Baldi's Basics is a 3D puzzle horror game that satirizes 1990s educational games The player has to locate seven notebooks scattered around a school they belong to the player character's friend, who cannot retrieve so as to not be late for "eating practice". Each notebook contains three simple math problems, but starting with the second notebook, the third question becomes unsolvable. As the player continues to fail the questions, of which some are impossible, Baldi becomes increasingly aggressive, moving faster and becoming harder to avoid Baldi hears every sound that the player makes and chases them with his wooden ruler. As he moves, he smacks the ruler, making a sound to alert the player of the approximate location of Baldi If the player gets caught by Baldi, they are jump scared, resulting in a game over
The player may encounter other characters that can be used to their advantage or should be avoided, such as Principal, Bully, or Playtime. The Principal locks the player in detention for a short period of time, which increases with every visit, after breaking one of the school rules. Bully takes one of the player's items upon interaction, and if they have none he will act as a human barrier, blocking a path. Playtime forces the player to jump rope 5 times in a row Items are scattered around the facility, which the player can use to defend themselves For instance, the player can use safety scissors to cut Playtime's rope, temporarily preventing her from stopping them After collecting seven notebooks, the player has to find all four school exits to beat the game, without been caught by Baldi The original game features both a story mode and an endless mode; in the latter, the player must keep collecting notebooks until Baldi catches them
Other versions and releases of the game, such as Baldi's Basics Birthday Bash and Baldi's Basics Classic Remastered, include additional features such as randomly chosen items The latter game features a "Demo" mode, which blends the original with the elements from Baldi's Basics Plus
