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8b2o3b$7b2o4b$9bo3b$11b2o$10bo2b2$9bo2bo$b2o5b2o3b$2o5bo5b$2bo4bobo3b$ 4b2o2bo4b$4b2o! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ AUTOSTART ]]
Pattern type Spaceship
Number of cells 25
Bounding box 13×12
Direction Diagonal
Period 4
Mod Unknown
Speed c/4
Speed (unsimplified) Unknown
Heat 22.0
Discovered by Jason Summers
Year of discovery 2000

Crab (or quarter[1]) is a diagonal c/4 spaceship that was found by Jason Summers in September 2000. It is the smallest known diagonal spaceship other than the glider and it consists of two gliders pulling a tagalong.

It was noticed by Nicolay Beluchenko in August 2005 that it can be converted into a small tubstretcher, as shown below.[2] This tubstretcher is the basis for the one per generation pattern.

Due to the diagonal glide symmetry and by simple inspection, the spaceship can easily be made to stretch two tub wicks simultaneously. Both cases are instances of a domino dragging a tub or chain of tubs. Be it noted that tub chains are also called barges, and that additional non-stretching variants are possible given synchronized eating at the far ends.

Martin Grant found a synthesis for crab with the help of Tanner Jacobi and Brett Berger on December 26, 2014.[3]

Image gallery

The crab as a tubstretcher.
RLE: here

See also


  1. "quarter". The Life Lexicon. Stephen Silver.
  2. H. Koenig (August 5, 2005). "New c/4 Diagonal Tubstretcher". Game of Life News. Retrieved on May 9, 2009.
  3. Martin Grant (December 26, 2014). "Re: How about a crab synthesis?". Retrieved on December 26, 2014.