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);
}