One of the best "Defend Your..." games around!
I got to level 27, had Maximum Gun Power, Maximum Autofire, 100 Shield, and Charge Blaster; and I never once got hit. Which meant it was relatively easy, or I was really good at it. However, when I reached level 27, it claimed to be "101.4% OF TRACTION/FIRING REPAIRED" "-1.40000000000003% OF TRACTION/FIRING INOPERATIVE", which either means that it was glitching, or I went too far. XP
Great game!