Rocvent Mine Ventilation
This was once an interactive piece but since Flash has been banished to the netherworld of forgotten technologies, the best I can do is show a video of how it functions. This was a freelance job, which I did in my off-hours in 2004. It originally had all sorts of sounds, like clicks and whirrs and the blasts of air blowing through the tunnels, none of which survived the screen snipping process.