I know JavaScript/jQuery quite well,
At:
http://www.torfl.eu/36/puzzle.html
I created a game but is not attractive, well I want to implement additionally to click&move the Drag&Drop(Move) event, so when you drag: i) a letter icon or yellow icon to: ii) a yellow icon or letter icon, then interchange places located, and vice versa, so esay to solve as a whole...

Any tip to start implement this Drag&Drop(Move) functionality (road map)?

Do you know any similar sites do this?