Of all the things I've made, and of the fewer I've published, the one that's always generated more questions is Domains.
For me it'll always be special, because it was the first programming project I did on my own (or at least with just code and and IDE, I did do some AppInventor stuff before). For context, the idea is simple: I made a competitive board game. The only twist is that players can't really be people (they can, of course, but the game is designed in a way that playing as a human is boring and kind of frustrating). What plays the matches is a player program sent by the human player beforehand.
There's an empty grid and up to four players, starting in a corner each. Every turn, players give orders to units, which are the pieces in this game. A player controls a few of these each turn. The objective is to get as many points as possible, which is closely tied to taking control of as much as the board as possible. For more details, go look at the repository.
For anyone that's participated in any algorithmic game competition, it's the exact same concept. The reason to make it, then? I really enjoyed the one I took part on when I was studying at university. Apart from that, I just like games in general, even making them, so I kind of came with an idea for a competitive board game for algorithmic players. I took part of the code we had from the university competition as a template and went off to build the entire thing.
It took about a month or two of spare time, and I remember the most difficult part was correctly painting areas after closing drawings or other events that could trigger painting. The game was in fact a bit buggy for a couple years, until I wanted to use it for a bigger project and had to finally fix it. However, the planning and OOP stuff was very straight-forward to me: I always say that our university -at least when I took those courses- was terrible at teaching Object Oriented Programming. If I can say I really got the hang of it it's because of this project I'm talking about here.
This little game has been on my GitHub profile the longest, and I can probably give it at least half credit for "passing" some job interviews for me. I would expect my first project to be more boring than this, but I'm glad to say that I'm still proud of it (especially after the latest fixes...).
This brings me to a different topic: I'm always been very reluctant to make these "practice" projects people use to learn some tech stack or language, such as web page clones, game clones, "calendars", "to-do lists", url shorteners...
Not even because they don't stand out to other people, I don't care that much about that, for me it's more that they don't bring any motivation out of me. I have to think that it's really cool to get on it.