#https://www.shadertoy.com/view/4tSGRm

pixels = W:1024 H:1024

x = from -0.5 to 0.5 W
y = from -0.5 to 0.5 H

radius = sqrt(x*x + y*y)

a = atan2(y, x)
b = 0.2 + 0.1*cos(atan2(x,y)*19.0)

s = radius - b

k = smoothstep(0.1, 1.0 ,pow(s,0.5))

r = 0.9/k
g = 0.2/k
b = 0.05/k

