I have been waiting for a time attack on this game since I first heard about them and it seems no one is doing it so I did it myself, this is a long side scrolling action game composed of 7 levels, it has a wide variety of weapons that can be used alone or mixed for better damage-speed, it also has some bare hands attacks and even a combination move just like the special moves of one on one fighting games, there's also a space shooting level where you control a ship, i finished it in 33:04, there's little room for improvements unless you play with 2 players or controlling both characters at the same time (a bit difficult for this game).
Here's a link to the movie:
http://usuarios.lycos.es/amstradpics/gunstar.zip
(Right click --> save as or copy the url and paste it in your browser)
It was made using v8 of the modified Gens by Jyzero and uses the rom that has the same name as the movie.
If anyone has suggestions on how to improve the movie i'll gladly try them.