I wrote a small 2D game once, where the Earth is attacked by a swarm of satellites in polar orbits. Your ship is launched from the surface, but after that it's

I wrote a small 2D game once, where the Earth is attacked by a swarm of satellites in polar orbits. Your ship is launched from the surface, but after that it's up to you to put yourself in orbit, using thrusters. Thinks Asteroids with gravity. It really taught me a lot about how an orbit's shape changes when thrust is applied in different directions, at different points in an orbit. For example, a good way to circularise an orbit from an elliptical, a small tangential thrust at apogee during each orbit would eventually place the spacecraft in a circular orbit with a radius roughly equal to the apogee distance of the elliptical orbit... or to say it another way, perigee would increase until it equalled apogee... Anyway, the point being that I never would have understood any of this no matter how many times I read 2010, until I wrote that little game. Some things need to be experienced to really grok.