player1.pendown()
        player1.forward(50)
        player2.pendown()
        player2.forward(50)

def advance_state_machine():
    global state_num
    if state_num == 0:
        tess.forward(70)
        tess.fillcolor("red")
        state_num = 1
    else:
        tess.back(70)
        tess.fillcolor("green")
        state_num = 0
        player1.pendown()
        player1.forward(50)
        player2.pendown()
        player2.forward(50)


    wn.onkey(advance_state_machine, "space")

wn.listen()
wn.mainloop()