precision mediump float;
varying vec2 v_texCoord;
uniform sampler2D u_texture;
uniform vec2 u_resolution;
uniform float u_track;     // tracking noise (0-1)
uniform float u_noise;     // noise level (0-0.5)
uniform float u_bleed;     // color bleed (0-1)

float hash(vec2 p) {
  return fract(sin(dot(p, vec2(127.1, 311.7))) * 43758.5453);
}

void main() {
  vec2 uv = v_texCoord;