A Physics Video Game: Kirchhoff's Revenge

I remember the day I came to truly understand the concept of orbit--and why astronauts in the space station seem to be in zero-g, even though they're only 250 miles from Earth's surface, experiencinga gravitational pull close to 90% of what we feel here on Earth. It wasn't during a physics class, or during my time here at PhysicsCentral. I was in my friend's basement, probably 12 years old...playing Super Mario Galaxy.If you're unfamiliar with the game: it's a 3D take on the classic Nintendo pla...