Not Enough Firepower? Take a General's Hand and Rub It Together

When the arrogant fleets of advanced alien civilizations arrived in the solar system and prepared to harvest this backward planet, what greeted them were Dyson spheres rising from the ground, overwhelming two-way foils, and a group of two-dimensional ship girls who looked cute but actually exploded stars directly with one flat-A shot... "Where are the lower carbon-based creatures that were promised? What's going on with these dimensionality reduction weapons flying all over the sky?!