Diadas: Based on the last dates of the comments, I am not sure if you still check for new comments. However, I quite like what i see so far. I might suggest that you add some way to tell what enemies are coming next. That would help players decide the next tower to upgrade. Also some way to deselect towers would be useful too. That way you would not accidentally place a tower you do not want.
Simple yet fun. A good game to burn time with. I would maybe adjust the cost and effects of the upgrades but otherwise I like it.
Also; @ Timster4800: Some people like to listen to there own music while playing these online flash games. It is unnecessary to call people 'retards' just because you cannot grasp a concept.
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