The Roomba gets messed up by very dark carpets becuase it thinks the darkness is due to a drop off. Even if you pick up the Roomba and put it on a dark carpet, it won't work. The trick to getting the Roomba to work on dark carpet is to put clear packing tape across the four edge sensors on the front of the Roomba. Once you do this, it'll then stop avoiding the dark carpet. But be warned, it will also stop avoiding drop offs. So if you have drop offs you may not want to try this trick on your Roomba.