The game board in Quint-X, a.k.a. Katalon, features five interlocking squares, with one central square and one square at each of the board's four corners; each square features within it an X pattern of holes that mimics the layout of the squares on the game board.
On the first turn, a player places a marble in any hole, but from then on a player must place a marble in the square matching the position of the hole in which the previous player placed his marble. Within that square, though, the player can place the marble as he wishes. When no more empty holes lie within a square, then you replace an opponent's marble with one of your own.
To win, you either completely fill a square with your marbles, have a majority of marbles in three of the five squares when all spaces on the board are full, or have all of your marbles on the board at the start of your turn.