Portal 2 courses during Cooperative Testing Initiative

Course Six: Art Therapy
Set after the conclusion of the Mobility Gels course, GLaDOS has reassembled the bots for testing again and claims that it has been 100,000 years since they were last reassembled.

Interestingly, the sixth course was initially going to consist of advanced test chambers during Portal 2 ' s development, months before the game was released. However, this was scrapped and was removed from the final game. The Peer Review DLC to Portal 2 instead adds only challenge modes to single-player and co-op, with no sign of advanced test chambers. The Art Therapy course is referred to as an additional course instead of the "sixth course".

Non-Emotional Manipulation
All owners of the Portal 2 Sixense MotionPack DLC receive this course for free. It makes use of the new Portal Surfing and One-to-One mechanics.