Héctor Corte

Man great submision. I have used it to make some geek gif in my blog.
http://thebrickinthesky.wordpress.com/2012/12/23/my-own-death-star/

Thanks for your comment John. I dind't take care of that kind of things before because It worked fine on all my computers and they have different Matlab releases.
I will make things better from now on.
I'm working right now on trying to avoid the use of Image Proccesing toolbox and on the use of globals.

Very cool game with an authentic retro feel. However I do have two complaints about it:

1. it may be a better idea not to write the code for keyboard handling in KeypressFcn. Because that way you would experience a delay (~0.5 s) after the first keypress. Instead, set a variable to true in KeypressFcn and false in KeyreleaseFcn, and check the status of this variable in the main loop to determine whether this key is pressed or not;

2. The bullets travel too fast. They usually go right through an enemy without hitting it. Possible solutions are 1) slowing down the bullets (less distance per frame, slower apparent speed), or 2) not slowing down the bullets, but increasing the frame rate(less distance per frame, same apparent speed), or 3) using better collision detection algorithm (same distance per frame, same apparent speed).

Anyway, I do like this game. Please keep writing more stuffs like this!

need to move intro() to after spaceship & terrain are initialized