inspiration can come anywhere, from anything or anybody. While LG's Senior Research Engineer Sebastian Hochan Song was driving in a car with his younger sister and nephew, the windows on the car fogged up. Watching his nephew draw on the fogged-up window from the rear-view mirror, it looked to Song as though his nephew was drawing on a transparent layer over the background of the outside. It was as though he was drawing on two layers and the engineer could see both of them at the same time. With this, QSlide was born.
While LG was able to make the second layer appear right away, controlling the level of translucency was difficult, according to Song. But the concept has been perfected and it is now one of the new features on the LG Optimus G.
source: YouTube via AndroidAuthority