Fore and back (or complementary blinker) is a period-2 oscillator that was found by Achim Flammenkamp in July 1994. Its rotor is the same as the blinker.
Fore and back is about the thirty-eighth most common naturally-occurring oscillator in Achim Flammenkamp's census, being less common than boat on spark coil and block on griddle, about as common as 21P2, and more common than trans-block on long hook eating tub and trans-beacon down on long hook. It is the most common oscillator that is generally agreed to be a billiard table, though some instead give this title to the more common test tube baby, which counts under a looser definition.
In August 2013, a 24-glider synthesis of this oscillator was found by Martin Grant, based on a soup provided by Lewis Patterson. Several days later Mark Niemiec improved this result, having found a 20-glider synthesis.
In October 2014, Tanner Jacobi found a predecessor for this pattern based on a soup from Adam P. Goucher's apgsearch script, which was eventually optimized to a 6-glider synthesis in November.
- 24P2.142 at Heinrich Koenig's Game of Life Object Catalogs