precision mediump float;

#endif

​

uniform vec2 u_resolution;

uniform float u_time;

uniform vec2 u_mouse;

uniform sampler2D u_img;

​

float size = 6.0;

float speed = -10.0;

bool flip = true;

​

void main() {

  vec2 coord = gl_FragCoord.xy / u_resolution;

  vec3 color = vec3(0.0);

  vec4 image = texture2D(u_img, coord);

  if(flip){

    image.a = sin(floor(coord.x * size) - u_time * speed);

  } else {

    image.a = sin(floor(coord.y * size) - u_time * speed);

  }

  gl_FragColor = image;

}