Well, as for Croatian, there is no need to even think about it, because we don't have a single number that can be written only with straight line segments

(JEDAN, DVA, TRI, CETIRI, PET, SEST, SEDAM, OSAM, DEVET, DESET)
Same goes for Serbian, and for Bosnian-Montenegrian variants. And for Macedonian.
Almost same for Slovene, only one number is made of straight lines - ENA (one) and it doesn't work.