"In the former half of each trial, you are granted the opportunity to study the pattern of obstacles. The latter half then plunges you into darkness." -Gentleman, 'Grand Opening'
The Memory Evaluation is a side tunnel that branches off of the Low-Power Tunnel, part 4. It appears once you finish the Bridge Building and the Angel Missions. The tunnel consists of seven levels, all of which can only be played with the Gentleman. All the levels were designed by Karsh777, however, canonically, all credit is given to the Gentleman. He designed the Memory Evaluation by using a detached ring to move the tiles of the tunnels into specific patterns. The tunnel was implemented into the game on September 27, 2016.
Each level of the Memory Evaluation begins with a kind of gate, signalizing that the trial is beginning. The gates are each three tiles long and circle the width of the tunnel, and there is one unlit tile in the center of each side of the gate. After the initial gate, there is a series of platforms arranged in a specific pattern, then another identical gate. Following the second gate there is another set of platforms in the same pattern, however, they are mostly or all unlit, requiring the player to somewhat memorize the pattern from before. Some of the patterns are flipped making it harder to memorize.
NOTE: Turning up the screen brightness completely of your monitor or device may make finishing the Memory Evaluation significantly easier, and is in no way considered cheating.
The following is a brief description of the story in the Memory Evaluation. More information on the story can be found here.
In the cutscene 'Standards to Uphold', the Gentleman reveals that he does actually want to go home, but not until his "project" is ready. His project actually is the Memory Evaluation, and he works on it while the Runner's group is trying to reach the Wormhole, and Angel's group is heading back to the Planet. He finishes the Memory Evaluation at some time between the cutscenes 'Of Course' and 'Obvious'. After it is finished, he practices his opening speech for the grand opening of the Memory Evaluation several times with the Lizard, as shown in the cutscene 'Grand Opening'. Based on his practice speech, it seems that the Gentleman means for the Memory Evaluation be some sort of attraction if and/or when other aliens from the Planet come into the Tunnels.