In a Balanced L-System, there are equal number of + and - in each rule. It makes more sense because one can translate it into a broken line and the rule is essentially "replace each segment with this broken line". F=FF+ is not a BLS; F=+F--F+ is.
What is the shortest Balanced L-System for the fractal produced by F=FFF+? I only got to F=F+F+F--F+F+F--F+F+F--.