Mission 80

There is a shield generator on the bottom left side of the level. It is best if you can avoid destroying it since it stops you from falling into the violet area, which will damage you. Fighting the Overlord on the shield is ideal since it can't use its charge attack on you - it will fall through the shield.

The white area prevents you from making or using portals while you are in it, but you can use a portal to enter the area. Also, your jetpack fuel is drained while you are inside it. Extended stays in the area must rely on primitive technologies like the Climbing Unit. There is a disabling bomber at the top which you should kill to make your fight with the Overlord easier.

Destroy as many of the platforms in the white area as possible. The Overlord can make many traps out of them.