FreeGamia Plasm Defence II - free download

In the near future, Earth is finally at peace. The war has ended, and division of resources is now equal for all remaining countries. With the growth of technology, the ability to reach escape velocity has allowed several spacecraft to be sent out of the solar system. Soon after contact with these ships had been lost, and people are waiting to hear from them or have at least one return. And wait they did... Ten years go by and now an armada of spacecraft is approaching Earth, and they do not look manmade. Attempts to contact the crews of these ships are in vain, and the people, with their aggressive tendencies still intact, decided to attack the unknown ships ostensibly to protect the planet, but these attacks had no impact. The unknown ships were too strong. But this attack has provoked the aliens who decide to take over the Earth and all its resources after first clearing the planet of people. The aliens have landed ground combat forces, vaguely reminiscent of human tanks, mixed with futuristic spaceships. you have to fight them, using all the modern advances of technology!

The game is made in the genre of Tower Defense whereby you build turrets, improve them, use the additional features and generally doing everything you can to destroy enemy units.