Added:
an Aspect Ratio option under Settings > Video
window resize (see below)
Due to the UI being designed around a 16:9 ratio, the menus and UI may have some visual oddities, but should all be centered. Also, if playing in windowed mode, the window can be resized by pressing the "windows" key (WinKey/Start Key) and dragging the corners. It may be a little awkward, but otherwise the mouse can easily move outside the window and cause issues that way.