#extension GL_OES_standard_derivatives : enable
 
precision highp float;
 
uniform float time;
uniform vec2 mouse;
uniform vec2 resolution;
 
float random (in vec2 _st) {
    return fract(sin(dot(_st.xy,
                         vec2(12.9898,78.233)))*
        43758.5453123);
}
 
// Based on Morgan McGuire @morgan3d
// https://www.shadertoy.com/view/4dS3Wd
float noise (in vec2 _st) {
    vec2 i = floor(_st);
    vec2 f = fract(_st);
 
    // Four corners in 2D of a tile
    float a = random(i);
    float b = random(i + vec2(1.0, 0.0));
    float c = random(i + vec2(0.0, 1.0));
    float d = random(i + vec2(1.0, 1.0));
 
    vec2 u = f * f * (3.0 - 2.0 * f);
 
    return mix(a, b, u.x) +
            (c - a)* u.y * (1.0 - u.x) +
            (d - b) * u.x * u.y;
}
 
#define NUM_OCTAVES 5
 
float fbm ( in vec2 _st) {
    float v = 0.;
    float a = .5;
    vec2 shift = vec2(100.);
    // Rotate to reduce axial bias
    mat2 rot = mat2(cos(.5), sin(.5),
                    -sin(.5), cos(.5));
    for (int i = 0; i < NUM_OCTAVES; ++i) {
        v += a * noise(_st);
        _st = rot * _st * 2. + shift;
        a *= .5;
    }
    return v;
}
 
vec2 random2( vec2 p ) {
    return fract(sin(vec2(dot(p,vec2(123.,456.)),dot(p,vec2(789.,158.))))*12345.);
}
 
void main() {
    vec2 st = gl_FragCoord.xy/resolution.xy;
	
    vec3 color = vec3(0.0);
    vec2 rand = random2(vec2(0.));
    float zoom = sin(rand.x+time*.2);
    st -= vec2(zoom);
    st *= sin(time/8.)*10.;
    
   
    mat2 rot = mat2(cos(time*.2+rand.x), sin(rand.y+time*.3),
                    -sin(rand.y+time*.5), cos(rand.x+time*.4));
    
    st *= rot;
    
    vec2 gv = floor(st);
    vec2 id = fract(st);
    
    float m_dist = 1.;  // minimum distance
 
    for (int y= -1; y <= 1; y++) {
        for (int x= -1; x <= 1; x++) {
            // Neighbor place in the grid
            vec2 neighbor = vec2(float(x),float(y));
 
            // Random position from current + neighbor place in the grid
            vec2 point = random2(gv + neighbor);
	
	    // Animate the point
            point = .5 + .5*sin(time + 6.3*point);
 
	    // Vector between the pixel and the point
            vec2 diff = neighbor + point - id;
 
            // Distance to the point
            float dist = length(diff);
 
            // Keep the closer distance
            m_dist = min(m_dist, dist);
        }
    }
    
    color += m_dist;
 
    // Draw cell center
    color += 1.-step(-.4, m_dist);
 
    vec2 q = vec2(0.);
    q.x = fbm(gv);
    q.y = fbm( gv + vec2(1.));
 
    vec2 r = vec2(0.);
    r.x = fbm( gv + q + vec2(1.7,9.2)+ 0.15*m_dist );
    r.y = fbm( gv + q + vec2(8.3,2.8)+ 0.15*m_dist);
 
    float f = fbm(gv+r);
 
    color += mix(vec3(.8,.9,.5),
                vec3(.6,0.7,.5),
                clamp((f*f)*4.,.0,1.));
 
    color = mix(color,
                vec3(.9,.3,0.3),
                clamp(length(q),0.,1.));
 
    color = mix(color,
                vec3(0.8,1.0,.5),
                clamp(length(r.x),0.0,1.0));
 
    gl_FragColor = vec4((f*f*f+1.2*f*f+.6*f)*color,1.);
}