I have to note that I received this game for free from a promotional SEGA event.
The game is a top down arcade shooter. Gameplay is pretty smooth. The story is nothing to write home about (mediocre at best and not very engaging). Upgrading is kind of a big deal and takes quite a lot of time. Multiplayer is fun if you've got friends into these types of games. Overall a pretty good game if you just want to mess around for a few hours now and then.