LBreakout2 Problem

I hadn't used LBreakout2 in ages. The last time I used it, I think it might have even been another version.

Nevertheless, now that I decided to use it, it's coming up in s small window instead of in FULL screen. And the button at the upper right of the window that would allow me to maximize the window is not active.

Any idea what's going on? How do I maximize the window? Or what am I doing wrong? I so easily played it before on FULL screen without a problem.

Or is it a problem with this version?
My version is 2.6.3.