n = 2.5
a = 200
b = 200
glinewidth 0.2
gpenup
while t <= 360
   x = (pow abs cos t (2 / n) * a * sign cos t) / 5 + 50
   y = (pow abs sin t (2 / n) * b * sign sin t) / 5 + 50
   glineto x y
   t += 0.5
.