Nuts

Code

precision mediump float;
uniform float u_time;
varying vec2 v_texcoord;
#define PI 3.14159265358979323846

float rows = 10.0;

vec2 brickTile(vec2 _st, float _zoom){
  _st *= _zoom;
  if (fract(_st.y * 0.5) > 0.5){
      _st.x += 0.5;
  }
  return fract(_st);
}

vec2 rotate2D(vec2 _st, float _angle){
  _st -= 0.5;
  _st =  mat2(cos(_angle),-sin(_angle),
              sin(_angle),cos(_angle)) * _st;
  _st += 0.5;
  return _st;
}

void main(){

  vec2 st = v_texcoord;
  st = brickTile(st,rows);

  float angle = PI*0.25*cos(u_time*0.5);

  if (fract(v_texcoord.y * 0.5 * rows) > 0.5){
    angle *= -1.0;
  }

  st = rotate2D(st,angle);

  st *= 2.0;
  float pct = (1.0+cos(PI*st.x))*0.5;

  vec3 color = vec3( 1.0-smoothstep( 0.5,0.6, pow(pct,st.y) ) * 1.0-smoothstep( 0.79,0.81, pow(pct,2.0-st.y ) ));

  gl_FragColor = vec4(color,1.0);
}