A shearline (also called windshear) is a generalized term for when two different air masses contact each other with motion relative to one another. This motion might be with one sliding past the other or where one converges against the other. The converging situation is often called a "convergence". The drawing below shows how a southwest wind meets a northwest wind over the area to the east of Elsinore. The resulting convergence provides abundant thermals for good soaring conditions. It is Elsinore's unique though shortlived daily presence of a shearline that the Hangfly game uses to set up its soaring simulation.