// Author:
// Title:

#define PI 3.14159265359
#define PI_2  6.28318530718

#ifdef GL_ES
precision mediump float;
#endif

uniform vec2 u_resolution;
uniform vec2 u_mouse;
uniform float u_time;

float line(float pos, float dist) {
    const float width = 0.010;
    return smoothstep(dist-width, dist, pos) * (1.0 - smoothstep(dist, dist + width, pos));
}

float pulse(vec2 st, vec2 p, float scanline) {
    return smoothstep(0.068, 0.0, distance(st, p)) * (pow(scanline, 1.592)) * 2.136;
}

//  Function from Iñigo Quiles
//  https://www.shadertoy.com/view/MsS3Wc
vec3 hsb2rgb( in vec3 c ){
    vec3 rgb = clamp(abs(mod(c.x*6.0+vec3(0.0,4.0,2.0),
                             6.0)-3.0)-1.0,
                     0.0,
                     1.0 );
    rgb = rgb*rgb*(3.0-2.0*rgb);
    return c.z * mix( vec3(1.0), rgb, c.y);
}

void main() {
    vec2 st = gl_FragCoord.xy/u_resolution.xy;
    
    st -= vec2(0.5);
    st *= 2.0;
    float t = fract(u_time / 2.0);
    
	float d = distance(st, vec2(0.0));
    float scanline = fract((atan(st.x, st.y)) / PI_2 - t);
    float c = pow(scanline, 2.0);
    c *= (1.0 - step(1.0, d));
    float radial = c / 0.8;
    radial += line(d, 0.2);
    radial += line(d, 0.4);
    radial += line(d, 0.6);
    radial += line(d, 0.8);
	radial += line(d, 1.0);
    radial += line(st.x, 0.000);
    radial += line(st.y, 0.0);
    
	radial += pulse(st, vec2(0.360,-0.200), scanline);
	radial += pulse(st, vec2(-0.140,0.230), scanline);
	radial += pulse(st, vec2(0.460,0.200), scanline);
	radial += pulse(st, vec2(0.240,0.450), scanline);
	radial += pulse(st, vec2(0.610,0.390), scanline);
	radial += pulse(st, vec2(0.430,0.700), scanline);
    
    vec3 base = vec3(0.0);
    vec3 color = base + vec3(0.040,0.470,0.010) * radial;
    
    // crop to circle
    color *= (1.0 - step(1.0, d));
    gl_FragColor = vec4(color,1.0);
}