  We study a model of programmable matter systems consisting of $n$ devices
lying on a 2-dimensional square grid which are able to perform the minimal
mechanical operation of rotating around each other. The goal is to transform an
initial shape A into a target shape B. We investigate the class of shapes which
can be constructed in such a scenario under the additional constraint of
maintaining global connectivity at all times. We focus on the scenario of
transforming nice shapes, a class of shapes consisting of a central line $L$
where for all nodes $u$ in $S$ either $u \in L$ or $u$ is connected to $L$ by a
line of nodes perpendicular to $L$. We prove that by introducing a minimal
3-node seed it is possible for the canonical shape of a line of $n$ nodes to be
transformed into a nice shape of $n-1$ nodes. We use this to show that a 4-node
seed enables the transformation of nice shapes of size $n$ into any other nice
shape of size $n$ in $O(n^2)$ time. We leave as an open problem the expansion
of the class of shapes which can be constructed using such a seed to include
those derived from nice shapes.
