A gentle touch of one of the spikes triggers a noisy chain reaction. The moment of contact is promptly translated into mechanical movements of thirty metal objects. The spikes are retracted at great speed, but sequentially, one after another. After this jumpy reaction, the spike wall halts as if paralyzed. After a while thirty tiny motor engines are set in motion

to push out the spikes slowly and with a crackling noise. Every single object is manufactured in the same way and therefore constitutes a mass of one kind. The contraction of one individual object is passed on to another and therefore creates swarm behaviour.