It was a bug because when the energy is lower,
Blupi dies immediatly but the wall is terminated
with the death. It makes no sense because the
wall and the tower needs a lot of energy and
in all cases the death of Blupi.
It's possible to lost a Blupi (render) when some Blupi are staying
around an object like tomatoes. With this workaround, the render order
is not perfect but at least the Blupi is visible.
