Never felt challenged, it's frustrating that it doesn't save your gene setup, good idea but poor execution. Also, did no one think about the dog fighting thing?
I rated this game 3 stars, here's why: It was too easy to get super powerful, the shop prices should be redone so it is more difficult to get high end gear. No noticeable effect from armor upgrades, with the highest hull and 4 of the best armor enhancements my life still drained just as fast as it did with a lesser hull and no armor. Levelling up should happen more, I finished the game at level 15 and I was nowhere near finishing the skill tree, leveling up more would result in being able to experience all of the skills and get a better feel of the full game. Bugs/Glitches, items disappear from inventory, guns not showing up in the shop preview, multi-gun rockets not seeking enemies. I liked this game but it quickly got tedious/boring and I could easily beat levels by staying in one spot.
The trick I noticed is that you can just put your mouse cursor over the tank firing a round and follow along with them (may need to lead them for slower firing rounds) and the round will go right back to them. Really takes the guesswork out of it and helps a lot in tougher stages.
 "Mutant Fighting Cup"){kind=icon}
 "GunBall 2: Emperor Revenge"){kind=icon}
 "Shield Defense"){kind=icon}