Delta (1975)

Delta, created by Swiss chess problem composer Erich Brunner, comes with two small boards (one is 5×5 rectangles, the other is 6×6 squares), nine triangular pieces in two colors, and one extra piece in a third color.

In Delta, after entering their initial pieces by a free placement, players alternate moving pieces of their own color on the 5×5 board at least two spaces (vertically, horizontally or diagonally), then placing a new piece on the space last passed over by the moving piece. The goal is to create a line of four pieces in your own color or to prevent the other player from being able to move. The winner scores one point for each empty space for making a line or one point for stalemating the opponent. Individual rounds are brief, and several rounds are usually played in a series with the overall winner being the first to reach a pre-determined number of points (such as 100).

Neo-Delta is similar, except it is played on the 6×6 board, and either / both players may use the third color piece (placed by the first player on the first or second move) to form their line of four. Draws are possible.