I created python script that solve equations using runge kutta method. Everything is working as it should be, I created IPO curves as well so I can get keyframes and render things (thanks to your help), but now I am trying to somehow make things interactive - I am trying use Blender Game Engine so I can change input values interactively. I checked some BGE tutorials but werent very helpful because there were no mention about working with existing script. I tried to use Sensors and controllers things (so that if i press UP arrow it will run script), but nothing happened in BGE (i guess i will have to change scene into BGE scene or something like that). I hope I explained my situation clearly and I will be grateful for any help.