The wheelbase and overall length have been stretched versus a standard Fortwo. The Forstars is also slightly lower. This, combined with the fully transparent roof, gives the Forstars a low, speedster profile.
The Fourstars actually seems like it would be a fun electric city car. Sans the projector gimmick, the colorful interior, and the clear roof, and I think this is a pretty good indicator of what we should expect from the future of Smart.