  We study a Life-like cellular automaton rule $B2/S2345$ where a cell in state
`0' takes state `1' if it has exactly two neighbors in state `1' and the cell
remains in the state `1' if it has between two and five neighbors in state `1.'
This automaton is a discrete analog spatially extended chemical media,
combining both properties of sub-excitable and precipitating chemical media.
When started from random initial configuration B2/S2345 automaton exhibits
chaotic behavior. Configurations with low density of state `1' show emergence
of localized propagating patterns and stationary localizations. We construct
basic logical gates and elementary arithmetical circuits by simulating logical
signals with mobile localizations reaction propagating geometrically restricted
by stationary non-destructible localizations. Values of Boolean variables are
encoded into two types of patterns --- symmetric (False) and asymmetric (True)
patterns --- which compete for the `empty' space when propagate in the
channels. Implementations of logical gates and binary adders are illustrated
explicitly.
