We would have done the project faster but we have the end of the school year and a lot of tests

Don’t worry this is not going to be the last $100 Game Jam.  We’re going to keep doing them every month.  If you miss this one there will be another.  Subscribe to stay up to date!

How long should the game last?

doesn’t matter.  The games rating criteria is in the description.  Length isn’t one of them.