pixels = W:1024 H:1024

x = from -1 to 1 W
y = from -1 to 1 H

a = 0.4
b = 0.2
c = 0.5
u = sqrt((x - a)*(x - a) + y*y)
v = sqrt((x + a)*(x + a) + y*y)

k = 2.0 - smoothstep(b,c,u) - smoothstep(b,c,v)

r = 1.0 - k
g = r
b = r
