From Mr. de Bono's website:
The intention was to produce the simplest possible game that could be played with a high degree of skill. An attempt was made to fulfill the following conditions:
1. A minimum number of playing pieces, preferably one each.
The smallest possible board.
2. A game with very few rules, one that would be very simple to learn and play.
3. A game that could be played with a high degree of skill.
4. A game that would not be determinate. A determinate game such as nim or noughts and crosses, is one in which the starting player could always win if he knew the strategy. An indeterminate game is one which two perfect players would play for ever.
The object is to score 12 points provided that the other player scores at least 6 points - if the other player scores less than six points then the player reaching 12 points is the loser! Whereas in most games the person scoring the highest number of points is the winner - in the 3 Spot game the 'winner' can be the 'loser'.
Points are scored by the position of the tiles on the board which is a 3x3 grid. You can try to score the points you need, or force your opponent to take points.
Appears with L-Game in Rex Games' Two Smart Games mini-anthology.