precision mediump float;

#endif

#define PI 3.14159265359

​

uniform vec2 u_resolution;

uniform float u_time;

uniform sampler2D u_texture;

uniform vec3 u_background;

​

vec2 rotate(vec2 _st, float _angle) {

  float s = sin(_angle);

  float c = cos(_angle);

  return (_st - 0.5) * mat2(c, -s, s, c) + 0.5;

}

​

vec2 scale(vec2 _st, float _scale, float _half) {

  return (_st - _half) * _scale + _half;

}

​

vec4 blend(vec4 _color1, vec4 _color2) {

  return _color1 * _color1.a + _color2 * (1. - _color1.a);

}

​

vec4 clamp_tex(vec2 _pos, vec4 _tex) {

  _tex.a *= step(_pos.x, 1.0)

         * step(_pos.y, 1.0)

         * step(0., _pos.x)

         * step(0., _pos.y);

  return _tex;

}

​

void main() {

  vec2 st = gl_FragCoord.xy / u_resolution;

  float ratio = u_resolution.x / u_resolution.y;

  st.x *= ratio;

  vec2 grid = st * 3.;

  vec2 floor = floor(grid);

  float a = mod(floor.x, 2.) * 2. - 1.;

  float b = mod(floor.y, 2.) * 2. - 1.;

  // grid.x += u_time * 0.2;

  vec2 grid_1 = grid;

  vec2 grid_2 = grid;

  grid_1.y += 0.5 * u_time;

  grid_1.x += 0.1 * u_time;

  grid_2.y += 0.5 * -u_time;

  grid_2.x += 0.5 * -u_time;

  grid_1 = scale(grid_1, 1.4, 0.5);

  grid_2 = scale(grid_2, 1.4, 0.5);

  vec2 f1 = fract(grid_1);

  vec2 f2 = fract(grid_2);

  f1 = scale(f1, 1.3, 0.5);

  f1 = rotate(f1, u_time * 0.8);

  f2 = scale(f2, 1.3, 0.5);

  f2 = rotate(f2, -u_time);

  vec4 tex1 = texture2D(u_texture, f1);

  vec4 tex2 = texture2D(u_texture, f2);

  tex1 = clamp_tex(f1, tex1);

  tex2 = clamp_tex(f2, tex2);

  vec4 final_tex = blend(tex1, tex2);

  // vec4 color = blend(final_tex, vec4(u_background, 1.));

  vec4 color = final_tex;

  // vec4 color = vec4(uv.x, uv.y, 1.0, 1.0);

  if (color.a <= 0.)

    discard;

  gl_FragColor = color;

}