Level 23 is stupid hard. Pretty much all of the other ones have multiple possibilities, but there is such a ridiculously small margin of error on 23 that it is essentially impossible to get gold.
The good news is, that's the only impossible level I'VE come across!
Editing my flat goes fine until I place my beta poster, and then the buttons freeze. Can still slide the view around, buttons still highlight, but clicking does nothing.
 "Gravitee 2"){kind=icon}
 "Fantasy Avatar"){kind=icon}
 "Remnants of Skystone Beta"){kind=icon}