1. A computer implemented method for calculating a game score to create a ranking in a game, the method comprising steps of: receiving a request to create a first scenario in the game and one or more conditions regarding the first scenario from a first client computer; analyzing the one or more conditions; creating the first scenario using the one or more conditions; receiving game play data of the first scenario from a second client computer after a player of the second client computer plays the first scenario, wherein the game play data includes information of the player, result of the first scenario and play time for the first scenario; calculating a game score of the first scenario using the game play data; updating total game score of the player by adding the game score of the first scenario; and creating a ranking of players in the game considering the updated total game score of the player.