Horrible.
I loved the first 2 games. Lots of powers, upgrades, etc. This is an insult to be called a sequel. It was fun at first, but then it got worse and worse. The walls do WAY to much damage. Also, when I tried to air strike on level 7, It destroyed my sentry guns and ended the level. The tank was okay, but it was to huge a target to avoid anything, it was better to just sit still and fire away. There are too many buttons that are just not needed, many times I pressed E accidently and hundred of enemys got through. the fact you can't cancel early is a dumb, and it was to easy to push it when trying to avoid everything shooting at you. Point is, having lots of upgrades is nice, BUT KEEP IT SIMPLE.