It's this shape:
And a couple of instances of them go around a sphere in different directions (the blue dot shows the orientation, which is different from the direction of travel, and the red dot is the centroid):
Far from the center of the projection, they get distorted:
When one wraps around to the other side of the projection it gets all screwy, but I couldn't get a screen cap.
Same repository as last time, now additionally depends on Shapely.