Alien Tower Defense

The aliens are invading this wonderful forest and you are the only one that can come up with some strategies that will keep them at bay. You will have to place many turrets in this tower defense game and you must place them well or the aliens will pass right through them. The base must be kept alive at all cost. To place turrets you need to spend some resources and with each new level you get a base amount of them, but after that you will have to earn them with each kill. Each turret has its strength and weaknesses so make sure you build the right types or else it will take longer to kill certain aliens.