The chemistry takes places in a discrete, two dimensional, space. Each position in the space is either empty or occupied by a single particle.
Particles generally move in random walks in the space.
L particles may bond to other L particles. Bonded L particles become immobile. An L particle may spontaneously disintegrate, yielding two S particles. When this occurs any bonds associated with the L particle are destroyed also. Chains of L particles are permeable to S particles but impermeable to K and L particles.