I don't like the time extinguish, a game like this should not be a "try click here and there" one, it should be a "think what to do and read carefully" game.
Remove timing, but nice game
too easy and a little boring, 4th level without any difficult, nice the idea, specially for the multi-target-bonus, but try to evolve the game ... some ideas: many cannons that shots from much than one side of the screen, mobile base instead of steading, etc.
this is a simplified-electronic-copy of the classical game "Risiko", very popular in Italy and I think in the world, maybe best known as "Risk" http://en.wikipedia.org/wiki/Risk_(game)
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