I now have experimental mechanics for moving, controlling the ball, shoving minifigs of the way.
I still need mechanics for shooting and passing the ball, kicking off and, er, dismantling minifigs.
If anybody wants to help, the doc is here: https://docs.google.com/document/d/1ldykFS1qRdWbrehW_WZDrYo18gzmmXnw7S0bP17mIsE/edit?usp=sharing . I have 6 days to fulfill my promise :)
Also, I apparently promised to call this game #legrick, so I guess that's the official name.