So I have set the screen mode to be 900 width and 600 height. Now when I define a texture of an image of 50px per 50px and I set it to be the texture of a sprite which has 50 width and 50 height I see that the rectangle is stretched: the height is less than the width. While if I set the screen to be 600x600, then it is ok. Why is that? How can I change this?