# OCA:DryLife

DryLife | |

Rulestring | 23/37 B37/S23 |
---|---|

Rule integer | 6280 |

Character | Explosive |

Black/white reversal | B0123478/S0234678 |

**DryLife** is a Life-like cellular automaton in which cells survive from one generation to the next if they have 2 or 3 neighbours, and are born if they have 3 or 7 neighbours. The rule behaves in an explosive manner, as small patterns, such as the stairstep hexomino, may exhibit chaotic growth.

## Patterns

DryLife is so named because the standard spaceships from normal life; lightweight spaceship, middleweight spaceship, and heavyweight spaceship — also known as "fishes" — do not work, though the glider does. Some other spaceships, such as the x66, weekender and loafer, work in this rule. The copperhead evolves into the closely related c/10 *goldenhead*, differing from copperhead by two cells in one phase, and it supports the pseudo-tagalong in fireship as well.

A pair of correctly spaced B-heptominoes (as in the twin bees shuttle) evolves into a messy period-160 c/2 orthogonal puffer.

A new speed allowed by DryLife is 9c/28 orthogonal. Technology travelling at this speed relies on the R-pentomino. Two R-pentominoes constitute a small symmetric 9c/28 orthogonal pond puffer, or a spaceship. A 3-glider collision that synthesises a R-pentomino via beehive works well, so guns and breeders have been constructed that fire spaceships and rakes of this speed respectively.

As for oscillators, there is a small period-32 reflectorless rotating oscillator called spinner, which gives banana sparks and is therefore capable of reflecting gliders by 90 degrees. Jason Summers found that a collision between a glider and a half-open twirling T-tetsons 2 produces two 90-degree gliders while sustaining the pre-pulsar engine, resulting in a period-60 glider gun; a blocker and a spinner can be added as filters for a p480 gun.

The "flower garden", a common constellation composed of two bi-boats and two cis-mirrored buns which evolves from some honey farm predecessors like bun, is shown to the right.

## Universality

There is a proof sketch of DryLife's universality on ConwayLife.com forums. It is a proof-scheme covering all rules in the outer-totalistic rulespace between B3/S23 and B3678/S23678.^{[1]}

In 2018, Peter Naszvadi constructed an explicit Rule 110 unit cell in DryLife, proving its Turing-completeness.^{[2]} The pattern itself is basically a meta-polyglot, covering some related cellular automata in which the pattern only differs in some parts (in this case, the guns).

## References

- ↑ Peter Naszvadi (December 12, 2016). Re: List of the Turing-complete totalistic life-like CA (discussion thread) at the ConwayLife.com forums
- ↑ Peter Naszvadi (March 29, 2018). Re: List of the Turing-complete totalistic life-like CA (discussion thread) at the ConwayLife.com forums

## External links

- DryLife at Adam P. Goucher's Catagolue
- Puffer with unstable trail (B37/S23) (discussion thread) at the ConwayLife.com forums
- Taming B37/S23 (discussion thread) at the ConwayLife.com forums
- DryLife at David Eppstein's Glider Database