What I mean by ‘nesting’: The cozy feeling of knowing a space, having some choice around where you spend your time, and having a sense of leaving a mark on the world (or just immediate environment). Could be a space shared with others or not. May or may not have direct mechanics that encourage this feeling. The act of filling a game space with yourself, without being too driven by compulsion from the game. (I feel like The Sims / Stardew Valley / Animal Crossing can be an example of compulsive nesting - “I must improve this space / progress” - but that's definitely something that is part of how I come to the game, and how I interpret the goals they set out)
Some examples for myself:
[UnReal World](http://unrealworld.fi/) - A very slow paced roguelike that's basically built around living in the woods, off the land. It has very minimal mechanics-based goal setting, so setting myself to the project of "I want to expand my cabin" feels like a investment in the space that I later see reflected back at me in the subsequent hours of play. My most progressed save definitely feels like a 'place' that I partly occupy.
FF14 - Managing to get a house (which is hell) with a group of friends, and gradually acquiring furniture is quite nice. The fact that many pieces are available to buy on the market board somewhat deflates my pride in individual pieces, but carefully arranging stuff in our house feels like it's my/our own, in spite of the commonness of the individual pieces.
Fantasy Life (3DS) - Has light Animal Crossing-esque home customization, all of the items for which are craftable by you or rewards for doing things in the world. Completely irrelevant to any mechanical progression, but the coziness of the world coupled with the ability to shape your own home makes that game feel quite a 'part of myself.'
Suikoden 2 - The castle development mechanics, thin as they are, are supplanted by the visual detail of the spaces and the time you spend traversing the different screens. Recruiting a new member and seeing how they key into a space feels like adding another personal touch to the game space.
Metal Gear Survive - in spite of the fact that it ultimately let me down, there was a good 3-5 hour period where I felt a nice spatial progression and hope about the base-building mechanics. There is a version of that game in my mind that leans in that direction, rather than the grind it in fact became.
[The Longing](https://store.steampowered.com/app/893850/THE_LONGING/) - Another super slow game, but gradually getting a sense of the layout of that space really makes me resonate with the Shade, and the customization of his living quarters only adds to that.
What are examples of games where you've found yourself filling a space pleasantly, feeling comfortable? I've never cracked into any of the first person Fallout games, but in my minds eye there is some space customization / sufficient time wandering the same areas to get a sense of really occupying the space.