"You're General Voltrex in charge of wave #27 for the earth invasion. Heroes will rush for your position and try to get through your defenses. Enlist new monsters and develop technologies to make wave #27 the ultimate squadron!"
This game will look very familiar on startup (specifically, like Galaga) but it is a very, very different beast. Use your mouse to control the attacking aliens, controlling when they fire and swoop, doing your best to preserve your ships while raining down bombs at the "player" below. It's a trip.