varying vec3 vertex_light_position;
varying vec3 vertex_normal;

void main() {
	// Set the diffuse value (darkness). This is done with a dot product between the normal and the light
	// and the maths behind it is explained in the maths section of the site.
	float diffuse_value = max(dot(vertex_normal, vertex_light_position), 0.0);

	// Set the output color of our current pixel
	gl_FragColor = gl_Color * diffuse_value;
}