Could you add a recommendation to run the game in maximized mode (or fullscreen if that's available)?
The mouse cursor is not confined and is visible and active during game play, not the usual setup. Because of this, clicks can accidentally go to other apps when you move the mouse during gameplay and lead the cursor over another window.
In other words, since the mouse is currently "loose", it's easy, during heavy gameplay, for the mouse cursor to eventually drift off the game window and then activate or clickin unwanted apps and make problems. It's pretty scary in my X11 setup where clicks and drags go to background apps without changing focus. (I actually like this behavior in text apps, since it aids the X11 mouse button-based copy/paste workflow...)
Fortunately the workaround is easy. Maximizing the window avoids a lot of the dangers for the most part. I assume most people already did this.