Alt+Enter for windowed mode.
Thanks for trying to help.
As you suggested, the game is in a tiny window. It is even possible to manually resize the resolution, but it is almost impossible to get exactly 1920x1080 by dragging the mouse. And without getting it right, the pixels become irregular.
For Alt + Enter to work, at the very least, the resolution would have to be configurable within the game. Since it isn't, your solution isn't viable.
At least one or two solutions are needed:
1a. configure the resolution and enable windowed mode.
2a. configure the resolution and in full screen mode fill the excess with black bars.