mat2 rotate2D(float r)
{
	return mat2(cos(r), sin(r), -sin(r), cos(r));
}

void mainImage(out vec4 fragColor, in vec2 fragCoord)
{
	vec2 uv = (fragCoord.xy - 0.5 * iResolution.xy) / min(iResolution.x, iResolution.y);
	vec3 col = vec3(0);
	float t = iTime * 0.15;

	vec2 n = vec2(0);
	vec2 q = vec2(0);
	vec2 p = uv;
	float d = dot(p, p);
	float S = 20.0;
	float a = 0.0;
	mat2 m = rotate2D(4.0);

	for (int j = 0; j < 20; ++j) {
		p *= m;
		n *= m;
		q = p * S + t * 1.0 + sin(t * 4. - d * 6.) * 0.8 + float(j) + n;
		a += dot(cos(q) / S, vec2(0.2));
		n += sin(q);
		S *= 1.2;
	}

	col = vec3(1.3, 2.5, 4) * (a + 0.3) + a + a + a - (d * 0.5);

	fragColor = vec4(col, 1.0);
}