Having trouble with fullscreen

[Angushjalmur]

Hello there, just started playing and I'm having trouble staying in fullscreen mode.

It seems like if I click anywhere on the screen that wouldn't be within the game window in windowed mode, it kicks me out of fullscreen. I can't seem to expand the window to fill the screen either. Is there any way to correct this? I've chosen the resolution closest to my monitor. I'm running Windows 10 if that makes a difference.

Thanks