ELI7VH

  
  uniform float time;
  varying vec2 vUv;
  
  void main() {
    vec3 color = vec3(1.0);
    float sun = step(mod(vUv.y * 20. + time, 1.), -0.2 + 0.35 * vUv.y * 3.7);
    color.x *= sun;
    color.y *= sun * (0.6 + vUv.y - 0.7 );
    color.z = 0.;