Undertale was made mostly by one guy (Toby Fox) (not his real name) in GameMaker in a bit over two years, so adjust your expectations accordingly.

It's a somewhat short action-adventure game posing as an RPG, whose trailer says that nobody has to die. So... not to spoil or anything, but you're gonna want to leave some of the NPCs alive, or most of them, or every single one of them, to see what happens. That's the gimmick. Not killing people. You can murder them in another playthrough if you want, the game has both options covered. Game saving/loading is also a plot point, so whatever you try first, your choice(s) will probably be referenced on your next attempt. This feature blew a lot of minds back in 2015.

The game mostly relies on its writing to keep the player interested in not just killing ♥♥♥♥. It is full of humor, although said humor is of the quirky, whimsical variety, bordering on nonsensical at times. The humor is visibly influenced by internet culture, although it does not straight up reference stale internet jokes. As an example: at some point in the game you are likely to face an enemy that is an airliner wearing an odd bonnet. Upon closer inspection, the airplane seems to like you, but when it talks (and it does talk), it denies having any feelings towards the player, and calls them an "i-idiot". This enemy is called a "tsunderplane" in the game. It is a reference to a certain trope in Japanese works of fiction, called "tsundere" (popular on the internet), and a play on words since the "ere" in "tsundere" sounds quite like "air" in English. Hence, tsund-airplane. If this example of humor (before it got ruined by my dry explanation) provided some amusement to you, then I recommend that you try out the game. Don't be distracted by its ugly-as-sin graphics, you will probably like it.

In fact, Undertale is barely a game. It has very rudimentary mechanics, mostly turn-based combat, where your only options are whacking an enemy with your weapon, or trying to do something to make them stop attacking. It is rather tedious, but made slightly more bearable by playing a very short (usually no more than 3-5 seconds) minigame during the enemy's turn, where you dodge their bullets by moving around on a small 2D playfield. Every enemy has a unique set of patterns, and they overlap if facing multiple enemies. There are also bosses, and every one of them adds an special twist to their fights. Whichever approach you pick (violent, non-violent, or running away), battles are typically over before too long. Unfortunately, enemies you made peace with will keep coming back to harass you, even if they're the type you've already seen. There is usually only one way to "spare" them (not counting the almost universally effective way of beating them within an inch of their life and letting them go), but at least you can typically flee from the fight after one or two turns. On the other hand, killing enemies will eventually exhaust their population in an area, meaning you will no longer be bothered by random encounters after some grinding, which is nice.

The soundtrack, also composed by Toby, is the strongest point of the game. It ranges from mediocre to very good. All in all, the game is worth the ten bucks, but only if you like the writing. Merely killing everyone is not very fun, because of the way combat is implemented. Be sure to play the demo first before making a purchase.

Undertale was made mostly by one guy (Toby Fox) (not his real name) in GameMaker in a bit over two years, so adjust your expectations accordingly. It's a somewhat short action-adventure game posing as an RPG, whose trailer says that nobody has to die. So... not to spoil or anything, but you're gonna want to leave some of the NPCs alive, or most of them, or every single one of them, to see what happens. That's the gimmick. Not killing people. You can murder them in another playthrough if you want, the game has both options covered. Game saving/loading is also a plot point, so whatever you try first, your choice(s) will probably be referenced on your next attempt. This feature blew a lot of minds back in 2015. The game mostly relies on its writing to keep the player interested in not just killing shit. It is full of humor, although said humor is of the quirky, whimsical variety, bordering on nonsensical at times. The humor is visibly influenced by internet culture, although it does not straight up reference stale internet jokes. As an example: at some point in the game you are likely to face an enemy that is an airliner wearing an odd bonnet. Upon closer inspection, the airplane seems to like you, but when it talks (and it does talk), it denies having any feelings towards the player, and calls them an "i-idiot". This enemy is called a "tsunderplane" in the game. It is a reference to a certain trope in Japanese works of fiction, called "tsundere" (popular on the internet), and a play on words since the "ere" in "tsundere" sounds quite like "air" in English. Hence, tsund-airplane. If this example of humor (before it got ruined by my dry explanation) provided some amusement to you, then I recommend that you try out the game. Don't be distracted by its ugly-as-sin graphics, you will probably like it. In fact, Undertale is barely a game. It has very rudimentary mechanics, mostly turn-based combat, where your only options are whacking an enemy with your weapon, or trying to do something to make them stop attacking. It is rather tedious, but made slightly more bearable by playing a very short (usually no more than 3-5 seconds) minigame during the enemy's turn, where you dodge their bullets by moving around on a small 2D playfield. Every enemy has a unique set of patterns, and they overlap if facing multiple enemies. There are also bosses, and every one of them adds an special twist to their fights. Whichever approach you pick (violent, non-violent, or running away), battles are typically over before too long. Unfortunately, enemies you made peace with will keep coming back to harass you, even if they're the type you've already seen. There is usually only one way to "spare" them (not counting the almost universally effective way of beating them within an inch of their life and letting them go), but at least you can typically flee from the fight after one or two turns. On the other hand, killing enemies will eventually exhaust their population in an area, meaning you will no longer be bothered by random encounters after some grinding, which is nice. The soundtrack, also composed by Toby, is the strongest point of the game. It ranges from mediocre to very good. All in all, the game is worth the ten bucks, but only if you like the writing. Merely killing everyone is not very fun, because of the way combat is implemented. Be sure to play the demo first before making a purchase.