#https://www.shadertoy.com/view/MdV3Dw

pixels = W:1024 H:1024

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

t = 2.562

angle = atan2(x, y)
radius = length2(x, y)

angle = angle + t - radius*2.5
alpha = 1 - smoothstep(0.5, 1.0, radius)

h = mod(angle/PI*4, 1.0)

r = hsv_r(h, radius, 1.0)*alpha
g = hsv_g(h, radius, 1.0)*alpha
b = hsv_b(h, radius, 1.0)*alpha

