Rotating texture in node mapping make texture gone after rotate more than 90° I am rather new on blender, in this case i was making an eyeball
i want to combine transparent and glossy shader and in the last step i need to rotate the texture to make the transparent side facing front/ the iris but whenever i try to rotate the texture using node mapping color ramp in y axis, 
my texture gone when i rotate it after a certain degree its like having a wrong rotation pivot or something and make me unable to rotate the transparent side reaching the front
here is the screenshot :



blend file : http://pasteall.org/blend/index.php?id=52047

Thankyou and sorry if my explanation isnt clear enough
I think you should rather try with the Texture Coordinate "Object" output, it looks much more controllable than Generated. Here for the manual explanation. Also don't forget to apply the rotation and scale of your object if you want the object axis to be aligned on the global (ctrlA).