User:Selinger

Automatic Peep

If Red just completed a bridge and Blue has a bridge peep such that cutting off the bridge would kill the stone Red just played, then Blue should play the bridge peep. This is called an automatic bridge peep. More precisely, if Blue was winning before Red's move, then Blue will still be winning after playing the automatic bridge peep.

For example, consider the following situation, where Red just played at 1:

Because the a-b bridge is bolstered on the b-side, a is a peep. Moreover, if Blue had both a and b, the red stone at 1 would be dead. Therefore, this is an automatic peep and Blue should play at a. (More precisely, if Blue was winning before Red played at 1, then Blue playing at a preserves the win. If Blue was in fact losing before Red played at 1, then Blue playing at a may be losing and Blue may potentially have a winning move elsewhere. In any case, the situation after Blue plays at a is no worse for Blue than before Red played at 1.)

On the other hand, if Blue doesn't play at a, then Red gets away with something that Red shouldn't have been able to do, namely, making a connection without Blue getting a.

There is an analogous notion of automatic peep for ziggurat peeps.