It's alright.
If you're looking for a game that is inventive, innovative and defines a genre, then this game really isn't for you. Defense Grid is a fairly generic 3D tower defense game, with few innovations. There really isn't much to differentiate it from most other tower defense games. That being said, it is well made, well balanced and quite addictive. It isn't a bad game, but it isn't brilliant either.
Gameplay-wise, it is a very well-made game. For a free game (or 400 Microsoft points now) it is incredibly balanced and fun. There are only ten towers that each can be upgraded twice, allowing for strategic use of resources gained by killing aliens. Each tower has it's downfalls but all can be very useful at times. The tower design isn't the most spectacular, as many are fairly basic ideas. Gun Towers, Laser Towers and Cannon Towers for example. The first couple of levels are fairly dull, which almost put me off, but I'm glad I didn't. Some of the later levels are impeccably designed, requiring the user to make a pathway for the aliens to help them. This works brilliantly with the level designs and makes it strategic and fun, but very challenging at times. Some of the last levels are devilishly difficult. Me and some of my friends have been hooked - it's such a shame there is no way to play multiplayer or a level designer so I can share levels with friends, however that would be asking quite a lot of the devs.
Graphically, there can be no complaints. Set in the distant future, Defense Grid illustrates a dystopian future beautifully. It isn't vibrant but the graphics are clear and are as good as some full console games that cost £40. This is a huge thing for a free game, as they usually rely on good gameplay rather than worry about graphics, but developers Hidden Path Entertainment have combined both well. The aliens, of which there are 15 different types, are detailed and their movement is smooth.
The game is not the longest, as there are only 20 different levels, however there is some replay value. There are different 'challenge' modes for each level that take time to master and complete and then there's always achievements to be gotten. There's also a substantial amount of levels in the DLC packs, which if you enjoy the game might be worth downloading.
All in all, Defense Grid is a generic but addictive, cheap but fun tower defense game, that for the very good price of absolutely nothing, is a bargain. Even now, for 400 Microsoft Points, it is worth picking up and trying. It doesn't do anything outside the box, but what it does it does well.
Gameplay: 89%
Graphics: 88%
Lifespan: 64%
Innovation: 40%
Accessibility: 70%
Overall: 80%
Thanks for reading.