Game modes (stock, time) function, display stats on client side, and
return isGameOver() when the end conditions are met. Time and number of
lives can be set for a game state using setTime() and setStock(). Mode
can be set using setMode(). The constat modes are GameState.STOCK,
GameState.TIME, and GameState.MENU. Menu mode will not end, subtract
lives, or give points, it's for pre-game menu levels.