From LifeWiki
Jump to navigation Jump to search
8b2o3b$7b2o4b$9bo3b$11b2o$10bo2b2$9bo2bo$b2o5b2o3b$2o5bo5b$2bo4bobo3b$ 4b2o2bo4b$4b2o! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ AUTOSTART ]] #C [[ TRACKLOOP 4 -1/4 -1/4 THUMBSIZE 2 GPS 4 ]]
Pattern type Tagalong
Number of cells 25
Bounding box 13 × 12
Direction Diagonal
Period 4
Mod 2
Speed c/4 | c/4
Heat 22.0
Discovered by Jason Summers
Year of discovery 2000

Crab (or quarter[1]) is a c/4 diagonal 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.

Use as a tubstretcher

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, via a domino spark repeatedly adding units to a tub or long^N barge. Additional non-stretching variants are possible by adding tub-eating c/4 spaceships at the back of the chain(s), at any distance. Such a double wickstretcher was used as the basis for the Speed Demonoid and the self-synthesizing oblique loopship.

8b2o3b$7b2o4b$9bo3b$11b2o$10bo2b2$9bo2bo$b2o5b2o3b$2o5bo5b$2bo4bobo3b$ 4b2o2bo4b$4b2o7b$8bo4b$7bobo3b$8bo! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ THUMBSIZE 2 GPS 2 ]]
The crab as a tubstretcher
(click above to open LifeViewer)
RLE: here Plaintext: here


Main article: List of common spaceships

At 25 cells, the crab is one of the three smallest spaceships yet to appear from soup, alongside 25P3H1V0.1 and 25P3H1V0.2.

Glider synthesis

Martin Grant found a synthesis for crab with the help of Tanner Jacobi and Brett Berger on December 26, 2014.[3] The cost has since been reduced several times, most recently to 14 gliders by Tanner Jacobi on August 16, 2020.[4]

See also


  1. "quarter". The Life Lexicon. Stephen Silver.
  2. New c/4 Diagonal Tubstretcher at Game of Life News. Posted by Heinrich Koenig on August 5, 2005.
  3. Martin Grant (December 26, 2014). Re: How about a crab synthesis? (discussion thread) at the forums
  4. Tanner Jacobi (August 16, 2020). Re: One Glider Seeds (discussion thread) at the forums

External links