i use the vec_to_screen and the oppossite of it quite a bit and, depending on what you want, im not sure it would help you. if your going for a Black & White feel, i probably wouldnt use the two functions. what i would do is just ignore the mouse position entirely and use the mouse speed to change the position of the model. so that if you move the mouse up quickly, the model would move foward quickly. this way, you could also implement gravity for the 'hand' and have it drag along the ground without it affecting where it is relative to the mouse coordinates.