The Earth has been invaded!
An alien civilization has built a network of Portals in the planetary system of Neptune that allows entry to the Earth by creating black holes in the atmosphere of our planet. You have been sent to the main satellite of Neptune: Triton. Your mission there will be to protect the Interplanetary Portal and prevent the invasion of new alien troops as well as destroy the network of Portals of the rest of Neptune's satellites. You must defend and build a fortification around the Portal to prevent access. You must obtain energy to be able to use the Triton Portal and travel to the Neptune satellites to end this threat and destroy all the Portals, strongly protected by the invaders.