  The real sphere $S^{N-1}_\mathbb R$ appears as increasing union, over
$d\in\{1,...,N\}$, of its "polygonal" versions $S^{N-1,d-1}_\mathbb R=\{x\in
S^{N-1}_\mathbb R|x_{i_0}... x_{i_d}=0,\forall i_0,...,i_d\ {\rm distinct}\}$.
Motivated by general classification questions for the undeformed noncommutative
spheres, smooth or not, we study here the quantum isometries of
$S^{N-1,d-1}_\mathbb R$, and of its various noncommutative analogues, obtained
via liberation and twisting. We discuss as well a complex version of these
results, with $S^{N-1}_\mathbb R$ replaced by the complex sphere
$S^{N-1}_\mathbb C$.
