CSI design- Whiilfly. Whiilfly is an innovative bike light brand- a totally new form of battery-free bike lights, which makes your cycling more care-free and sustainable. The name of Whiilfly comes from the idea of combining wheel and firefly and replacing the "e" in "wheel" for "i" . The end of the character "y" symbolize the shape and the form of the product on the bike.