Delta, created by Swiss chess problem composer Erich Brunner, comes with two small boards (one is 5x5 rectangles, the other is 6x6 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 5x5 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 6x6 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.