I'm not going to bury the lede. The blog post below describes my experience programming; a later post will explain how I'm going to use the program next year. The program shows the flux as brighter or dimmer shades of red (flux out of the surface) and blue (flux into the surface). Play with it. Zoom in and out. Rotate the sphere. Edit and break the program. (I tried to write a lot in the comments, so hopefully you can change a number or two and see what happens.) Give me suggestions. (My students like running it in fullscreen. Find that in the menu at the upper left of the screen.) Here you go: