This acid is male and female again and can only move over threshold acceptable ground, they also project their beings on to an image in memory so they can't pass over each other. They constantly look around them for the easiest ground to convert to threshold and change it. I originally programmed them to travel until trapped but they just wigged on the spot after making a small nook of open ground. Now they flow like some strange sand, piling up in areas of contrast. The image is of a demolition in progress at East India DLR station.
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