A challenge faced by the designers of these sets is that they are not able to work with the full palette of Lego bricks and colors ever produced when designing. Instead they are limited to the bricks and colors currently in production by Lego at the time of the product design. As an example, for Café Corner, the designer wanted to include a bicycle piece in the set, but at the time, the machine that made bicycle pieces was broken. It had to be fixed in order for the designer to be able to include the piece in his design. With Market Street, the fan designer was limited to only the bricks and color combinations available as 'active components,' meaning bricks that were already in production. No new bricks could be introduced.
