#define PI 3.1415926535897932384626433832795

vec4 hsv_to_rgb(float h, float s, float v, float a)
{
	float c = v * s;
	h = mod((h * 6.0), 6.0);
	float x = c * (1.0 - abs(mod(h, 2.0) - 1.0));
	vec4 color;
 
	if (0.0 <= h && h < 1.0) {
		color = vec4(c, x, 0.0, a);
	} else if (1.0 <= h && h < 2.0) {
		color = vec4(x, c, 0.0, a);
	} else if (2.0 <= h && h < 3.0) {
		color = vec4(0.0, c, x, a);
	} else if (3.0 <= h && h < 4.0) {
		color = vec4(0.0, x, c, a);
	} else if (4.0 <= h && h < 5.0) {
		color = vec4(x, 0.0, c, a);
	} else if (5.0 <= h && h < 6.0) {
		color = vec4(c, 0.0, x, a);
	} else {
		color = vec4(0.0, 0.0, 0.0, a);
	}
 
	color.rgb += v - c;
 
	return color;
}

void mainImage( out vec4 fragColor, in vec2 fragCoord )
{
	float x = fragCoord.x - (iResolution.x / 2.0);
	float y = fragCoord.y - (iResolution.y );
	
	float r = length(vec2(x,y));
	float angle = atan(x,y) - sin(iTime)*r / 200.0 + 1.0*iTime;
	float intensity = 0.5 + 0.25*sin(15.0*angle);
	//float intensity = mod(angle, (PI / 8.0));
	//float intensity = 0.5 + 0.25*sin(angle*16.0-5.0*iTime);
	
	fragColor = hsv_to_rgb(angle/PI, intensity, 1.0, 0.5);
}