python turtle animation (3)

import turtle as t
import colorsys as c
t.tracer(20)
t.setup(1537,865)
w=0
t.bgcolor('black')
t.width(10)
for i in range(2000):
    w+=0.01
    color=c.hsv_to_rgb(w,1,1)
    t.fillcolor(color)
    t.begin_fill()
    t.fd(i)

    t.rt(120)
    t.fd(i)
    t.rt(240)
    t.fd(i)
    t.circle(i,120.1)
    t.end_fill()
t.done()