Swirl

Make a swirl shape with some amount of arms. You can add -TIME directly after float(arms) to make the swirl spin.

float swirl(vec2 uv, float size, int arms)
{
	float angle = atan(-uv.y + 0.5, uv.x - 0.5) ;
	float len = length(uv - vec2(0.5, 0.5));
	
	return sin(len * size + angle * float(arms));
}

void fragment()
{
	float swirl = swirl(UV, 50.0, 6);
	COLOR += vec4(vec3(swirl), 1.0);
}