Question Few question and tips about Battery health and usage AN515-54.

Hello guys. i have a few question about my Laptop battery and i need some tips about how it's better to get used. i'd be so glad if you guys help me on this.

Is it OK to play some medium and low-demand games with my Battery? (Like 2010-2012 games) or i ALWAYS need to play with AC?
Is it OK to plug in and play game?

here's an example scenario :
a)Battery is at 50%. i plug in, play game, battery goes to 100%.
b)i quit the game, do normal and routine jobs on battery (like watching movies and etc.),
c) i plug in and do games again. battery goes to 100% and stays there for at least 40-60 mins.

So, battery half of times goes above 80% and stays there. (I've read too many articles about you SHOULD maintain your battery between 20-80% always). and therefore there could be a health degradation, right?

Thanks in advance.
P.S: i have AN515-54.