Python: goto command : My current assignment asks me to code a graphical representation of some nested squares varying in size from 20-80, like this https://imgur.com/NLt1csa . 
After creating the first square I need to move position to the start of the next square I use the goto command for this. 
My problem is the goto command, I use two variables for the horizontal and vertical inputs but only one of them works at a time, I need them both to work. 
Any help would be appreciated.
(sorry about the formatting, this is my first post)



#Draw a set of nested squares, increasing in size
from turtle import *

number_of_shapes = 4




for shape in range(1, number_of_shapes + 1):
    #Draw a square
    for sides in range(1,5):
        forward(20 + shape * 10)
        right(90)



#Move to position of next square
    penup()
    goto(shape * 10, shape * 10)
    pendown()





