Haha, thanks so much. We were debating whether there should be a 'delivery point' SEPERATE from the filters, which would definately be easier to understand.
We to push for elegance (by having more multi-purpose pieces) but perhaps a bit too far. If you're stuck for a long period of time, it's usually best to reset the level because we couldn't find a way to make sure the situation didn't get 'dirtier' and harder to solve as you played :P