1. I get the following error printed continuously in the console.
   ‘Failed to load image "assets/health-bar.png". Reason: Unable to open file’
2. Too bad there are no enemies… I like the retro feel of the spaceship and its propeller.
3. Reading the main concept, I am wondering if something specific was supposed to happen when the boss is revived? For example, is there a change in difficulty, pattern, or anything each time?

You can still update your file, so do not hesitate if you have something. :)

(By the way, just putting here that my game is pending until I get the submission form.)

PS: I see several DLL files with the sfml string, so, did you use SFML by any chance? :)