#version 300 es

precision highp float;

​

uniform vec2 resolution;

uniform float time;

out vec4 fragColor;

​

const float TAN30 = 1.0 / sqrt(3.0);

​

vec3 hue(vec3 col, float a) {

  const vec3 k = vec3(TAN30);

  float c = cos(a);

  return col * c + cross(k, col) * sin(a) + k * dot(k, col) * (1.0 - c);

}

​

void main(void) {

  vec2 uv = gl_FragCoord.xy / resolution.xy;

  float s = clamp(0.35 + 0.35 * sin(3.0 * time + uv.y * resolution.y * 3.0), 0.0, 1.0);

  float scanLines = pow(s, 1.33);

  float v = (0.0 + 1.0 * 21.0 * uv.x * uv.y * (1.0 - uv.x) * (1.0 - uv.y));

  vec3 vignette = vec3((pow(abs(v), 0.5)));

  vec3 color = hue(uv.yxx, time * 0.5) * scanLines * vignette;

  fragColor = vec4(color, 1.0);

}