You have 3 days time to work on your game any time. The challenge is to make it in 3 hours. Check the video and read the description, maybe it will be clearer!
the 3 day submission period is to insure that even team-members in different timezones can work together and that as many people as possible can enter/have time to submit! The idea is however to challenge yourself and complete something within 3 hours (of work/person) but stuff like "The time for coming up with an idea, making a design doc, compiling the game, publishing it, etc. does not count in the 3 hours" so keep that in mind!
