Defense Grid is a tower defense game, and at its core it's about what you'd expect for a game in the genre. You have a resource to protect, an invader that wants to take the resource, a few paths that the invaders can use to get to the resource, and defensive towers that you can build to stop them. Defense Grid doesn't mess with this formula, which is a good thing because the reason you see so many tower defense games these days is that it's a fun formula. What Defense Grid does do is take the basics and build upon them. There are many different types of invaders, aliens in this case, and you'll need to deal with them in different ways from the game's expansive arsenal of tower types. The result is a fun and challenging tower defense game which offers a bit more strategic depth than typical.
