Happy Setember! No, that’s not a typo, PlayMonster is rebranding the month to celebrate a popular game’s big birthday.

All month, it will celebrate the iconic game Set with #SETSundays, when PlayMonster’s social media will be dedicated to solving the puzzles. In addition, every day a new puzzle shows up on this website, where people can head to solve it.

Marsha Jean Falco first thought of the game in 1974 when she was studying the genetics of animals. Falco used file cards with blocks of information to keep track of each animal and used symbols to represent them. One day, while sharing the info with a veterinarian, they asked if combining the symbols would make a set — and the rest three decades of history. The game officially went into puzzlers’ hands in ‘Setember’ of 1990.

Players have loved the mind-exercising game since then as it bridges education and fun. It’s sure to be around for Setembers to come.