#extension GL_OES_standard_derivatives : enable

varying float vTime;
#define M_PI 3.1415926535897932384626433832795
varying vec2 vTexCoord;

//#define vTime (vTime * vTime * 0.05)

vec2 rand2(vec2 p)
{
    p = vec2(dot(p, vec2(102.9898,78.233)), dot(p, vec2(26.65125, 83.054543)));
    return fract(sin(p) * 43758.5453);
}

float rand(vec2 p)
{
    return fract(sin(dot(p.xy ,vec2(505.90898,18.233))) * 43037.5453);
}

// Thanks to David Hoskins https://www.shadertoy.com/view/4djGRh
float stars(in vec2 x, float numCells, float size, float br)
{
    vec2 n = x * numCells;
    vec2 f = floor(n);

	float d = 1.0e10;
    for (int i = -1; i <= 1; ++i)
    {
        for (int j = -1; j <= 1; ++j)
        {
            vec2 g = f + vec2(float(i), float(j));
			g = n - g - rand2(mod(g, numCells)) + rand(g);
            // Control size
            g *= 1. / (numCells * size);
			d = min(d, dot(g, g));
        }
    }

    return br * (smoothstep(.95, 1., (1. - sqrt(d))));
}


void main()
{
    vec2 coord = vTexCoord;

	vec2 tmp = coord;

	coord.x = tmp.y;
	coord.y = tmp.x;

    vec3 result = vec3(0.);
    result += stars(vec2(coord.x + vTime * 2.00,coord.y) , 1., 0.10, 2.)  * vec3(.74, .74, .74);
    result += stars(vec2(coord.x + vTime * 1.10,coord.y) , 1., 0.10, 2.)  * vec3(.74, .74, .74);
    result += stars(vec2(coord.x + vTime * 0.8,coord.y) , 1., 0.10, 2.)  * vec3(.74, .74, .74);
    result += stars(vec2(coord.x + vTime * 0.5,coord.y) , 2., 0.09, 2.) * vec3(.74, .74, .74);
    result += stars(vec2(coord.x + vTime * 0.2,coord.y) , 4., 0.08, 2.) * vec3(.74, .74, .74);
    result += stars(vec2(coord.x + vTime * 0.05,coord.y), 8., 0.05, 1.) * vec3(.74, .74, .74);
    result += stars(vec2(coord.x + vTime * 0.025,coord.y), 10., 0.05,0.8) * vec3(.95, .95, .95);
    result += stars(coord  , 20., 0.025, 0.5) * vec3(.9, .9, .95);



	gl_FragColor = vec4(result, 1.0);
//    gl_FragColor = vec4(1.0*(vTexCoord.x/vResolution.x), 0.0, 0.0, 1.0);



    // bar layer open scene ;
    // vec2 bl = gl_FragCoord.xy / vResolution.xy;

    // if(bl.y>.50-min(vTime/20.,0.4) ^^ bl.y<0.50+min(vTime/20.0,.4))  gl_FragColor  = vec4(0.0,sqrt(coord.y+0.1),0.3,1.0);
}