Реверси — Стратегия
VOG — Vinco Online Games
Tempo, waiting moves
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Consider Diag. 15. The frontier to the north is equally divided between the two players. It's black to play. He may consider a move to the north (e2, d2, or c2 are reasonable), but of course he would prefer white to play first into this region and lengthen his frontier. This is one of the paradoxical characteristics of Othello: it is often unfavourable to have to move since you flip discs of your opponent and risk giving a number of new moves to your opponent. Now, if black doesn't want to play to the north, the only remaining option is to play to the south. He has the choice between two reasonable moves there: c8 and d7. What will happen if black plays c8? White, who doesn't want to play to the north either, will respond with d7 (Diag. 16), and black must open the game to the north first. By contrast, if black plays d7, the only plausible move to the south for white is c8 to which black may easily respond b8 (see Diag. 17). We say that black has gained a tempo in the southern region. Now it is white who must initiate play to the north. One quick definition of a gain of tempo would be to say that it corresponds to playing one more move than your opponent in a given region of the Othello board (often an edge) and to thus force your opponent to initiate play elsewhere (hence lengthening his frontier). Diag. 18 gives another example of a gain of tempo along an edge. In order to avoid opening the game up to the north, black would like to gain a tempo on the south edge. How can this be done? How should he choose between c8 and f8? One could perhaps believe that these two moves are equivalent with the two sequences c8-f8-g8 (see Diag. 19) and f8-c8-b8 (see Diag. 20). In both cases, black gains the tempo he desired and forces white to be the first to open up the north. However, if we look more closely at the white responses, we see that if black plays c8, white has a better move than f8: he plays g8 ! (see Diag. 21). Now black has no more good moves to the south (if black plays f8, white takes back the edge with b8) and must play to the north: he hasn't gained the tempo he wanted. In the position of Diag. 18, black must therefore play f8 to gain a tempo. Of course, a gain of several tempi is possible. Needless to say in this case your opponent is in even worse shape since then he'll be obliged to play several moves before you are forced to increase your frontier. Diag. 22 gives an example of this. If black plays a7 (see Diag. 23), white has a horrible position. Indeed, white has four reasonable moves: g6, f2, e2 and d2, but he will not be able to play all four. More precisely, he will only be able to play one amongst d2, e2 and f2 since they turn the same black disc; he therefore has, in fact, only two moves. On the other hand, black can gain two tempi on the east edge: he can play a3 followed by a2 ! Diag. 24 gives the position after e2-a3-g6-a2, for example. White is now forced to give up the a8 corner to black. Thanks to his gain of three tempi on the west edge, black has forced white to completely absorb his frontier. Unfortunately, a gain of tempo along the edges often translates into a positional weakness: the player who attempts to gain tempi at all costs will often find himself with particularly dangerous edge configurations (see the chapters on wedges and unbalanced edges). Furthermore, discs on the edges are going to have an influence on future flippings: the player will often be obliged to flip discs in several directions for each move. Thus, in Diag. 25, black has tried to gain tempi by playing on the south and north edges but now that he must play to the west, he is obliged to flip discs in several directions and therefore he is going to end up with more black frontier discs than he would like. |
