buy it and if it snitches just refund before 2 hours lmao

check drm section on store page

I've put a lot of time into this and unlocked almost every achievement, but I still can't guarantee your answer. Steam's offline mode usually works for games without third-party DRM, but some single-player titles check in on launch anyway. Look at the store page's right sidebar for a DRM section; if it only lists Steamworks, you can set Steam to offline and test it yourself. Updates are another thing though, you need online to download any patch, no way around that. I won't promise you anything, because publishers are scumbags, but that's how Steam handles most of my library.