A simple program which expands a set of double brackets you enter. Press on one of the coloured boxes to change the corresponding value, the equations will then update automatically (even when the project is stopped, thanks to some magic). Negative numbers are supported, but look bad on the display (+ -3), and decimal numbers should work. Entering things other than numbers may completely break everything, I've not tested that and done nothing to prevent it for simplicity's sake to be careful with that. Everything was made by me.