#define pi acos(-1.)
#define tau pi*2.

precision highp float;
uniform vec2 resolution;
uniform float time;
uniform sampler2D backbuffer;
out vec4 outColor;

uint seed;
uint hashi( uint x) {
    x ^= x >> 16;
    x *= 0x7feb352dU;
    x ^= x >> 15;
    x *= 0x846ca68bU;
    x ^= x >> 16;
    return x;
}
uint wang(uint a) {
    a = (a ^ 61U) ^ (a >> 16U);
    a = a * 9U;
    a = a ^ (a >> 4);
    a = a * 0x27d4eb2dU;
    a = a ^ (a >> 15);
    return a;
}

#define hash_u_s(s)  ( ( hashi(uint(s)) ) )
#define hash_i_s(s)  ( int( hashi(uint(s)) ) )
#define hash_f_s(s)  ( float( hashi(uint(s)) ) / float( 0xffffffffU ) )
#define hash_v2_s(s)  vec2(hash_f_s(s),hash_f_s(s+12512))
#define hash_f()  ( float( seed = hashi(seed) ) / float( 0xffffffffU ) )
#define hash_v2()  vec2(hash_f(),hash_f())
#define hash_v3()  vec3(hash_f(),hash_f(),hash_f())
#define hash_v4()  vec3(hash_f(),hash_f(),hash_f(),hash_f())

#define hash_v3_s(s)  vec3(hash_f_s(s),hash_f_s(s + 1),hash_f_s(s + 2)

mat2 rot(float n){
  return mat2(cos(n),-sin(n),sin(n),cos(n));
}
float truchet(vec2 p){
    float width = .2;
    
    vec2 q = vec2(p.x,abs(p.y));
    q.y-=2./sqrt(3.);
    float arc = step(width,abs(length(q)-1./sqrt(3.)));
    float line = step(width, abs(p.y));
    return arc*line;
}
vec4 hexagon(vec2 p, float sca)
{
    p = p*sca;
    p.y /= sqrt(3.)/2.;
    float odd_rows = mod(floor(p.y),2.);
    p.x += odd_rows*.5;
    vec2 i_uv = floor(p),
         f_uv = fract(p)*2.-1.;
    
    vec2 q = (vec2(1)-abs(f_uv))*vec2(1.,sqrt(3.));
    
    if(q.x+q.y<.5){
        i_uv = i_uv+vec2(sign(f_uv.x)*.5-odd_rows+.5,sign(f_uv.y));
        f_uv = f_uv-2.*vec2(.5,1.)*sign(f_uv);
    }
    
    return vec4(i_uv, f_uv*vec2(1.,sqrt(3.)/2.));
}
vec3 samp(vec2 p){
  p=vec2(atan(p.y,p.x)/tau-length(p)*2.,length(p));
  float ay = p.y + pow(p.y,1.2);
  float by = log(p.y);
  p.y = mix(ay,by,sin(time)*.5+.5);
  p.y += time*.2 + 45.;
  
  vec2 i_hex = hexagon(p, 2.0).xy,
       f_hex = hexagon(p, 2.0).wz;
  i_hex.x = mod(i_hex.x,8.);
  
  float val = truchet(f_hex*rot(floor(hash_f_s(uint(i_hex.y*68387.+i_hex.x))*8.)*tau/6.));
  
  vec3 col = mix(vec3(0,.03,.01),vec3(.2,.1,.0),step(.5,val));
  
  return col;
}

void main(){
  vec2 r=resolution,
       p=gl_FragCoord.xy/r;p-=.5;p.x*=r.x/r.y;
  
  float ep = .85/r.y;
  int os = 2;
  vec3 col;
  for(int i=-os; i<=os; i++){
    for(int j=-os; j<=os; j++){
      vec2 off = vec2(i,j)*ep/float(os);
      col += samp(p+off);
    }
  }
  col/=float(os)*float(os);
  
  outColor = vec4(pow(max(col,0.),vec3(.454545)),1.);
}