The gameplay of Portal 2 is based on its predecessor Portal, where the player, with the use of portals, solves puzzles.
New gameplay elements such as Mobility Gels, the Aerial Faith Plate and the Thermal Discouragement Beam were implemented as means for the player to master in order to solve puzzles.
Cooperative play is a new game mode introduced to Portal 2. The campaign features two characters, ATLAS and P-body. The two players must work together to pass tests and areas outside the test chambers. The developers implemented robotic characters in order to ease explanation of a respawning system, giving the story explanation that humans could not be trusted.
The soundtrack is split into 3 volumes, with a total of 64 songs. The theme of the music is pretty upbeat, largely electronic, with a few quieter ambient tracks, but also a few very busy techno pieces.
You can download the Soundtrack on the official Portal website thinkwithportals.com.