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  float shape(vec2 p, int N, float size){
    p = p * 2. - 1.;
    
    float a = atan(p.x, p.y) + PI;
    float r = TWO_PI / float(N); 
    float l = length(p);
    
    float d = cos(floor(.5 + a / r) * r - a) * l;
    
    return step(size, d);

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vec2 rotate(vec2 v, float a) {
	float s = sin(a);
	float c = cos(a);
	mat2 m = mat2(c, -s, s, c);
	return m * v;
}

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mat4 rotationMatrix(vec3 axis, float angle) {
    axis = normalize(axis);
    float s = sin(angle);
    float c = cos(angle);
    float oc = 1.0 - c;
    
    return mat4(oc * axis.x * axis.x + c,           oc * axis.x * axis.y - axis.z * s,  oc * axis.z * axis.x + axis.y * s,  0.0,
                oc * axis.x * axis.y + axis.z * s,  oc * axis.y * axis.y + c,           oc * axis.y * axis.z - axis.x * s,  0.0,
                oc * axis.z * axis.x - axis.y * s,  oc * axis.y * axis.z + axis.x * s,  oc * axis.z * axis.z + c,           0.0,
                0.0,                                0.0,                                0.0,                                1.0);

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    vec2 distortion(vec2 p, float freq, float amp, float t, float map, float speed){
          float phase = -1. * speed * freq;
      
          float x = p.y * freq + t * phase;
          float y = p.x * freq + t * .001 * phase;   
      
          float distX = cos(x+y) * amp;
          float distY = sin(x-y) * amp;
      
          vec2 distortion = vec2(distX * map, distY * map);  

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mat2 scale2D(vec2 _scale){
    return mat2(_scale.x,0.0,
                0.0,_scale.y);
}

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float random (vec2 st) {
    return fract(sin(dot(st.xy,
                         vec2(12.9898,78.233)))*
        43758.5453123);
}

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    float voronoi(vec2 uv){
      float t = u_time;

      vec2 i_st = floor(uv * 5.);
      vec2 f_st = fract(uv * 5.);   

      float m_dist = 1.;
      vec2 m_point;
      
      for(int x = -1; x <= 1; x++){

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vec2 centeredAspectRatio(vec2 uv, vec2 factor){
    return ( uv - .5 ) * factor + .5;
}

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vec2 centerUV(vec2 coord, vec2 coord2){
  return (coord - .5 * coord2) / min(coord2.x, coord2.y);
}

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mat3 gx = mat3(-1., 0., 1., -2., 0., 2., -1., 0., 1.);
mat3 gy = mat3(-1., -2., -1., 0., 0., 0., 1., 2., 1.);

float sobelEdge(sampler2D u_text,vec2 resolution, vec2 uv){
  float h = 0.;
  float v = 0.;
  for(int y = 0; y < 3; y++){
    for(int x = 0; x < 3; x++){
      vec2 d = vec2(y, x) / resolution;
      vec4 img = texture2D(u_text, uv + d);