Note: the blue squares are locked in place. The green squares will travel and will help/hinder you. Of course, there are some wormholes. In order for the plus or minus signs to use a wormhole, it must land on the ENTER square, not merely pass over it.
Most interesting: you can't tell at the beginning where the signs will unite.
There are 50 levels and at the moment I'm on level 44..