Simplify the following text for a Grade 4 native English-speaking person.
Original: The player 's mission is to infiltrate Naju , a large planet-like object which aliens sent hurtling towards the Earth . While inside , the player must activate ten safety devices in order to initialize Naju 's self-destruct mechanism and destroy the alien world before it reaches Earth .
Simplified: The player is to destroy the alien moon Naju before it gets to Earth .