GRID

The game consists of a number of missions, each of which is to be completed in succession by defending the power cores from the aliens. As the game progresses, the aliens become more powerful and more numerous. You will need to use different types of towers, each with its own strengths and weaknesses, to protect yourself.

There are several types of towers, each with its own strengths and weaknesses, and each of which can be upgraded to increase its effectiveness. Placing and upgrading towers costs resources, which can be gained by destroying the aliens, or from interest on your current stock of resources. You will also acquire an orbital laser that can be fired to destroy the aliens at a distance.

Completing missions successfully will earn you medals (bronze, silver, or gold) based on the number of cores remaining and points acquired. Completing missions unlocks later missions as well as alternate play modes for the mission completed, such as a challenge mode with more powerful aliens or a mode in which only a limited number of towers can be placed.