PataNoir is a detective game based on extended metaphors. The game is full of things that have (occasionally forced) metaphors applied to them, such as "his eyes are like a deep blue lake." You can interact with the metaphors like you would with actual objects, and dive in to the lake to see what is there.
Metaphorical things you find can be given to people to change their feelings about you or themselves. If you change someone's facial expression by applying a "warm" metaphor instead of a "cold" one, he'll be nicer to you, and that sort of thing. On the other hand, they can't affect the world otherwise. You can't cut someone with a figurative knife (but you can with the literal one). Switching around peoples' demeanor and the metaphors on objects are the only ways to really proceed in the game.
The game has an in-game hint system, and let me tell you, I leaned on it a lot. At first I thought the game was pretty easy. But later on, I found that the puzzles were kind of tricky and as the stakes raised, they got harder for me to figure out. That bothered me a little, but I'm not sure what the fix is. Between this one and "Earl Gr(e)y" two years ago, I'm convinced I'm just not good at this sort of wordplay style puzzle. I eventually resorted to the walkthrough so I could limp over the finish line in time to see the ending before I had to stop evaluating.
A really nice touch, if you finish the game, is that it implies that your character is just crazy, an unreliable narrator. I couldn't find much reference about the disease it claims you need medication for, but I only did a quick Google about it. My guess it has something to do with hallucinations, which is why you should be taking, but are apparently skipping, your medication.
Pretty enjoyable, that is, if you like wordplay and aren't burned out on noir by this point.