Oh. My. God.
This is one of the best defence games I have ever seen. It is wildly addictive, and I have actually seen an increase in my reaction time after playing hours on this game. Its so good, the repetitiveness doesnt even bother me (though that is why im giving a 9). One thing that bugs me is the lack of description of the different colour boxes and the rays they send out. Sometimes I think that they are actually good instead of bad. You should add a descriptions/instructions page next time. Overall, GOOD JOB!