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varying vec2 pos;

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uniform float millis;

​

void main() {

  vec2 q = pos - vec2(0.5, 0.5);

  float d = length(q);

  vec3 outerEyeColour = vec3(0.2, 0.6, 1.0);

  vec3 innerEyeColour = vec3(1., 1., 0.);

  vec3 pupilColour = vec3(0.);

  float innerRad = 0.1;

  float outerRad = 0.4;

  float inner = 1. - step(innerRad, d);

  float outer = (1. - step(outerRad, d)) * (1. - inner);

  float eyeLerp = sqrt(sqrt((d - innerRad) / (outerRad - innerRad)));

  vec3 eyeColour = mix(innerEyeColour, outerEyeColour, eyeLerp);

  float a = atan(q.y, q.x);

  eyeColour.r += sin(d * 50.) * cos(a * 100.) * 0.2;

  eyeColour.g += cos(d * 50.) * sin(a * 100.) * 0.2;

  vec3 col = eyeColour * outer + pupilColour * inner;

  gl_FragColor = vec4(col, 1.);

}