Green goo balls can detach from your goo structure and be placed where they’re needed. You first encounter these balls in the level “Tumbler.” They come in handy because the map rotates, but the pipe doesn’t move with it, so you need to have a tower built straight up to reach the pipe before your tower falls due to the rotating stage. Green goo balls can be picked up from any distance and dragged without being connected to the goo chain.