Quad mesh generation fails

Netgen
1

I am trying to generate quad mesh, but only the triangular mesh is generated.
BIng does not hellp me to solve this problem.
Does anyone know how?

from netgen.csg import Pnt
from netgen.meshing import Element2D, MeshPoint, FaceDescriptor, Mesh
from netgen.webgui import Draw

mesh = Mesh()
#mesh.SetGeometry()
mesh.dim = 2
fd1 = mesh.Add(FaceDescriptor(bc=1,domin=1,surfnr=1))
mesh.SetMaterial(fd1, "Air")
Nx = 3
Ny = 2
v = []
for ny in range(Ny+1):
    for nx in range(Nx+1):
        v.append(mesh.Add(MeshPoint(Pnt(nx,ny, 0))))
for ny in range(Ny):
    for nx in range(Nx):
        mesh.Add(Element2D(fd1, [v[(Nx+1)*(ny+0)+(nx+0)], v[(Nx+1)*(ny+0)+(nx+1)], v[(Nx+1)*(ny+1)+(nx+1)], v[(Nx+1)*(ny+1)+(nx+0)]]))
Draw(mesh)
2

I modified the code and now the mesh is quads.

from netgen.csg import Pnt
from netgen.meshing import Element2D, MeshPoint, FaceDescriptor, Mesh

mesh = Mesh()
#mesh.SetGeometry()
mesh.dim = 2
fd1 = mesh.Add(FaceDescriptor(bc=1,domin=1,surfnr=1))
mesh.SetMaterial(fd1, "Air")
Nx = 3
Ny = 2
v = []
for ny in range(Ny+1):
    for nx in range(Nx+1):
        v.append(mesh.Add(MeshPoint(Pnt(nx,ny, 0))))
for ny in range(Ny):
    for nx in range(Nx):
        mesh.Add(Element2D(fd1, [v[(Nx+1)*(ny+0)+(nx+0)], v[(Nx+1)*(ny+0)+(nx+1)], v[(Nx+1)*(ny+1)+(nx+1)], v[(Nx+1)*(ny+1)+(nx+0)]]))

import ngsolve
from ngsolve.webgui import Draw
mesh = ngsolve.Mesh(mesh)
Draw(mesh)