A simple yet complex tower defense game that is hard to put down.
+ In general I'm not a real enthusiastic tower defense gamer like some people are, but after playing Defense Grid for awhile I found myself really enjoying the experience. Defense Grid is simple enough to pick up and learn within the first few missions but still offers a lot of challenges for hardcore tower defense lovers.
Your main goal is to place towers that will destroy the aliens that walk across the map. These aliens are trying to steal cores which are located at another part of the map. You have a number of different types of towers to build and each has their strength and weakness. They also have a unique stat for attack power, rate of fire, and range. Each tower can be upgraded to a level 2 or level 3 tower which provides even more power. Also, you can sell a tower at any time.
What is nice about these towers is that they take no damage and have unlimited ammo. This may sound easy, but the real challenge is to manage your resources so that you can build the right kind of towers at the right places to kill all the aliens before they steal your cores. You start off with a set number of resources and over time you slowly gain more resources (and the more cores that are still safe the faster these resources increase).
Another feature of the towers is that if you place them in the proper slot then you can redirect the enemy path. This becomes an important strategy later where you want to increase the alien path length and expose them to your towers for a longer time before they reach the core.
The one big thing that I liked the most about this game was how it handles time. Every few waves or so there the game initiates a checkpoint. If you ever find you made a huge mistake you can always hit Backspace and go to the previous checkpoint. This offers a lot of forgiveness which I found to be very helpful, and it also promotes trial and error (something that is inescapable in a game like this). The only problem becomes if you find yourself in a loop that you can escape from but you just keep loading the checkpoint and failing again (in which case you have no choice but to go back two checkpoints). Likewise, if you think you are prepared enough you can press and hold F to speed up time so you don't have to wait for slow enemies to spawn. This is more of a convenience than a gameplay feature, but I really enjoyed it.
After you beat a level you can either earn a bronze, silver, or gold medal depending on how efficiently you protected the cores and maintained your resources. Also, after you beat a level you unlock a number of challenges for that level as well.
Story/Presentation: 3/5
+ I thought that the narration from your friendly AI was pleasant and humorous but overall I wasn't really enthusiastic about the story. You hear a brief snippet of story at the start and maybe another few lines at the end, but then while you play the level you forget what he was saying and focus on playing the game. The story takes a back seat in my opinion. And while it is there to tie things together, I just thought that it wasn't enough to be memorable.
Graphics: 4/5
+ From the standard camera angle everything looks pretty good. The animations and effects are beautiful to watch, especially when you have a successful layout and can just sit back and watch for a few minutes. If you zoom in you start to see the rough edges of everything, but there's really no point in zooming in since it doesn't help you play the game. So if you stayed zoomed out then you'll enjoy the graphics.
Value: 4.5/5
+ For $10 you are getting a lot of game here. I think I've played about 16 hours so far. Granted, about 4 of those were on the last level trying to find a way to beat it without losing a core. But there are plenty of levels that will keep you preoccupied for awhile. And I really didn't even try the challenge maps or the bonus maps. This is just the main story. Even after you beat the main story, you can go back and try to get gold on all the levels, or even try to get gold on the challenge maps. There is also a leaderboard for each level so you can compare your scores online and try to beat your friends if you really enjoy that. If you are a fan of tower defense games then there's no reason to not play this game. It's definitely one of the better ones that I've ever played.