Algodoo

Hi everyone , here i'm trying to calculate the distance between both circles with this method: distance = (redpos(x) - greenpos(x)) - (redpos(y) - greenpos(y)) . To a not really advanced user this seems good , but to other people seems not really good ; when red circle goes up (y) the distance between both circles decreases , and that's strange becouse it have to do the contrary , for that strange reason , i request help please! I hope you understood all what i said! (my english is not good)