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Tower defense games are all over the place in the Android Market but naturally only a few can claim they are actually worth playing. HexDefense is one of those games that stands out among the rest. The game takes place in a futuristic-type setting where all the objects glow. Each tower can be placed in a hexagon and it is a required gameplay mechanic that you direct the flow of traffic. The graphics in the game are pretty awesome and the game even offered to change the brightness of my phone for me to improve the experience.
The game comes with 15 different levels which was plenty considering even the first level is a challenge to pass. With four different towers to place and upgrade, you really need to be selective with your strategy.
I enjoyed this game a ton and definitely would recommend checking it out. There is a free version to try just in case your older phone may not be able to handle it.