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6bobob$5bo4b$2o2bo4bo$2obo2bob2o$4b2o! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ AUTOSTART ]] #C [[ GPS 4 THUMBSIZE 2 ]]
Pattern type Oscillator
Number of cells 15
Bounding box 10 × 5
Frequency class 27.2
Period 8
Mod 4
Heat 9
Volatility 0.89
Strict volatility 0.89
Discovered by Robert Wainwright
Year of discovery Unknown

Blocker is a period-8 oscillator found by Robert Wainwright.[1] It consists of two blocks hassling an unnamed object which is a dying spark. It reappears halfway through its cycle rotated 180°.

Blockers can also be infinitely connected by "sharing" blocks, as long as adjacent reactions are no more than one phase apart. They can also be connected with Coe's p8, which uses blocks as catalysts in a similar manner.

x = 18, y = 12, rule = B3/S23 6bobo5bobo$5bo7bo$2o2bo4bo2bo4bo$2obo2bob2obo2bob2o$4b2o6b2o3$14bobo$ 5bo7bo$3ob2o2b2o2bo4bo$4o4b2obo2bob2o$4b2o6b2o! #C [[ THUMBSIZE 2 THEME 6 GRID GRIDMAJOR 0 SUPPRESS THUMBLAUNCH ]] #C [[ AUTOSTART GPS 4 ZOOM 16 HEIGHT 400 THUMBLAUNCH THUMBSIZE 2 LOOP 8 ]]
Blockers sharing blocks
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RLE: here Plaintext: here


Blocker is a versatile corner dot sparker employed in many situations, for example two pre-L hasslers, p40 and p56 B-heptomino shuttle, and two blockers hassling R-pentomino.

As a filter, a blocker can double the period of a glider stream that is a multiple of 4 but not 8 by deleting every second glider.


Main article: List of common oscillators

Blocker is about the sixteenth most common naturally-occurring oscillator in Achim Flammenkamp's census, being less common than mazing but more common than jam.[2] On Catagolue, it is the second most common period 8 oscillator, being less common than the figure eight but more common than Coe's p8.[3]

The first natural blocker stator variant, blocker on cap, occurred in September 2015.[4]

Glider synthesis

In January 2015, Bob Shemyakin found a two-stage 5-glider synthesis of a blocker.[5] Another two-directional 5-glider recipe was used in a larger synthesis in 2022.[6]

See also


  1. Dean Hickerson's oscillator stamp collection. Retrieved on March 14, 2020.
  2. Achim Flammenkamp (September 7, 2004). "Most seen natural occurring ash objects in Game of Life". Retrieved on January 15, 2009.
  3. Adam P. Goucher. "Statistics". Catagolue. Retrieved on October 27, 2018.
  4. Billabob (September 9, 2015). Re: Soup search results (discussion thread) at the forums
  5. Bob Shemyakin (January 7, 2015). Re: 4 glider syntheses (discussion thread) at the forums
  6. Ian07 (February 21, 2022). Re: Synthesising Oscillators (discussion thread) at the forums

External links