OK here is the screensaver.nut. It goes in the screensaver subfolder, and unzip the archive to put the graphic assets in the same folder.
This is my messiest template, but since anyone who wants to use it on a different display (16:9 and/or higher resolution) is going to have to get into it to tweak it anyway, I guess I will just post it. I know, it's a mess. But for 320x240 people it should work as-is.
So it's just 3 layers of parallax stars (dim/distant/slow at z=0, brighter/medium distance/medium speed at z=1 and streaking close/fast at z=2) moving left to right, with snapvids superimposed, moving slowly across the starfield are different speeds and y positions.
Now here is one of the trickier parts of this, but it's optional.
You *can* just use your snapvids with the screensaver.
What I did, however, was create 8 second long subclips of each game snapvid that highlights some action and (more importantly) includes some distinctive sound from the game, where possible. I included my Joust and Sinistar examples below. I put all these videos in a "flyby" subfolder of menu-art. (Naming them doesn't matter, just use something descriptive. The .nut just pulls at random order.)
I also applied an audio fade in and fade out, so you can hear the video get louder as it enters the screen and quieter as it exits. I did this with FFMPEG (using -af "afade=in:st=0:d=1,afade=out:st=3:d=3" -- you can adjust those parameters to your own eyes/ears/tastes).
Finally, because the vids are playing on a black background, and many of the vids (like Galaga) have black backgrounds themselves, I tried different methods of distinguishing the vids from the background. I tried white outlines, and it looked OK, but I finally settled on the bezel effect. I just used FFMPEG to render the videos with a transparent PNG that added the highlighting in the upper left corner and the shadows in the lower right corner. (Or you could change the background color to something like dark blue, if that works for the look of your set-up.)
Now this is all somewhat insane. Because if I decide to add a new game, I can't just pop in a new ROM and a Progetto snapvid. I would also need to make a new flyby for the screensaver (and for my title screen there is actually another snapvid subtype). So if you like adding and removing games from your system, you might think about whether this is a road you want or need to go down.
