Good
Well, game is pretty awesome to 70 level, when u actually can kill something with your guns alone. But after somewhere like 75, enemies get some kind of boost and are pretty hard to kill and after 85 - it is impossible to kill even ONE enemy alone. Thus, it is in the end defense game only after certain level, though weakened foes (usually flying ones) can be dispatched easily with shotgun. Game can be left alone after you upgrade everything and build everywhere - it runs alone very good xD Still, amounts of cash you have later on (200k+ after lvl100 and up) are just wasted, no more upgrades or anything can be bought. I suggest, after finishing 70lvl, add some extra hardcore weapon for character and some uber upgrades for sentries and floor panels. Also, additional bosses would make game a lot more harder than just leaving it playing itself. This would make game a bit more attractive I guess. Overall, very good game beside being monotonous after 70lvl (no additional bosses, no upgrades, no weapons), 9/10, 5/5