#version 330 core
out vec4 FragColor;

in vec3 WorldPos;

void main() {
  /* Define colours for the top and bottom of the sky. */
  vec3 zenithColor = vec3(0.3, 0.5, 0.8);
  vec3 horizonColor = vec3(0.7, 0.85, 1.0);

  float blendFactor = (normalize(WorldPos).y + 1.0) / 2.0;

  /* Blend the two colours. */
  vec3 finalColor = mix(horizonColor, zenithColor, blendFactor);

  FragColor = vec4(finalColor, 1.0);
}