Over the Cloud: Lost Planet

The mankind found an unknown ore in a comet that crashed on Earth…
Because of this, they accomplished to develop an extraordinary civilization. The speed of scientific development increased rapidly and faced a new civilized age. Old age spaceships became artifacts and were valued enough to consider them as historical pieces.
These new spaceships went deep into the space to collect even more ores. They named this ore, Oort-nite. However, one day, monsters appeared across the world and attacked mankind simultaneously.