Pentalath (also called Ndengrod) is an abstract board game for two players, designed by a computer program called LUDI, invented by Cameron Browne.
It is the "brother" of Yavalath and it can be played using a Yavalath set.
It is available from nestorgames.
Rules
Players: White and Black.
Start: The board is initially empty.
Play: Players take turns placing a piece of their colour at an empty cell. After each move, any same-coloured groups with no freedom (i.e. no adjacent empty board cell) are captured and removed.
End: Players win by making a line of five or more pieces of their colour.
First move equaliser: The second player has the option of swapping colours in lieu of making the second move. This stops the first player from making too strong (i.e. central) an opening move.