Complex sentence: Zack Lightman glances out his classroom window and spots a UFO that resembles a ship from a video game that he plays every night, a hugely popular online air combat simulator called "Armada", in which gamers protect Earth from alien invaders.
Split into simpler sentences: Zack Lightman glances out his classroom window and spots a UFO. The ship he's staring at is straight out of the video game he plays every night, a hugely popular online air combat simulator called "Armada", in which gamers protect Earth from alien invaders.