Thanks for the help guys. I've now successfully got my thruster sprites attached (although I couldn't figure out the container option).
However, now after I click on an enemy sprite I've added sprite3.destroy to destroy the thruster sprite when the enemy ship is destroyed. The problem is this destroys every instance of sprite3 on the screen?
Capx is here.
Also, would you have any tips or tricks to make this a viable commercial option? First game so any advice is appreciated! I'm adding music, sound effects, and replacing the green ground sprite with a cityscape. And will plan to sell it for free, with in-app purchases.
Thanks heaps!