Talk about a small-scope but high-impact project! This one is a bit less on the serious side, though. A family member of mine was big into the game Clash of Clans in 2017, and had built a half-dozen sheets in Excel to help him track his progress and optimize his unit production in the game. When we looked at it together, the process of doing it with a spreadsheet was cumbersome and difficult, so we thought, "Hey, why not turn this into a specialized calculator?"
With a bit of context on how the game worked (maybe more than "a bit"—I've never played the game), we were able to turn the sheets into a functioning and pretty decent-looking (if I do say so myself) calculator, allowing you to pump in the amounts of units and resources you have now, and how many more resources (and how much time) you need to get to your goal.
The site remained under heavy use for a short period after launching at the end of 2017, by friends and others who heard about its purpose. However, as people using the tool stopped playing the game, word stopped spreading and the traffic for the site hit zero sometime in late 2018. As a result, it has been archived here as commemoration.