accessing testApp variables from other classes

how do i create global variables within testApp that can be accessed by any and all objects instantiated within it?

i’m just starting out with OF and c++ and am having some trouble accessing variables located in the testApp from an object instantiated within testApp.

i can’t figure out how to refer to the testApp object. in main.cpp, i’ve replaced <ofRunApp (new testApp());> with the code below to attempt to instantiate the testApp object with the name APP so i can refer to it later.

// this kicks off the running of my app
// pass in width and height too:
// ofRunApp( new testApp());
testApp APP;

but if i try to access a function of testApp from within another object of a different class by referring to it as APP.[something], i get an error that APP has not been declared.

seems like i’m missing something really simple, but i can’t figure it out.
i know i can write a function to pass variables into the other object from testApp, but that seems highly redundant.