The Courant-Friedrich-Lewy condition
Or: you have to step before you can run.
(at a rate of less than 1 space unit per time unit)
The region sketched out in green should then correspond to areas that satisfy the CFL condition.
I think you'll agree there is some deviation between the region that supports the glider (bounded in black) and the region sketched out for the CFL condtion (in green).
