Triangles rotation pattern

float triDist(vec2 p){
  float f = smoothstep(0.0,0.01,p.x-p.y);
  f*=  smoothstep(0.0,0.01,-p.x-p.y);
  f*=  smoothstep(0.0,0.01,0.5+p.y);
  return f;
}

void main(){
  vec2 p = gl_FragCoord.xy/iResolution;
  p-=0.5;
  p.x *= iResolution.x/iResolution.y;
  p*=20.0;

  float gridsize = 1.5;

  vec2 pcenter = floor((p)/gridsize);

  float angle = 1.0+iGlobalTime+sin(1.0*pcenter.x);
  angle = angle;

  vec2 prot=mod(p,gridsize)-gridsize/2.0;
  prot  = mat2(
    cos(angle),
    sin(angle),
    -sin(angle),
    cos(angle)
  )*prot;

  vec2 ptrans = prot-vec2(0.0,0.0);
  float f = triDist(ptrans);

  ptrans = mat2(
    cos(3.14159/1.0),
    sin(3.14159/1.0),
    -sin(3.14159/1.0),
    cos(3.14159/1.0)
  )*prot;
  ptrans = ptrans-vec2(0.0,-0.0);

  f = max(f,triDist(ptrans));

  float m = 0.5+0.5*sin(123.0*pcenter.x+5587.0*pcenter.y+3.0*iGlobalTime);
  gl_FragColor = vec4(m*f,0.0,0.0,1.0);
}