Hello!
Few days ago I start to explore SketchUP with Ruby
And after breaking of my mind with "Google SketchUp Ruby API" and "Automatic SketchUP" by Matthew Scarpino I still have not found an answer - what is the logic of a pushpull method.

What I did.

mod = Sketchup.active_model 
ent = mod.entities
new_circle = ent.add_circle [0,0,0], [0,1,0], 50,3
new_face = ent.add_face new_circle

Here all is clear.
Then

new_face.pushpull 5

OK, face extends to right. And now I have 3D shape.
OK, now I'd like to continue this extension.

new_face.pushpull 5

But now face start to move to left . And if I repeat

new_face.pushpull 5

face will continue to moth to left
So - first pushpull move face to right and next and all another - to left.
What is the logic?

What I need - I'd like to have possibilities to apply pushpull to a particular face after any pushpull. And how to specify for pushpull method exactly that face I need to move?
(And sorry for my English )