Unstoppable Gorg is a tower defense game set in space. As our curiosity continues to seek knowledge beyond the brinks of the solar system, we discover that we are not alone in the universe. Near the orbit of Neptune, Planet X shelters an advanced civilization known as the Gorg. But this event comes with an unpleasant surprise. The inhabitants unleash a vast armada of alien flying saucers against our nearby Space Base Zulu. Soon, the entire humanity faces an unprecedented danger. You take control of Captain Adam, Earth's ambassador, now tasked with destroying the alien menace before it annihilates all signs of human life. The overall style and the cutscenes are a throwback to 1950s alien invasion movies, such as Plan 9 From Outer Space, Target Earth, War of the Worlds and so on.
There are three modes to try out: Story, Challenges and Arcade. In the Story mode you progress through 21 successive chapters tied together by a story. The Challenges mode represents 21 alternate versions of the original levels, spiced up with additional hurdles and increased difficulty. In Arcade, you need to survive as long as you can against an endless swarm of alien enemies. Both, the Challenges and the Arcade levels are unlocked by completing the original chapters in the Story mode, as well as completing different tasks, like generating a fixed amount of research points or money, losing no satellites, etc.
The gameplay consists of defending your base against waves of alien ships that come at you along predetermined paths. At the start of the game you select from a variety of satellites, which you can place on the slots populating several orbits around your base. There are different types of satellites: solar generator, resource generator, cannons, lasers, atomic bombs, satellites that slow down enemies etc. To place a satellite you need to have enough money made by the solar generator. A combat satellite, for example one of your missile launchers, will attack an enemy vessel once it is close enough. Eventually, using other satellites, you'll be able to increase the range of your combat satellites or employ other tricks in order to attack more efficiently. The orbits themselves can be rotated, so as to adapt to other emerging enemy paths. Later in the game, you'll face two additional alien races: the robotic Sunbots and the Brain Riders. Each race has a weakness against particular types of weapons - part of the challenge is finding out which.