Quick Response

Written by Olga Vinogradova and Justin Yokota

Answer: HEARTH

In Act II, some puzzles are entangled with one in the opposite dimension. The two puzzles each have their own theme, core mechanic, answer, and solution, but each requires some information or action from the other in order to solve. This puzzle is entangled with Single Elimination.

The puzzle presents a 26x26 grayscale image. The flavortext suggests taking a look at the least significant bitmask; this is made easier by the pgm format provided, which gives (in plaintext) the 0-255 gray values of each pixel. This yields the following image:

The cluephrase here is APPLY TITLE MASKS ON OTHER 7, but there’s a 5-bit corruption where the bits are inverted from what they should be, highlighted in red in the image above. As it turns out, "Quick Response" is the acronym "QR" used in "QR codes". When creating a QR code, there are 8 masks which are XORed into the main space; for any given QR code, one is chosen to minimize the number of consecutive white or black cells (this helps with scan accuracy). The 8 masks are available on Wikipedia and have a canonical ordering. The rest of the puzzle consists of taking the other 7 bits of the image and applying the appropriate mask to them. After applying the correct mask, each image forms a subpuzzle, again with a 5-bit corruption. To aid in solving the subpuzzles, the answers are in alphabetical order by their bitmask layer.

The solution to each bitmask subpuzzle is presented below. The masked image is presented on the left, the QR mask used in the center, and the unmasked image on the right. The corrupted 5 bits are marked in red.

Bitmask Layer 7

The image, after applying QR Mask 3, is that of the constellation ANDROMEDA. The corruption is the line of 5 filled bits.

Bitmask Layer 6

The image, after applying QR Mask 5, is the following. The upper-left corner has the letters "BF", which is a reference to the programming language "Brainf*ck". In Brainf*ck, there are only 8 characters which are used: +-<>.,[]. These characters are on the sides, along with a string of 3 bits directly underneath. This is an indicator of how each Brainf*ck character is encoded in 3 bits. (The comma character has no given encoding, because it does not occur in our program: it is used in Brainf*ck to take input.) The center 26x18 block can thus be translated to a BF program, read from left-to-right top-to-bottom which yields the answer ASSEMBLY when run. The corruption can easily be found on the right side, as it affects the right bracket.

Bitmask Layer 5

The image, after applying QR Mask 0, yields Morse code. Decoding the Morse code yields the clue "Blind bird endlessly left rice with greed 7". Treating this as a cryptic clue yields the answer AVARICE (AVIAN - I - N = AVA to the left of RICE). The corruption is in the center of the image.

Bitmask Layer 4

The image, after applying QR Mask 2, yields a QR code. Scanning it yields Subpart answer CONGRATULATIONS. The corruption can be found by noting that the upper-right square has been corrupted slightly. Directly beneath the square is a line of metadata which is also copied to the right of the upper-left square; the difference between the two disambiguates the corruption completely.

Bitmask Layer 3

The image, after applying QR Mask 4, yields a maze. The maze traces out a DELTA. The corruption is the 5 white bits isolated from the rest of the maze.

Bitmask Layer 2

The image, after applying QR Mask 7, yields the Japanese clue 九州最北県 that roughly translate to "Kyushu northernmost prefecture". The answer is the northernmost prefecture of Japan’s Kyushu island, which is FUKUOKA. The corruption can be found in the center, extending the second-to-last stroke of 最.

Bitmask Layer 1

The image, after applying QR Mask 1, yields some polyominoes. All of these are examples of a pattern in Conway's Game of Life called the METHUSELAH. The exception is the line of 5 in the upper right; this forms the corruption.

At this point, we use the entangled puzzle Single Elimination to extract 2 letters from each bitmask layer answer, ordering by QR mask used. In Single Elimination, when we enter an answer, we typically obtain two letters as the winners of the two single eliminination brackets. However, if we input a bitmask layer answer into Single Elimination, we obtain the phrase "Error: Unknown Interference". This suggests that we need to compute the winner of the brackets ourselves. The extracted letters are summarized in the following table:

QR Mask NumberWordLeftbye LetterRightbye Letter

Reading the extracted letters, we obtain the cluephrase VESTA GODDESS OF and hence obtain the answer HEARTH.

Author's Notes

The origin of this puzzle was from Puzzle Potluck 3, where the final runaround involved receiving a QR code piece-by-piece. Our team got stuck on one of the pieces and thus couldn't continue for several hours. We later learned that some team members had manually decoded the QR code, thus getting the next step with fewer pieces. As such, I learned how to decode QR codes manually, and set about making a puzzle related to that.

The steganography idea was originally from a puzzle idea for Teammate Hunt 2020; in that version, there would have been 24 sub puzzles, culminating in 3 minimetas (one for R, one for G, one for B) and a final minimetameta. This eventually got cut due to being basically a full hunt in one puzzle. In making this puzzle, we decided on answers before making the Single Elimination grid. It took a few tries for our program to spit out a working solution, but overall, I was very satisfied with how this puzzle turned out.