The demo visually illustrates the concept of vector flux, showing that the flow crossing a surface is determined exclusively by the component of the current density vector ( $J$ ) that is perpendicular to the surface ( $J_{\perp}$ ), which is mathematically captured by the scalar product $J$ . $n$. As the $J$ vector rotates $360^{\circ}$ around the origin, the animation dynamically updates its decomposition, making it clear that when $J$ points predominantly outward (acute angle with the normal $n$ ), the flux is positive (outflux), and when $J$ points inward (obtuse angle with $n$ ), the flux is negative (influx). The flux drops to zero precisely when $J$ is tangential to the surface, as the perpendicular component $J_{\perp}$ vanishes entirely at that orientation.