precision mediump float;

#endif

​

uniform vec2 u_resolution;

uniform float u_time;

​

mat2 scale(vec2 scale) {

  return mat2(scale.x, 0.0, 0.0, scale.y);

}

​

float circleShape(vec2 position, float radius) {

  return step(radius, length(position - vec2(0.5)));

}

​

void main() {

  vec2 coord = gl_FragCoord.xy/u_resolution;

  vec3 color = vec3(0.0);

  coord -= vec2(0.5);

  coord = scale(vec2(sin(u_time) + 2.0)) * coord;

  coord += vec2(0.5);

  color += vec3(circleShape(coord, 0.2));

  gl_FragColor = vec4(color, 1.0);

}