Helix Spiral Stairs

Dear forum,

I am trying to create a spiral stairs as seen in the following image.

However, due to the direction of the curve, the stairs have some awkward angles at the top. It is suppose to be flat like normal stairs.

Is there anyway to enable parametric design to create a better looking spiral stairs?

Thank you!

This Grasshopper script might get you started.
The key part is not to use the Z component of the tangent vector.

stair.gh (25.6 KB)