Celestial Defense is a decent tower defense from GameCell. It definitely has flaws, from the very slow and arduous levels to smaller, technical issues like intermittent freezing, but it is fairly well designed and is great for a challenge. This game can be very brutal, and often requires you to think outside of the box.
Your goal is to defend various power generators from vicious aliens. Levels take place on winding paths made up of hexagonal tiles. Towers can only be placed on specified tiles, so you'll have to use your spaces wisely. You'll be placing different kinds of weapons with unique ammunition, including laser, electric, plasma, sonic, and flame. You'll also have to place power generators in order to gather enough resources to build towers at all. The wrinkle is that enemies will stop and destroy your power generators, which you'll have to use to your advantage if you want to do well. As you win and gain resources, you can buy better towers in the armory.
The game does seem rather amateur in its design. It could have been better with some quicker levels or different difficulty settings, perhaps. One example of the bad design is in the early levels, where an enemy can get to the generator and be out of range of every surrounding weapon. Some levels may seem impossible, but attempting wildly different strategies can get you surprising results. Building almost nothing but generators at the start of a level knowing they'll mostly be destroyed just so you can build and upgrade weapons faster is one to keep in mind. There is a helpful almanac with all enemies and towers detailed inside.
The visuals are simple and 3-D, which is uncommon for a tower defense. There's nothing special about them, but they're inoffensive. The electronic music is pretty good too. OpenFeint achievements and leaderboards are supported as well. This game will be loved by some, and absolutely hated by others. I enjoyed it, but if you don't want a brutal, slow, and methodical tower defense, you'd best move along. otherwise, Celestial Defense can be yours for one dollar at the time of this review. Before you make any decisions, there is a lite version to try as well.