This Hand Controlled Tetris Like Game uses an Altera FPGA to captures a video signal and looks for a players hand skin color. The system tracks their hand movements and looks for the user moving their hands forward and back by determining how tall the skin colored object is over time. The goal here is to prevent the falling tetris like blocks from falling by rapidly pushing and pulling on them. If you want to use this as a starting point for your creation Tian Gao has documented the entire system here.
Thanks for sending this in Tian!