Factory Fever plays in the warehouse of the Factory Fun factory. Instead of building the machines in your factory, now you must store the products in the warehouse, which is a very different task. What's more, you must store products of the same type in a group or have them connected by conveyors. These products are both dangerous and extremely heavy, so for safety reasons you must not drag them more than once, and all products of one type must be together. Building conveyors helps to connect similar products.
You know which products will need to be stored, but you don't know when and in which combinations, so you must anticipate the future by holding different good options for stocking the goods. The pillar in the middle of your warehouse is as annoying as it was in the factory (Fun) halls.
When your warehouse is finally filled, the game is complete. If each of the six different goods is stored in a single group, you are doing well. For one product that task is easy because you have to store that type of product only once (i.e., 1 tile). The very dangerous product you should place at the wall, and for the mixed product you decide at the end which product type it is. The conveyors should not have dead ends (to the walls or pillar). Each error results in 1 error point, so try to have the fewest errors.
For a new challenge, the B-sides of the boards get used. The player with the best score on the A-sides gets the hardest difficulty level B-side warehouse, and so on.