In spatial computational models such as cellular automata (CA), designing mobile objects larger than the CA neighborhood is challenging when the object properties and dynamics are incompletely specified in advance. This paper introduces C211, a two-dimensional digital ‘protocell’ with life-like and potentially useful features, designed for the best-effort asynchronous CA called the Movable Feast Machine (MFM). The protocell consists of an amorphous variable-density ‘cytoplasm’ that uses gossiping to coordinate operations such as cell movements, surrounded by an asymmetric ‘bilayer membrane’ providing some environmental isolation while adapting to cytoplasmic dynamics. C211 was engineered in a new ‘little language’ called SPLAT, which adds discrete 2D spatial pattern transforms to the ulam programming language. SPLAT is expressive enough that minimal code was required, for example, to enable membrane topology changes such as cell splitting and fusion. C211’s cytoplasm maintains internal state but leaves dozens of bits unused per atom, while its membrane is purely stigmergic and stateless—so vast tracts of pristine CA state space remain available for future cellular dynamics, whether engineered, evolved, or both.

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