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The first known gun, the Gosper glider gun

A gun is a stationary pattern that repeatedly emits spaceships (or rakes) forever. By far the most common type of guns are glider guns, which emit gliders (the most well-known of which is the Gosper glider gun); however, guns that emit spaceships of many other speeds, including c/2 orthogonal, 2c/5 orthogonal, and c/12 diagonal, have also been created.


The first gun to be discovered, the Gosper glider gun, was found by Bill Gosper in 1970, being the first known pattern in Conway's Game of Life to exhibit infinite growth. Since then, many guns have been constructed with various periods and that fire spaceships of various speeds. Due to simple glider syntheses of the standard spaceships many c/2 spaceship guns are known. The first gun that did not fire gliders or c/2 spaceships was a Cordergun (a gun that fires Corderships) constructed by Jason Summers in July, 1999[1] based on a synthesis of a variation of the 7-engine Cordership by Stephen Silver. In March, 2003 Noam Elkies completed the synthesis of 60P5H2V0 which Dave Greene used to construct the first 2c/5 spaceship gun in April of the same year.

In July, 2010 Dave Greene constructed a few guns for a geminoid spaceship.[2] These are the first guns that shoot obliquely-traveling spaceships and at that time were the largest patterns constructed in Life, in terms of their bounding boxes.

On February 17, 2013 Josh Ball discovered a simple c/7 orthogonal spaceship, loafer. Adam P. Goucher found a synthesis for the loafer later that day, allowing the construction of c/7 orthogonal spaceship guns.[3]

During March 2016 the copperhead spaceship was discovered, with a glider synthesis and several guns following suit.[4]

In 2019 and 2020 guns were produced for the spaceships 46P4H1V0,[5] spider,[6] and 58P5H1V1,[7] of speeds c/4 orthogonal, c/5 orthogonal, and c/5 diagonal respectively.


Main article: Barrel

The barrel of a gun (or rake) is a path along which spaceships travel. For example, a double-barrelled glider gun is a gun that emits two glider streams.

Pseudo-period guns

A pseudo-period gun (as opposed to a true-period gun) is a gun that emits a period n stream of spaceships (or rakes) via a mechanism that oscillates with a period different from n -- this period will necessarily be a multiple of n. Pseudo period n glider guns are known to exist for all periods greater than or equal to 14, with smaller periods being impossible. The first pseudo period 14 gun was built by Dietrich Leithner in 1995.

True-period guns

A true-period gun (as opposed to a pseudo-period gun) is a gun that emits a period n stream of spaceships (or rakes) via a mechanism that oscillates with period equal to n. True period n guns are known to exist for all possible periods except for 14, 17, 18, 19, 23, 26, 29, 31, 35, 38, 39, and 47. Credits for gun periods below 62 are as follows:

Period Discoverer Year of discovery
15 Period1GliderGun and Carson Cheng 2024
16 Period1GliderGun and Nico Brown 2024
20 Matthias Merzenich and Noam Elkies 2013
21 Tanner Jacobi and David Raucci 2021
22 David Eppstein and Jason Summers 2000
24 Noam Elkies 1997
25 Mitchell Riley 2022
27 David Raucci and goldenratio 2022
28 Matthias Merzenich and Paul Callahan 2020
30 Bill Gosper 1970
32 Matthias Merzenich, David Raucci, praosylen, wwei23, and Noam Elkies 2021
33 Arie Paap and Matthias Merzenich 2018
34 Nico Brown 2022
36 Jason Summers 2004
37 iNoMed, goldenratio, and Luke Kiernan 2022
40 Adam P. Goucher, Jason Summers, and Matthias Merzenich 2013
41 iNoMed, Matthias Merzenich, May13, David Raucci, and Nico Brown 2023
42 Tanner Jacobi and David Raucci 2021
43 Nico Brown 2022
44 David Buckingham 1992
45 Matthias Merzenich 2010
46 Bill Gosper 1971
48 Noam Elkies 1997
49 Tanner Jacobi, wwei23, and hotcrystal0 2021
50 Dean Hickerson and Noam Elkies 1996
51 Luka Okanishi, wwei23, and hotcrystal0 2021
52 Dave Greene, Chris Cain, Matthias Merzenich and Adam P. Goucher 2018
53 iNoMed and goldenratio 2024
54 Dietrich Leithner 1998
55 Stephen Silver 1998
56 Dietrich Leithner 1998
57 Matthias Merzenich 2016
58 Maia Karpovich, Matthias Merzenich, and Chris Cain 2016
59 Adam P. Goucher and Jason Summers 2009
60 Bill Gosper 1970
61 Luka Okanishi 2016

Smallest guns by area of bounding box

A collection of smallest guns by bounding box area was originally created and maintained by Dietrich Leithner and Peter Rott, before Jason Summers took over the maintenance. The p14-999 collection had subsequently evolved into a Git repository led by Chris Cain. Currently, the collection is maintained collaboratively at Catagolue's glider-synthesis database.

Note that this classification of smallest is of dubious utility: see Pointless optimisation game for more details.

Guns in Life-like cellular automata

Due to the existence of some small spaceships in Life-like cellular automata with birth at two live neighbours (B2), many low-period spaceship guns have been found using tools such as WinLifeSearch. In contrast, there are very few outer-totalistic rules without B2 (and B0) that are known to contain guns. The following is a list of outer-totalistic rules with neither B0 nor B2 that have known guns:

See also


  1. "Game of Life Status page". Retrieved on October 15, 2010.
  2. Gemini guns at Game of Life News. Posted by Adam P. Goucher on July 30, 2010.
  3. Shannon Omick (February 18, 2013). Re: c/7 orthogonal spaceships (discussion thread) at the forums
  4. Alexey Nigin (March 6, 2016). Re: is this c/10 spaceship known? (discussion thread) at the forums
  5. Goldtiger997 (October 22, 2019). Re: Stable signal converters (discussion thread) at the forums
  6. Entity Valkyrie (January 26, 2020). Re: Small Spaceship Syntheses (discussion thread) at the forums
  7. Entity Valkyrie (May 22, 2020). Re: Construction practice (discussion thread) at the forums
  8. Matthias Merzenich (April 11, 2013). Guns in Life-like cellular automata (discussion thread) at the forums

External links