This is the solution to Senket puzzle of the week #3.
Red 1 is a promising start, and there are several ways for Blue to respond badly and let Red have territory. In each of the two examples, either B or C makes territory, and Blue can block only one of them.
Blue’s correct response is at 2 shown here, but Blue can still make a mistake. After Red 3, if Blue plays at 4 he secures 9 squares of territory, but after Red 5, both B and C secure territory and Blue can only block one of them. Blue at D takes another 5 squares of territory and leaves Red with 3, for a total loss to Blue of 17 squares.
But proper play after Blue 2 captures. As shown here, after Red 3, Blue 4 secures both 7 squares and Red’s fate. Red 1 is now useless, with no way out, and Red 3 can’t make territory on its own. Blue gains 2 prisoners.
But Red has a way, as shown here. Red 1 threatens to make territory at B. Blue 2 cuts that off. Red 3 threatens to make territory at 4, so Blue 4 blocks. Red 5 delivers the crushing blow. Red can make territory at both C and D, and Blue can prevent only one of them. The end result is likely to be something like that shown below, where Blue 6 and 8 secured 14 squares of territory and a prisoner, along with the 1 point in the corner.
Herman wrote in with a better solution for Red. By going up and to the right with both Red 3 and Red 5, Red can then make territory at 9 or B. Blue can force that decision with Blue 6, taking 5 squares. Red 7 threatens territory at C, which Blue 8 counters. Finally, Red 9 now takes territory. This gains 3 squares of territory for Red, leaving only 10 squares for Blue.
Blue can do better, as shown here. Blue 2 constrains Red from the right side. Red 3 threatens to go underneath, and allows making territory two ways, which is crucial since Blue can cut off Red’s 1 square in the corner at any time. Blue 4 secures 15 squares. Red 5 takes 2 squares. Blue 6 takes 5 squares, and Red 7 takes 1 more. Red ends up with 3 squares, Blue with 20.
Note that after Red 5 all moves are optional, and if either player has a move elsewhere that is worth more he should take it.
I’ll post solutions to the alternative puzzle tomorrow, and a new puzzle.