A unit cell is a subset (usually rectangular or square) of the Life plane that tiles over the plane, along with a fixed number of distinct patterns, with each tile assuming one of the patterns, such that it simulates a cellular automaton, possibly itself. A unit Life cell is a unit cell that simulates the Game of Life. To avoid single cells themselves being considered unit cells, the size of a unit cell must be greater than 1x1.
The first unit Life cell was constructed by David Bell in 1996. It employs standard glider logic to determine whether or not a glider should be present. The two states differ by a single glider. In 2004, Jared Prince modified David Bell's unit Life cell to support two (and therefore multiple) layers of Life universes, coined "deep cell".
More recently OTCA metapixel was constructed that simulates any Life-like cellular automaton. Designed to run quickly in HashLife, it has the advantage of having two states that are clearly distinct when zoomed out.
- Paul Callahan (March 1, 1996). "The Unit Life Cell".
- Jared Prince (September 27, 2004). "Game of Life Deep Cell".