The motivation behind this demo is that I had some difficulty understanding the algorithm, so to gain better understanding I decided to implement it. This is not meant for serious use, What I tried to do here is to illustrate visually how the matrix is constructed and how the algorithm works. Also I wanted to allow some freedom for the user to construct a custom path along the matrix and see how paths translate into alignment "or mis-alignments". The code is available on github and is released under GNU/GPL3. If you wish to contact me send me an email to firstname.lastname@example.org.