Kickback reaction/Snippet

The kickback reaction is a collision of two gliders resulting in a single glider travelling in the opposite direction to one of the original gliders. This is important in the proof of the existence of a universal constructor, Bill Gosper's total aperiodic, and many other constructions.

Besides the 90-degree collision shown here, one other two-glider collision with gliders meeting at 180 degrees also produces a clean output glider, and may also be called a "kickback reaction".