It might not yet be the phenomenon that is Wordle, but for hundreds of thousands of players, Digit Party has scratched the itch of a casual brain teaser to break up their day.

Players arrange numbers on a 5-by-5 grid, earning points whenever identical numbers touch on adjacent or diagonally connected squares. They can then compare their score to the puzzle’s maximum score that the game spits out at the end of a round.

There’s just one problem: The game was lying. Or rather, its creators were. For more than three years, Vincent Vatter, Ph.D., at the University of Florida and Robert Brignall, Ph.D., at The Open University in the United Kingdom didn’t know how to calculate the true high scores.