TODO: Use  pygame.surfarray for surface manipulation
V0.5    November 2011
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Level stage redone and generated when the level info file changes. New explosions
Minibosses fully implemented
HUGE performance improvements
TODO: Add options to the menu, final boss, more levels


V0.4    October 31st 2011
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Added minibosses and bosses (still not implemented fully)
A small menu has also been implemented
TODO
The miniboss should fire lasers or something to the player's ship
Add options to the menu, music on and off, etc

V0.3    September 22st 2011
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More improvements

TODO
Add menu with difficulty, options (music on/off, fullscreen, etc)
Add several levels
Roadmap to 0.5, create end of level levels (bosses)



V0.1    June 21st 2011
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Initial version

TODO
Add menu with New Game and, maybe, new options
Add better collisions
Add subclasses of Alien with different damage
Add image for the background with walls
Add levels read from gif files
Add gameover


Credits
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Explosions:
http://gushh.net/blog/free-game-sprites-explosion-5/