokes + 3 on the axis of symmetry (which have no symmetrical ones). It turns out that there are only 26 openings in Renju: 13 vertical and 13 diagonal. Now it is worth saying a few words about how the debuts are called. In Renju it is not customary to call debuts by the names of famous masters practicing them (if only because there are quite a few openings, only 26), although sometimes you can find some fancy names for specific options (Glukhovsky gambit, Moscow region, turtle, little chest, etc. ).

In Renju, as already mentioned above, the openings on the second move are divided into vertical and horizontal, and on the third move, each opening has its own number, they are named like this: first vertical, second vertical, first diagonal, second diagonal, etc. In the krtak annotation, openings are usually denoted 1B, 2B, 1D, 2D. To find out what debut is in front of you, you need to build a traffic light and then count the sequence number of the third move from left to right (for vertical debuts) and from top to bottom (for diagonal ones).

Numbering debuts in Renju, circled in red first debuts – traffic lights

There is a small classification of debuts under the RIF regulations for a beginner. In all knight debuts (the third move is located by the letter “g” from the first), and also in 4v / 7d there is an advantage of black, in all debuts, where the third stone stands diagonally through the cell from the first – the advantage of whites. In all other openings, a game with two alternative fifths is either optimally drawn, or with a very hard-to-implement black win.

In this thread, you learned:
How many debuts are there in Renju;
What are the debuts called?
What debuts are rated for black. and which whites are reef under the rules.