Application that draw circles in a loop with varying radius

from kandinsky import *
from math import *
from ion import *

cx = 320 // 2
cy = 222 // 2

x = 0
y = 0
r = 0
vr = 50
t = 0
n = 0
step = 0.01

t = 2*pi
while t < 2*pi:
  set_pixel(cx + round(cos(t) * (r+1)),cy + round(sin(t) * (r+1)),(0,0,0))
  t += 0.001

draw_string("n= " + str(n),0,0)
 
kdown = False
while True:
  if keydown(KEY_UP) and not kdown:
    n += 0.2
    kdown = True
    fill_rect(0,0,320,222,(255,255,255))
    t = 0
    draw_string("n= " + str(n),0,0)
  
  if keydown(KEY_DOWN) and not kdown:
    n -= 0.2
    kdown = True
    fill_rect(0,0,320,222,(255,255,255))
    t = 0
    draw_string("n= " + str(n),0,0)
 
  if not keydown(KEY_DOWN) and not keydown(KEY_UP):
    kdown = False

  if keydown(KEY_BACKSPACE):
    fill_rect(0,0,320,222,(255,255,255))
    draw_string("n= " + str(n),0,0)
    t = 0
 
  x = round(cos(t) * r)
  y = round(sin(t) * r)
  
  c = (abs(sin(t))*255,abs(cos(t*2))*255,abs(cos(sin(t*0.5)))*255)
  #fill_rect(cx, cy, x, y,c)
  #fill_rect(cx, cy, -x, -y,c)
  set_pixel(cx + round(cos(t) * (r+1)),cy + round(sin(t) * (r+1)),c)
  set_pixel(cx - round(cos(t) * (r+1)),cy - round(sin(t) * (r+1)),c)
  set_pixel(cx - round(cos(t) * (r+1)),cy + round(sin(t) * (r+1)),c)
  set_pixel(cx + round(cos(t) * (r+1)),cy - round(sin(t) * (r+1)),c)
  
  r = cos(n*t)*vr
  t += step