What was your first “successful” project?

Successful meaning that it actually made a difference in the real world.

Mine was a console aplication that was drawing a moving graph of some parameters that were analised on a factory floor. It refreshed every 3 seconds, so it was kind of "real time". Before the parameters were only shown on the screen as a bunch of numbers and it took a long time for the worker to get the gist of them.

This problem was thought unsolvable for 10 years without upgrading the system (buying newer version of the software).

I made it in a console because I didn't know how to do anything else back then.