cosine palette

  vec3 palette(float t) {
    vec3 a = vec3(0.5, 0.5, 0.5);
    vec3 b = vec3(0.5, 0.5, 0.5);
    vec3 c = vec3(1.0, 1.0, 0.5);
    vec3 d = vec3(0.80, 0.90, 0.30);

    return a + b * cos(6.28318 * (c * t + d));
  }
  
  vec3 col = palette(uv.y + 0.5);