This resonates strongly with me. I've been working on my side project (which afaik I'm the only user of ... a text editor implemented in 65.2k C++ lines) for 9

This resonates strongly with me. I've been working on my side project (which afaik I'm the only user of ... a text editor implemented in 65.2k C++ lines) for 9 years and ... yeah, it feels like I'm playing a game. Maybe it's like I'm building my own virtual castle, where I spend a significant portion of my time. I come up with a new feature to add and the challenge of extending my implementation to support it often feels quite similar to solving a challenging new level in a videogame. I guess a meta point one could make is that I need to make sure I steer the implementation in directions that keep the game fun, so that (this being a side project) I'll continue to play in the future.