​

varying vec2 pos;

​

uniform float millis; 

​

const vec4 brickColour = vec4(0.8, 0.3, 0.2, 1.);

​

float inSeg(float p) {

  return step(0.05, p) * (1. - step(0.95, p));

}

​

float inRect(vec2 p) {

  return inSeg(p.x) * inSeg(p.y);

}

​

void main() {

  vec2 p = pos * vec2(9., 16.);

  vec2 f = fract(p);

  vec2 i = floor(p);

  p = fract(f - vec2(mod(i.y, 2.) * 0.5, 0.));

  float brick = inRect(p);

  gl_FragColor = vec4(1.) * (1. - brick) + brickColour * brick * (0.75 + p.y * 0.5);

}

​