:x66 (c/2 orthogonally, p4) Found by Hartmut Holzwart, July 1992. Half of this can be escorted by a HWSS. The name refers to the fact that every cell (live or dead) has at most 6 live neighbours (in contrast to spaceships based on LWSS, MWSS or HWSS). In fact this spaceship was found by a search with this restriction.
..O...... OO....... O..OOO..O O....OOO. .OOO..OO. ......... .OOO..OO. O....OOO. O..OOO..O OO....... ..O......
:Xlife A popular freeware Life program that runs under the X Window System. The main Life code was written by Jon Bennett, and the X code by Chuck Silvers.
:X-pentomino Conway's name for the following pentomino, a traffic light predecessor.
.O. OOO .O.