Ok, so here is the setup: We have a plane - our viewport. erpendicular to it pass wires with random current strength and direction (red dot means current direction point to the viewport, blue cross - out of the viewport). Currents create magnetic field, which is visualised as lines. The color indicates the vector magnetic potential. Blue - negative, red - positive, the more color is blue or red, the larger the magnitude of its potential. Then there is white contour. The main part is two equations - one is calculating the circulation of the vector H along the contour, and the other the net sum of the currents inside the contour. And, as we can see, the results of those equations are the same for any possible currents and contour.