// A trippy zooming feedback plasma I first made at http://glslsandbox.com/e#45069.2 (I just mention this to avoid someone thinking I just ripped it, although can't prove it. For some reason, I still hang around the old glslsandbox)
// I have been doing few other lame tests, but since I liked this particular one, I decided to transfer it here.

float plasma(vec2 p, float iso, float fade)
{
	float c = 0.0;
	for (float i=1.0; i<10.0; ++i) {
		float f1 = i / 0.6;
		float f2 = i / 0.3;
		float f3 = i / 0.7;
		float f4 = i / 0.5;
		float s1 = i / 2.0;
		float s2 = i / 4.0;
		float s3 = i / 3.0;
		c += sin(p.x * f1 + iTime) * s1 + sin(p.y * f2 + 0.5 * iTime) * s2 + sin(p.x * f3 + p.y * f4 - 1.5 * iTime) * s3;
	}

	c = mod(c, 16.0) * 0.5 - 7.0;
	if (c < iso) {
		return 0.0;
	}
	else {
		if (c > 0.5) c = 1.0 - c;
		c *= 2.0;
		return c * fade;
	}
}

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
	vec2 uv = (fragCoord - iResolution.xy * 0.5) / max(iResolution.x, iResolution.y);
	uv *= 2;

	float c = 0.0;
	for (float i=0.0; i<64.0; ++i) {
		float zoom = 1.0 + i * 0.05 + sin(iTime * 0.3) * 0.5;
		vec2 trans = vec2(sin(iTime * 0.3) * 0.5, sin(iTime * 0.4) * 0.3);
		c = plasma(uv * zoom + trans, 0.0, 2.0 / (1.0 + i));
		if (c> 0.001) break;
	}
	fragColor = vec4(c * uv.x, c * uv.y, c * abs(uv.x + uv.y), 0.5) * 2.0;
}

// https://www.shadertoy.com/view/Md3czn