Since 1 month I have less free time and my game prototype progress slowly. But I have already implemented a basic energy shield that replenish slowly, an armor that can only be repaired on the main tower (think HP) and the destruction of the gunship.

I also experiment a few attempt to improve aiming (more accurate reticle, laser sign ...etc.)

I will upload my work when the new features will be OK.

I've uploaded my work about shield, armor and Gunship destruction. I have also improved the aiming with a laser sign and an enhanced reticle.
You can try the demo here: Online DEMO

I'm not completely satisfied with the actual result but I will temporary freeze my development on these features to focus on this event: a new feature in a weekend.

Interesting, but how about adding "locking on" shots and increasing their range? :p