Rotating Two Perpendicular Lines Scapes

[TVsVeryOwn]

I've got a 3D grid with the Line Scapes. I want to rotate the direction of both the horizontal and vertical to change on one fader with the grid staying sort of in square
I've never been very good at geometry, but I'm pretty sure I need to make sure there's always a 90 degree difference between the two. What do I have to make my envelope do?

[TVsVeryOwn]

Solved it. It was as I suspected and I just had to make an envelope subtracting 90 degrees, but since the scale doesn't go below -180 degrees I had to flatten the envelope for both and X and Y at 25%.