In the game, you need to destroy hordes of aliens, periodically completing simple additional missions like searching for explosives, setting mines and restoring electricity supply. There are also RPG elements: you need to buy new weapons and equipment for in-game currency, as well as upgrade your character.
Usually the game for Android costs 439 rubles, but now it can be picked up for free. It is unknown how long the promotion will last, so it makes sense to hurry up.