A well made game, however I found multiple problems which stopped me from playing multiple times.
1: All of the waves are hordes of enemies with varying speeds and explosive radius, this COULD have been used to create more strategy, but sadly it wasn't. In the later waves your shooting at a huge mass of enemies, with no indication of whether or not you could be doing better. In the end you'll just end up overpowered and lose, no matter what you do.
2: The upgrades are automatic, I like that you aren't cut off from the actin to upgrade your weapon, which can help in dire situations. But on the other hand you have no choice as to what your upgrade is, and the game, once again, could have had a bit more planning where you have to choose weapon options that work well together, but you have no choice.
This game had a good story line and music, but these issues hamper the replay value, still good work.