The game's definition of a week is unspecified. It starts on a certain time and ends at that time exactly one week later. To qualify as playing the game, you must start a new game that is not the tutorials. To begin your cycle of weekly games, select one day of the week that you will always be playing. Start the game and choose any level you have access to that is not a tutorial. Get past the loading screen, wait until the warm-up time expires and enemies begin to spawn. After this happens you can safely exit the game. Repeat the process each week at the same time and same day for six months.