Backscratcher explores the relationship between test subject and Frankencube in a test chamber consisting of several small puzzles where the two work together to solve puzzles.
Backscratcher came out of the unique concept of the Frankencube object from Portal 2. The level is intended to be an exploration into the potential puzzles and mechanics that Frankencubes can inspire. The core concept of the puzzle's dynamics and name come from expression of "I scratch your back, you scratch mine."
The Frankencube object is only used in Portal 2 as a unique skin for a cube, and for that reason using the behavior of it moving around on its legs is completely new and unexplored. The biggest challenge for this level was using a behavior that exists in the game but has no puzzles made for it, which essentially meant creating things from scratch. I had to explore the metrics of Frankencube movement in order to design puzzles for it.
Using the adage of "help others and they will help you" gave me a clear idea for how I wanted puzzles in Backscratcher to work. For every one puzzle in which players use Frankencubes to get past an obstacle, there is one puzzle where the Frankencube needs the player's help to be escorted past it as well.
Because these puzzles were totally new ideas from the base Portal 2 game I split the level in halves to teach Frankencube metrics. The first half shows how you escort Frankencube, then how he helps you past an obstacle, then how you together can overcome turrets. After dropping into the lower area these same types of puzzles exist but open up to the player to do in whatever order they choose.
The test chamber begins with a lone Frankencube, fizzler, and red laser. The player can clearly see their first few puzzles from here.
The first puzzle requires the player to help the Frankencube. By the player standing on the button Frankencube can hop across and past the fizzler on his ow without fizzling.
Contrasting the first puzzle, the player cannot cross the red lasers but Frankencube can. Having him help you by being thrown past the beams will lower them for the player. A boost pad is nearby to prevent the player from throwing Frankencube out of reach.
Finally in the first half of the test, the player and Frankencube approach a Turret, and the player learns to defend using Frankencube.
The second area is made up of 3 puzzles that can be done in any order. The first puzzle is reminiscent of the first puzzle from part 1, having the player lower the fizzler for Frankencube to walk onto the boost pad and defeat the turret, letting the player safely leave the test.
The second puzzle uses what was learned from the second puzzle of area 1, letting Frankencube drop down past the red lasers instead of the player. The player stands on the button and these wall panels open to let Frankencube walk himself into a portal and past the lasers.
The final puzzle requires Frankencube to stand on the button for the player. While Frankencube is on the button the player can use the portals to access the final button which raises the last staircase to exit the test chamber.