Damn... I wasted a bunch of time playing that game.. its quite fun..
Looks to me like its simply a really long layout/level the back grounds were simply repeating parallax layers.
The problem with space shooters is space is basically endless so you can't simply repeat the same cruise ship over and over like that game does on the beach scenes.
1. You can do it several ways, dynamically generate stars and heavenly bodies randomly that move on a black background using a bullet behavior.
2. Or you can use a repeating starfield background (this method is tricky as you will run into the white line issue of repeating backgrounds in construct2).
3. You can do like I did in my space shooter (linked in sig), I simply used a wiiiide .png and timed its speed to last until wave 100. Since my game wasn't infinite this works.
If your making a level that the player beats after going only so far then this would work for you too.
If you question was really about parallax layer behavior.. there are lots of tutorials and a manual topic explaining it using Construct2.