window and full screen stuck as square

[WitheredSouls]

When I opemn the game the window is a square and when I hit F8 the square stays with thick black borders.
Whenever I played before it was a rectangle and not a square, I am not sure how to fix this ? It bothers me a lot as half of my screen is covered by black borders

[GIR]

The game's native resolution is 640x480, or a 4:3 ratio. So if you're playing on a display with a wider ratio than that (most monitors are 16:9 now), you'll see the black borders.