 LEDs were chosen because they were viewed as the lowest maintenance option of the possible color changing fixtures . LEDs fit into an electrical circuit , causing illumination by the movement of electrons in the <unk> material and making a filament unnecessary , so the bulbs never burn out and do not get too hot . <unk> were added to the screens to keep direct sunlight from hitting the LEDs . Color Kinetics ( now part of Philips Solid @-@ State <unk> <unk> , which is now called Philips Color Kinetics ) <unk> 12 LEDs fixtures are used to illuminate the tower structures and glass in an attempt to meet Plensa 's objective that the towers have a light and translucent appearance , with their internal structures reflecting light from behind the glass surface . The electronics were designed to be adaptable to the time of day , weather and season and to meet the desired century @-@ long longevity and <unk> objectives set by the design team in response to the thirty @-@ year directive . 
