exciting recreational mathematics: cellular automata. Presentation of a little-known member of their family: the reversible block PLC "Single Rotation".
Some precisions: 5:30 -a random cloud expands. -Only very specific clouds contract. 8:30 The outcome of a collision is not strictly necessarily the emission of a glider, but we do not yet have any example of unbound evolution that is not of this type. And some questions: -Find an unbound evolution that is not of the type of a glider emission. -Find or prove unable oblique gliders (direction other than the main diagonal)