There is a collection of 'n' balls. Each player chooses one fixed positive integer(under the given constraints) that doesn't undergoes any changes throughout the game.

To make a move, a player has to take balls equal to the GCD(also called HCF) of the number chosen by him and total number of balls left in the box.

The players take turns to move and a player loses if he/she fails to take out the required number of balls. (i.e the collection has strictly lesser number of balls left than one needs to take). And, yes beware of time when you play in single player mode.

Okay. So, in your minds right now, there might be a hell lot of confusion. But, chill. Brainstorm your mind by trying your hands on the game. After a few tries, you will definitely enjoy! If you are a Sudoku player or a random mathematics freak, then this is something that you will surely love.