This is such a great video of Tyler MacCready (son of Paul MacCready, the famous aerontautical engineer). He designed a ‘walkalong glider’ which anyone can build. Even a kid could do it!
It explains a bit about aerodynamics and genius design of a paper/styrofoam airplane. He called it the Air Surfer and its magic is basically a very simple principle: controllable slope soaring. He was ten when he came up with the design for this awesome toy.