  Given a shifted order ideal $U$, we associate to it a family of simplicial
complexes $(\Delta_t(U))_{t\geq 0}$ that we call squeezed complexes. In a
special case, our construction gives squeezed balls that were defined and used
by Kalai to show that there are many more simplicial spheres than boundaries of
simplicial polytopes. We study combinatorial and algebraic properties of
squeezed complexes. In particular, we show that they are vertex decomposable
and characterize when they have the weak or the strong Lefschetz property.
Moreover, we define a new combinatorial invariant of pure simplicial complexes,
called the singularity index, that can be interpreted as a measure of how far a
given simplicial complex is from being a manifold. In the case of squeezed
complexes $(\Delta_t(U))_{t\geq 0}$, the singularity index turns out to be
strictly decreasing until it reaches (and stays) zero if $t$ grows.
