Copyright (c) 2001 Joćo Pedro Neto
After seeing Epaminondas, I associate the stone movements with the idea of 2D shifting. There are another two related operations, namely, rotation and scaling. I took the latter and created SCALUS. Now, after some time, I made KEFREN based on rotation (the original Twirl concept is due to Claude Chaunier inspired in turn by SCALUS). All 3 games have names based on Classical History, and I tend to see my two games as an homage to Epaminondas, forming a kind of 'Classical Trilogy' on abstract games.
KEFREN is played a board with 19x9 intersections. Each player has 18 stones. The initial setup follows:
note: A Twirl is a move by triangulation. The origin, the pivot and the destiny form a triangle, where all cells between the edges are empty. It seems difficult to see Twirls, but after the first game, the idea becomes quite familiar.
Stone G10 can move to E10 using E8 as a Pivot, since both stones are separated by a distance of one cell, and E10 also has a distance of 1 cell both to H10 and to E8. However G10 cannot move to G8, because of stone F8.
Stone C2 can move to G2 using C6 (or C6 can move to G2), but cannot move G6 due to E6. Both C6 and E6 can capture E8 using the other as the Pivot.
A single stone cannot move or capture. KEFREN needs team work to achieve any goal.
The easier way to move is using two stones. The Black walk could go like: B6-B7, C6-C7, B7-B8, C7-C8,... The White walk is three times faster: D10-D7, G10-G7, D7-D4, G7-G4, ....
As expected, as further apart the stones are, the faster is the walk. However, the easier is to prevent that walk from happening (just place some stone between them!)
Some basic tactics
Black moves F3-E4. White must capture. If he moves D4:E4, then C3:E5, and E4 is helpless. If White moves E5:E4, then C5:G9, advancing 4 rows, and D4 cannot move until some other friend comes to the rescue.
Black moves F4-E4. White must capture C4:E4 or C6:E4. Then Black captures two stones with movement F3:E4:E7.
The simple strategy of do not moving the first row of stones does not work! That would mean only half the stones in the center battle, which means that after a while, there will be the remaining enemy army ready to attack that first row, without any reasonable line of defense. In this sample, Black cannot stop the multiple A1, C1 and E1 attack!