Gutter

The gutter is a single straight line of cells along the axis of symmetry of a mirror-symmetric pattern. Most commonly this is an orthogonal line, and the pattern is then odd-symmetric (as opposed to even-symmetric, where the axis of symmetry follows the boundary between two rows or columns of cells).

The birth rule for Conway's Life trivially implies that if there are no live cells in the gutter of a symmetric pattern, new cells can never be born there. For examples, see 44P5H2V0, 60P5H2V0, Achim's p4, brain, c/6 spaceship, centinal, p54 shuttle, pufferfish, snail, spider, and pulsar (in two orientations).

External links

• Gutter at the Life Lexicon