Asteroid Tower Defense is a great game from Deonn Games. It mixes up the conventional tower defense mechanics and comes up with something fairly unique and a lot of fun. This is definitely a game any tower defense fan should try out.
Rather than put you on a field or a closed circuit to place your towers like in other tower defense games, you build your defense from the bottom of the screen and out. You start out with one little command post in space, and you can only build new towers as attachments to one of the four sides. This is the only way to build anything in the game. Asteroids hurtle towards Earth and it's your job to defend it.
Every time you start a new game, you will go through the games simple tutorial again, which just means that certain messages will pop up at certain times. You're still free to do what you want for the most part. You have four guns to choose from. Quick-firing lasers, homing missiles, a freeze ray thing, and a splitter, which I just thought of as a sniper. As you expand your base, you will expend more and more energy.
You'll have to remember to build plenty of solar panels to keep your guns from shutting down. You can also build maintenance droids that fix any towers within reach, and protective shield structures, which you will be building plenty of. Just about every structure can be upgraded to a more powerful form. There is a lot to the heads up display and the different asteroids, and the game doesn't really teach you about them. Luckily, there is a page that explains these elements that you can reference should you forget anything.
At first the game is a lot of fun, as you expand your base and balance your upgrading. Eventually, you'll complete your great big death station, and the game focus becomes fortification--building multi-layered defense walls and maintaining them as they get destroyed. This is where the game gets boring for a good long while. I got tired of just building more and more shields, it wasn't a lot of fun to me. It eventually gets hectic though, with some really strong and fast moving asteroids blindsiding you and obliterating your defenses. I actually found it really amusing to just watch my massive base get steamrolled by a few massive flaming meteors. The whole point of the game is just to survive as long as you can and place in the leader boards. With only the one game mode, there isn't a whole lot to this app.
All in all, this is a pretty solid tower defense game. The visuals and sound effects are good, and the game play dares to try something new. This is a free app, so you're going to be dealing with advertisements. You're bound to click on a few due to the way they're placed, but it won't be much of a problem. Definitely check this one out.