I should confess that since 2007 I no longer play video games, if I know about this or that game being the flavor of the month is mostly through osmosis and thanks to youtube longplays sometimes I dwell in them as I still see those as a cultural product and not only a mere entertainment even (like in contemporary cinema and literature) there is plenty of commercial garbage.
Undertale caught me off guard, at first I thought it was just a project fueled by the nostalgia of those who enjoyed Earthbound in their childhood or young ones who re-discovered the game through the emulator community. Far beyond being a re-telling of the cult classic, Undertale is a metanarrative exercise which uses the well know tropes of the RPG genre for tell us a story about morality and ethics that put to shame what the developers of the Bioshock franchise attempted in said series. I am not going to talk about that aspect, which many had already mention already but the factor of innocence in the fairy tale merged with pop culture setting that constitutes the entirety of the game.
First of all, the game main plot is sustained in a very clear position: even with excellent nurture, nature can be a great obstacle in the rising of a child. Is obvious, if you pick the hints scattered through the game world, to tell that the first human child adopted by the monster's queen and king was a misanthropic sociopath, his deviant nature is the detonator of the tragedy which brings us strangers in a strange land a problem to fix (pacifist route)or made even worse (genocide route). Is this tragedy which makes the game mature, no matter if we obtained a happy ending by bringing the monsters to the surface, there is one character which status quo is unbreakable as well as the broken relation between the monster's monarchs. This is a very interesting element considering the "time traveling" nature of this digital adventure, during the game we are taunted if we use our "time travel" for do things which in other games doesn't do have consequences as a reminder that we can't really fix everything in this world as if we were facing a classic Greek tragedy.
What would happen to Oedipus' story if he could "load his game" before killing his father once he knew the truth? Most certainly the plague that scourges the city-state of Tebas would never happen as the gods will not be angered about Oedipus sin of marrying his own mother. Still there is going to be the awareness that Oedipus did that in another timeline, which means the tragedy is somewhat there even there is no true catharsis as its conclusion doesn't become the status quo, making it impossible for be a good dramatic piece as exposed by Aristotle or Nieztche. This is not the same concerning video games, as we are experiencing the story by an avatar, the actions are made by us and not by a third party, so at some level we interiorise them. This interiorisation of our avatar's action is the main source of the guilt a player can feel when reaching the conclusion of the genocide path realizes that he/she is the main villain of a tale which doesn't have any by becoming a monster's monster. We can start the game anew but there is an element which is going to remind us that we killed Toriel, and that precisely is the metanarrative element in the game which makes it perhaps stand over the cult classic its was inspired in first instance.
This aspect of the game could even be used for possible exercises concerning the topics of ethics and morality for teens in a teaching context. If philosophy was introduced into the high school curriculums of some countries, a teacher could use this game as a teaching tool concerning this topic (and even as an introduction to those linked to the concepts I mentioned earlier). This confirms one thing, that video games are finally reaching a maturity as cultural objects.