Competitive entrance examination into engineering school: Microsoft Surface replica (multitouch table at the time).
After studying the technology behind this table the most important part has proved to be the multitouch surface. It works as follows: multiple DELs are arranged at the edges of an plexiglass sheet and laws of refraction prevents the light from going out until a finger is laid on it, then becoming a secondary light source and being seen by a webcam under the sheet. By using infrared LEDs only a webcam can see the finger and neither the system nor the user is disturbed.
Once the assembly finished a software processing the webcam input was able to recognise the finger positions on the surface. A human interface driver find on the Internet allowed to take control of Google Earth using two fingers.