Another beginner's question: How device orientation toggles fullscreen?

Hi there
As a complete rookie in krpano code scripting and setup I need some help, please!
OK, my question is:
How a mobile device orientation (horizontal or portrait) toggles fullscreen on and off in a krpano tour? I mean, which part of the script triggers this behaviour on mobile devices?
I am asking about this script information because I have to find a way to alter the script and achieve the same thing in a tour built in Panotour where I haven't been capable to get it working. I can only hope it'd be possible to happen this way.
I know there is still a long way for me to go before I get to the light at the other end of the tunnel and start building tours in the endless krpano coding heavens *smile*.
Thanks in advance!

Thanks a lot for your very helpful response, Klaus!
And thanks for all the support you provide everyone here!