Into the Breach would work. You can turn off the game at any point and come back to it, thanks to it saving after every turn. Plays a lot like chess, with different abilities and enemy types to keep things interesting. Highly recommend!
Bit of an oddball suggestion, but you might want to give Metro 2033 a try. It takes a bit, but you can eventually obtain a stealth suit that has a light meter akin to Thief, and you have a pneumatic rifle that shoots silently. Spent so much time skulking through levels trying not to alert anyone the entire time, had so much fun.
I feel like Valve is also just full of the type of nerds that want to fix bugs, regardless of profit motive. Proton is as much a passion project as it is an answer to Windows.
Also incidentally comes as a phone app with your Netflix subscription!