A Safe Purchase
Defense Grid is a tower defense game. I could probably end the review right here and most people would already know the experience. You build towers with guns. Aliens attack in the deadliest form of offense known in the universe: a slow peaceful parade. They die, you get money, towers get upgraded or reinforced, and repeat until the waves of aliens stop.
Compared to Plants vs Zombies, Defense Grid is much truer to its simpler brethren found all over flash sites. It's streamlined and well made with the exception of some slowdown. Unfortunately, as the game progresses to its later levels, it becomes tedious. The maps start getting more complex sometimes making it hard to see the "flow" of the enemy units. If you're a bit of a perfectionist, you'll be restarting constantly as one bastard slips right through your defense.
It's damn fun though in small chunks, and the main narrator, a raspberry loving British fellow, manages to be quite a good character. His constant reminiscing of past events, lost battles, and dead friends adds a sense of weight and responsibility to the story and the levels. Story may be strange to have in a tower defense, but it's there and it works for as minimalistic as its presented.
All in all, it's a safe purchase for what it is: a solid tower defense game and nothing more.