const mat2 m = mat2(0.80, 0.60, -0.60, 0.80);

float noise(in vec2 p)
{
	return sin(p.x) * sin(p.y);
}

float fbm4(vec2 p)
{
	float f = 0.0;
	f += 0.5000 * noise(p); p = m * p * 2.02;
	f += 0.2500 * noise(p); p = m * p * 2.03;
	f += 0.1250 * noise(p); p = m * p * 2.01;
	f += 0.0625 * noise(p);
	return f / 0.9375;
}

float fbm6(vec2 p)
{
	float f = 0.0;
	f += 0.500000 * (0.5 + 0.5 * noise(p)); p = m * p * 2.02;
	f += 0.250000 * (0.5 + 0.5 * noise(p)); p = m * p * 2.03;
	f += 0.125000 * (0.5 + 0.5 * noise(p)); p = m * p * 2.01;
	f += 0.062500 * (0.5 + 0.5 * noise(p)); p = m * p * 2.04;
	f += 0.031250 * (0.5 + 0.5 * noise(p)); p = m * p * 2.01;
	f += 0.015625 * (0.5 + 0.5 * noise(p));
	return f / 0.96875;
}

vec2 fbm4_2(vec2 p)
{
	return vec2(fbm4(p), fbm4(p + vec2(7.8)));
}

vec2 fbm6_2(vec2 p)
{
	return vec2(fbm6(p + vec2(16.8)), fbm6(p + vec2(11.5)));
}

float func(vec2 q, out vec4 ron)
{
	q += 0.03 * sin(vec2(0.27, 0.23) * iTime + length(q) * vec2(4.1, 4.3));
	vec2 o = fbm4_2(0.9 * q);
	o += 0.04 * sin(vec2(0.12, 0.14) * iTime + length(o));
	vec2 n = fbm6_2(3.0 * o);
	ron = vec4(o, n);
	float f = 0.5 + 0.5 * fbm4(1.8 * q + 6.0 * n);

	return mix(f, f * f * f * 3.5, f * abs(n.x));
}

void mainImage(out vec4 fragColor, in vec2 fragCoord)
{
	vec2 p = (2.0 * fragCoord - iResolution.xy) / iResolution.y;
	float e = 2.0 / iResolution.y;

	vec4 on = vec4(0.0);
	float f = func(p, on);

	vec3 col = vec3(0.0);
	col = mix( vec3(0.9,0.7,0.1), vec3(0.1,0.5,0.05), f );
	col = mix( col, vec3(0.3,0.3,0.1), dot(on.zw,on.zw) );
	col = mix( col, vec3(0.4,0.3,0.3), 0.2 + 0.5*on.y*on.y );
	col = mix( col, vec3(0.7,0.2,0.1), 0.5*smoothstep(1.2,1.3,abs(on.z)+abs(on.w)) );
	col = clamp( col*f*2.0, 0.0, 1.0 );

	// gpu derivatives - bad quality, butfast
	vec3 nor = normalize(vec3(dFdx(f) * iResolution.x, 6.0,
				  dFdy(f) * iResolution.y));

	vec3 lig = normalize(vec3(0.9, 0.2, -0.4));
	float dif = clamp(0.3 + 0.7 * dot(nor, lig), 0.0, 1.0);
	vec3 lin = vec3(0.70, 0.90, 0.95) * (nor.y * 0.5 + 0.5) + vec3(0.15, 0.10, 0.05) * dif;
	col *= 1.2*lin;
	col = 1.0 - col;
	col = 1.1*col*col;

	fragColor = vec4( col, 1.0 );
}