precision mediump float;
varying vec2 v_texCoord;
uniform sampler2D u_texture;
uniform vec2 u_resolution;
uniform float u_intensity; // 0-1
uniform float u_block;     // 4-64
uniform int   u_seed;      // 1-999

float hash(vec2 p) {
  return fract(sin(dot(p, vec2(127.1, 311.7))) * 43758.5453 + float(u_seed) * 123.456);
}

void main() {
  vec2 uv = v_texCoord;