Narrow Boards
Formation of territory
For some narrow board sizes (such as 2x10), it is not obvious how black can be guaranteed to form a live group (if it is at all possible).
2xN (N large)
Tactical considerations when playing on 2xN boards:
2 x Infinity board
There are three different variations for 2 x Infinity boards: cornerless, 2-corner, and 4-corner, as illustrated below:
The minimal number of stones for a live group with corners is 4. The 4-corner case is equivalent two of 2-corner boards, which can be considered independent since they are separated by an infinite distance.
2 x Infinity with corners
Black's opening options can be analyzed as follows. 1-1 leads to capture.
If black starts with 1-2, 2-4 from white threatens to take the corner. Black 1-5 leads to stalemate. White must respond with 2-5 to avoid being confined to the 4th column (and being left with a bent four). From this point forwards, both players are forced to continue extending their lines indefinitely. Black must continue to avoid being cut off; white unable to hane due to the threat of black forming an L-shape (see Fig. 2.)
If black responds by 2-3, white can reply with 1-5. Black plays 2-6 to threaten white's empty hane. If white starts a fight (First resistance), black wins the capturing race.
But if white completes the 4th column (second resistance), black's mirrored triangle forces white to block black's miai. But now black can capture white.