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 starting area of the test chamber, which is designed to be linear to demonstrate the types of ways to interact with the Frankencube.
The second area of the test chamber, where the player is given 3 puzzles that build on the skills from the first area.
Another view of the second area from the opposite corner.
The first puzzle starts with a fizzler. The player can get across this but Frankencube cannot. The player must place the Frankencube in a position where it can jump on its own past the fizzler while the player holds it open.
The next puzzle is a reverse of the first; while Frankencube can go through the laser field, the player cannot. The player drops Frankencube onto the boost pad to lower the laser field for the player to cross.
The final puzzle of the third area is simply a demonstration of how to use the Frankencube to block turret fire and destroy turrets.
A turret blocks the exit in the second area, and both a fizzler and a laser block the path to it. Escorting the Frankencube past the fizzler like in the earlier puzzle will knock the turret down safely.
In the corner of the room is a single button that opens one of the staircases. Frankencube must sit on the button to allow the player to portal up to this button to open half of the exit path.
The final part of the puzzle involved dropping Frankencube from a portal above a laser. The player must step on a button and guide Frankencube through a portal that drops it onto a second button, opening the final half of the exit.