Garden of Coloured Lights is an old school 2D vertical shoot-em-up with some innovative elements. Innovative graphics, soundtrack and game concept. The game itself is very challenging and as you progress, you will understand that you are dealing with a true piece of art... It is free, open source software. It is released under GNU GPL license v3 which means that it is not only free of charge, but you may also download the source code and play with it.