Factorio is freaking amazing and is my goto game. I've just gotten into the multiplayer aspects and it's completely rekindled my love after 1400 hours of game-time (according to steam, far bit of afk here to be honest). There are train worlds, mod worlds, pvp worlds, so many new and unique ways to play. One of the best parts of this game for me has been that both the depth and speed of it are totally up to you. Although many people simply try and speed run rockets or automate their factory, this is all completely optional. You can create works of art, music generators, blinking lights, even straight up computers!
One of my recent side projects has been building out a modded multiplayer server that allows me to sell plots of land to players. My idea is to create a city of player-owned museums and shops, all with the backdrop of a custom story narrative in a high-end designed mall of sorts. My inspiration for doing so has been from watching first person videos of people walking in Japan, wanting to experience that but being unable due to the lock-downs. My favorite aspect has been creating an in-game 'paid' train line that lead the player out of the dense concrete shopping district and into one of the beautiful blue and green tree parks, the visual switch-up makes the experience fantastically enjoyable. I'm not really sure I'll end up making any real income from it but the process has been a complete blast. Playing the game in this fashion feels the same as Minecraft did, just with more automation and potential for world building.
Although not strictly Factorio related, something else I've pursued within the game has been setting up a semi-interactive self in my room. I have a few small monitors all linked up playing, and I just set my character to hang out in various places online. One game sits in a train-world just cruising along, another sits in a beautifully animated forest, another still hangs out on a pristine beach that I found. Sitting inside a small room day after day due to the pandemic has been brutal but this setup has greatly improved my sense of connection to the outside. Apart from getting to look over and see something that is visually appealing (and green now that bleakness of winter is here), I'll occasionally see random people join a server and become friends trying to build something together, it's awesome! My shelf has become an interactive, aquarium, IRC, hybrid, all thanks to this game.