In Angry Birds Space for the iPhone, iPad, and Android platforms, there are six hidden levels in the Eggsteroids world.
Unlocking these special levels requires you to find the hidden golden eggs scattered throughout the game. Some of them are fairly obvious, but some of them are hidden fairly well.
Check out my full Angry Birds Space: Golden Egg Locations guide if you want to know exactly how to find them. This guide has screenshots of all of the hidden golden egg locations.
