Day & Night

Explorer rule · B3,6-8/S3-4,6-8

Symmetric between alive and dead.

Day & Night in the 3D Game of Life: cells as cubes in a 15×15×15 box, 40 generations in. — After 40 generations from a random fill with 50% of cells alive, in a 15×15×15 box that wraps at its edges: 972 live cells.

How the rule works

Each cell has 26 neighbours: every cell that shares a face, an edge or a corner with it (the Moore neighbourhood).
An empty cell comes alive when 3 or 6 to 8 of its neighbours are alive.
A live cell stays alive when 3, 4 or 6 to 8 of its neighbours are alive; otherwise it dies.

Picking it in the app restarts the world from a random fill with 50% of cells alive. Its seed is fixed, so it is the same world every time, one still alive 40 generations later in the default 15×15×15 box; N tries another seed.

Notation

Birth/survival	`B3,6-8/S3-4,6-8`
Softology, MCell (S/B/C/N)	`3-4,6-8/3,6-8/2/M`
Weighted counting	`B9,16-18/S9-12,16-18` (faces count 3, edges 2, corners 1)
Neighbourhood	Moore (26 cells)

B lists the neighbour counts at which an empty cell is born, S those at which a live cell survives, and C the number of states. How to read a rule

More explorer rules

2D Conway B3/S2-3
Life 4555 B5/S4-5
Spiky B4-6/S5
Seeds B3/S
Maze B3/S1-5
Explosive B4-5/S3-4
Life 5766 B6/S5-7

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