http://undertale.com/

I discovered it completely by accident, as YouTube started suggesting me random songs from the soundtrack.

I spoiled most of the story for myself before I even played it, and I still love it.  I've never seen a game play with the fourth wall quite the way this one does: It never technically breaks it, but merely shifts it.  It's hard to explain without spoiling anything, the best I can describe is similar to the way Homestuck treats the fourth wall, by moving the goalposts.  It also takes a lot of inspiration from Earthbound.

Depending on your playstyle--you can either go pacifist, genocide, or anywhere in-between and the story actually changes depending on which route you take.  Which is very refreshing, in most games with this kind of mechanic the difference between the "good" and "evil" paths is mostly superficial.  This actually makes you deal with the consequences of your actions, and it's awesome.

To quote one of my favorite streamers, "Go play this game. Stop whatever you're doing and play this game. Stop watching my stream and go play Undertale right now." It's the kind of thing that's been rated up with the likes of Final Fantasy 6, Portal, and Cave Story.

You have the option to kill every enemy you encounter, but you also have the option to save them. It's a relatively short play, but you'll want to play through it multiple times to get the whole story. You can also befriend many of the bosses after their battles, which gives you even more story.

Just... Stay away from the more rabid parts of the fandom, whatever you do.  The game seems to attract a lot of annoying SJW types for whatever reason...

looks nice. If only I had time...

I got gifted this game by a good friend. Finished it once so far (neutral route), and I was in the process of finishing the pacifist route... when my main computer broke down. I can't finish it now and have to be really careful not to be spoiled. (For some reason, the Undertale wiki on Wikia is REALLY happy to spoil things for you...)

It's a wonderful little game.

I've started playing it a few days ago and thought it was good, but I don't see a reason for all the hype.

Most people don't the first time they play - I watched a spoiler-tastic review on YouTube a while back and he said the same thing, then he restarted to play "on the game's terms" so to speak and it clicked.

The game is specifically designed not to give up all of its secrets on the first playthrough; in fact you're actually locked out of getting the best ending the first time around regardless of what you do, so to truly win the game you have to restart, and that's when the charm really shows.

I'll give you a hint though: The game knows when you're save-scumming without ever breaking the fourth wall, and that's where most of its charm comes from.

I'll be the first to admit the game is probably overhyped, but some of the hype at least is deserved.  It's playfully subversive, and that's what makes it refreshing. (Unfortunately a good chunk of the fandom missed the memo on the "playful" part...)

Hm... But is there any reason to save-scum on this?
I've only played it for a little over an hour so far, so I may be missing something.