Spirit City: Lofi Sessions is an amazing focus tool. It's not really a game; while there are gamified elements, like acquiring different Spirits and buying different clothes or decorations with credits, the main purpose of it is to help you focus on whatever you need to.
You can either play built-in playlists from Lofi Girl and Homework Radio (although the Homework Radio ones are apparently leaving in August 2028), or play whatever you like on YouTube in the "external" player. I usually do playlists of Minecraft music, although I imagine you could even put on a video essay if you wanted to.
There are also various productivity features, like a Pomodoro timer, a stopwatch, a to-do list, a journal, etc.
Along with that, you can customize different kinds of ambient noise, some of which change the environment; you can choose different decorations and clothing items; you can bring the different Spirits you collect as companions, doing whatever activity you'd like. I've also bought all of the DLCs, which add even more Spirits, activities, and places to decorate.
I wouldn't recommend treating this as a game first and foremost. There aren't an overwhelming number of Spirits to collect, and though it takes a while to collect them, it's not a huge amount of time. It's just really nice to have a space in the screen that's my own, that I can customize as I like to help me focus. I think it might be even nicer if you have multiple screens, so you can keep looking back at your Spiritographer self, but I find it works fine with just the one.
This game also works with Proton for Linux, as that's what I'm using!
All in all, I would say this is an 8.5 out of 10. It's not perfect - some of the animations are a bit lacking and I wish the to-do list was more customizable, and that the stopwatch counted towards "focus time" - but overall, it's a really fun, good-looking, relaxing focus tool. Thanks very much for making it!!
