: This was the first major free DLC for Portal 2, adding a new co-op track and challenge modes for both single and multiplayer.
The most notable "interesting paper" regarding the game is titled published in the journal Computers & Education . Portal 2 Free Download (v2022.11.19)
While the "v2022.11.19" version likely refers to a specific unofficial update or repack, there are official ways to get free Portal 2 content and academic-style analyses: : This was the first major free DLC