substrate is a PyGame port of J.Tarbell\'s processing visualisation, based upon the xscreensaver implementation by M.Kershaw.Cracks appear and through them sand falls. As the cracks become more numerous a city begins to form. If you continue the disconcerting feeling of moving away will strike you, as the city becomes more dense and continues to evolve.This implementation allows you to place your own cracks and save snapshots.- Parameters you may modify include:- Screen dimensions- Background colour- Crack colour- Sand colours- Initial number of cracks- Maximum cracks- Percentage chance of a crack being curved- Percentage chance of new cracks being connected to old ones- Maximum degrees variation from perpendicular for new cracks- Number of sand grains- Maximum sand rangeRequirements: