Rhindon Thanks, your words give me some hope! Oh, I had lots of ideas to complicate it but then decided to stick to a simple approach and keep it minimalist. With powerups and such, it became a shmup and less of a puzzle.
I had coded in a additional challenge, ie. When the background colour changed and it matched a shield colour, you can fire through that shield! But again it doesn't add much while detracting from the minimalism.. so the current version just has changing bg color but no code to deactivate shield. I might add it in a future update.
Ideally these endless games should be extremely simplistic so they appeal to a huge audience.
ps. Post your top scores, I'd like to see how well others do. Also, in particular, girls and how well they are able to play this game. I find they do not cope very well with all the fast moving objects. I have yet to have a female player past a score of 14... not kidding you, this is after many friends tried it, they are awesome at Candy Crush or matching puzzles but fail hard at this one.