Thank you so much for the feedback....as you have seen, it is possible for one missile to blow up more than one enemy missile, but it is difficult to judge it correctly as it is quite a tight range. I experimented with the radius, and struggled to decide between making it too easy and too hard...I don't know what the correct answer is to be honest, as I think while some people will want it one way, others will disagree....I have considered reducing the radius as the player goes through the levels, or maybe having options in the menu screen for "easy" or "difficult" games. I like the idea of showing the High Scores as an option in the menu and will definately include that in any update I do.
The criticism is really welcome - I am so new to this and have a lot to learn, so ideas like yours really will help me....thank you.