I'm not actually sure if it's that obscure, but I certainly don't hear anyone talk about it as much as it deserves to be talked about.
Vessel is probably the best physics-based 2d puzzle-platformer I've played. I first came across it when I was like 12, as a free copy of it was included in the gaming magazine my brother was subscribed to at the time. I didn't get too far into it as a kid, because the game sorta required a basic knowledge of the English language to get past a certain point (and I'm Hungarian), but still, I kept the name of the game in my mind, and now, 8 years later, I decided to come back to it.
This game is amazing. The main idea is that you are this scientist guy who invented these weird water-creatures called fluros, and now all factories and machinery utilize them for basically everything. But then, predictably, they start mutating and causing all sorts of problems that you have to investigate and fix. There is more to the story, but I don't really wanna spoil it, so I'll just leave it at that. It's genuinely pretty well written.
The puzzle design is fantastic. It's rare for me to come across a game like this, where every new puzzle feels like it's actually trying to teach me some new way the games mechanics can interact with each other, instead of just giving me a slightly different version of an earlier puzzle. And speaking of mechanics interacting with each other, one of the best parts of this game is how the fluros interact with each other and the environment in such a way that is predictable (because of their deliberately predictable behavior), but somehow *lifelike*. In parts, this game feels like you are disturbing the neural processes of an organism that just uses a factory as its host.
I could go on about this game forever, I didn't even mention the art-direction which is also great, and how the music, even tho there are only like 6 tracks or so, never gets boring and has this industrial Nine Inch Nails-esque feel to it, and-
Okay I'll stop. The game can be found here: https://store.steampowered.com/app/108500/Vessel/