// for the current mouse position on the screen, where does that correspond to in the world?
glm::vec2 World::world_position_for_mouse(const glm::vec2 mouse_position,
                                          const glm::mat4 projection_matrix,
                                          const glm::mat4 view_matrix)
{
    int window_width;
    int window_height;
    this->graphics.get_window_dimensions(window_width, window_height);

    const int mouse_x = mouse_position[0];
    const int mouse_y = mouse_position[1];

    GLfloat normalized_mouse_x =  (2.0f * mouse_x) / window_width - 1.0f;
    float normalized_mouse_y = 1.0f - (2.0f * mouse_y) / window_height;


    glm::vec3 normalized_mouse_vector = glm::vec3(normalized_mouse_x, normalized_mouse_y, 1.0f);

    glm::vec4 ray_clip = glm::vec4(normalized_mouse_vector.xy(), -1.0, 1.0);

    glm::vec4 ray_eye = glm::inverse(projection_matrix) * ray_clip;
    ray_eye = glm::vec4(ray_eye.xy(), -1.0, 0.0);

    glm::vec3 ray_world = (glm::inverse(view_matrix) * ray_eye).xyz();

    ray_world = glm::normalize(ray_world);

    float l = -(camera.z / ray_world.z);


    return {camera.x + l * ray_world.x, camera.y + l * ray_world.y};
}