Call me a child, but I still have a love for Lego. Lately, as I have been sorting my childhood collection into individual sets, I needed a way to track how many of each piece I've found for any given set, and started programming a tool that lets me pull Lego set inventories from the internet and keep track of the parts I've found.
This is the first time I've found a problem and built a program to solve it, and it feels so good! :D

(in case anyone is curious, I'm building it in Java as an Android app.)