Part 17: Aerial Havoc Don't start here! Play the original version first! Since you, Marquis Andrews, saved Aperture's test chambers from being tested by test subjects from Dark Cave's universe, several test chambers became much harder, such as one of Charl...

Part 18: Close Encounters Of The Deadly Kind Don't start here! Play the original one first! Difficulty: Hard Hazards: Goo, Laser Estimated Time: ? Twists: In the first room you HAVE to open the platform to the other room via a button, and there's less spac...

Part 19: 06 Was Vitrified Don't start here! Play the original one first! The hardest test chamber of the testing track has been re-designed by one of Aperture's biggest threats. Neither Cave Johnson or GLaDOS noticed that. Just a warning to you, your testi...

Part 28: Change Flight Directions (Advanced) Difficulty: Super Hard Hazards: Turrets, Laser Fields Estimated Time: ? Twists: The polarity timer for the funnel in Room 1 is shorter, there's only 1 ramp in the second room, and there is an extra room before t...

Battlefield (Advanced) Don't start here! Play the original version first! This is not an official extra map. The most turret-involved test chamber I've ever built has an advanced version as of now. Difficulty: Super Hard Estimated Time: ? Hazards: Turrets,...