#ifdef GL_ES
precision highp float;
precision mediump int;
#endif

uniform sampler2D u_texture;

uniform vec2 u_center;
uniform vec2 camerapos;
uniform vec2 screensize;
uniform float time;

varying vec4 v_color;
varying vec2 v_texCoord;

const float tau = 6.28318530717958647692;
const float tscl = 0.4;

// Gamma correction
#define GAMMA (2.2)

vec3 ToLinear(vec3 col ){
	// simulate a monitor, converting colour values into light values
	return pow( col, vec3(GAMMA) );
}

vec3 ToGamma(vec3 col ){
	// convert back into colour values, so the correct light will come out of the monitor
	return pow( col, vec3(1.0/GAMMA) );
}

float srand(vec2 co){
    return fract(sin(dot(co.xy ,vec2(12.9898,78.233))) * 43758.5453);
}

vec4 Noise(ivec2 x ){
	return vec4(srand((vec2(x)+0.5)/256.0));
}

void main(){
    vec4 resultc = texture2D(u_texture, v_texCoord.xy);
    
    if(resultc.a > 0.0){
    
        vec2 coords = v_texCoord.xy*screensize;

        vec3 ray;
        ray.xy = 2.0*(coords-screensize.xy*.5)/screensize.x;
        ray.z = 1.0;

        float literallyzero = 0.000000000001;

        float offset = time/60.0*.5 * tscl + camerapos.x * u_center.x * resultc.r * literallyzero;	
        float speed2 = 0.3;
        float speed = speed2+.1;
        offset += .1;
        offset *= 2.0;

        vec3 col = vec3(0.0);

        vec3 stp = ray/max(abs(ray.x),abs(ray.y));

        vec3 pos = 2.0*stp+.5;
        for ( int i=0; i < 20; i++){
	        float z = Noise(ivec2(pos.xy)).x;
	        z = fract(z-offset);
	        float d = 50.0*z-pos.z;
	        float w = pow(max(0.0,1.0-8.0*length(fract(pos.xy)-.5)),2.0);
	        vec3 c = max(vec3(0),vec3(1.0-abs(d+speed2*.5)/speed,1.0-abs(d)/speed,1.0-abs(d-speed2*.5)/speed));
	        col += 1.5*(1.0-z)*c*w;
	        pos += stp;
        }
        
        vec3 color = ToGamma(col);
        
        if(color.r > 0.3 && color.b > 0.3){
            color = vec3(240.0, 245.0, 255.0) / 255.0;
        }else{
            color = vec3(0.0);
        }
        
        gl_FragColor = vec4(color,1.0);
    }else{
        gl_FragColor = vec4(0.0);
    }
	
	
}