# On The Subject of ​?​?​?

(This is the last of a series of puzzles written for Timwi for a Secret Santa puzzle exchange, themed around various custom modules for the game Keep Talking and Nobody Explodes. Note: Unlike previous puzzles in this series, KTaNE knowledge is necessary to solve this puzzle; the necessary knowledge can be found on Timwi's site.)

# On The Subject of ???

To solve this last puzzle, I have a suggestion:
Just add these few glyphs to the guide page in question.
Take new digit tetrads, use each on the next
to resolve the conundrum you see in this text:

The principles, truths that have been recompiled
that Timwi has indexed and sorted and filed
for these all as one, what might be an apt name?

This is a metapuzzle using the puzzles linked in the above table

For convenience's sake, here are the answers to the above puzzles:

MATTRESS, RHOMBUS, EYEBRIGHT, IBEX
SOCIETY, REGISTERED OWNER, BANANA, STARTER
CHINESE LANTERN, LOGGED, ETHOS, EUPHORIA
ELEFTHERIA I THANATOS, SHOVEL, ANDROID, YEAR

Hint:

Each of the previous puzzles was themed after a single module Timwi has made. This one is as well; it will be immediately clear which one is the right one when you find it.

• This might be a module of rot13(Xhqbfhqbxhf), but this is just a guess. – athin Feb 19 '20 at 3:42
• Yeah, that's very likely. I can whip up an answer with partial progress in a few moments. – mbingo Feb 19 '20 at 3:44

First, notice that...

... the sixteen feeder puzzles each relate to a module created by Timwi. This puzzle does too—we just need to determine which.

The instructions are in verse, which leads us to Kudosudokus, which has instructions written in the same manner.

Accordingly...

... we need to take the answers in the grid and assign them numbers, using some of the categories described in the module's instructions.

Colors are described by four of the answers: CHINESE LANTERN (red), BANANA (yellow), ANDROID (green), IBEX (brown).

Directions are contained within four of the answer strings: REGISTERE(DOWN)ER, E(LEFT)HERIA I THANATOS, E(UP)HORIA, EYEB(RIGHT).

Elements can be prepended to four of the answers to make a common phrase: FIRESTARTER, WATERLOGGED, EARTH YEAR, AIR MATTRESS.

Suits are synonyms for four of the answers: SHOVEL (spade), ETHOS (heart), SOCIETY (club), RHOMBUS (diamond).

The above are ordered as described in the module's instructions (i.e. the first listed in each category corresponds to 1, the second to 2, etc.).

This yields...

... the following grid (with letters representing the associated category as named above).

E4 S4 D4 C4
S3 D1 C2 E1
C1 E2 S2 D3
D2 S1 C3 E3
Sadly, this is not a valid Sudoku grid. This is unacceptable.

To fix that...

... we make four Sudoku grids!

Recall that we were told to "take new digit tetrads". This is telling us to take the four digits from each category and solve Sudoku grids using those as starting points.

For example, the color tetrad forms this starting grid:

_ _ _ 4
_ _ 2 _
1 _ _ _
_ _ 3 _
This is a solvable Sudoku with the following solution:

3 2 1 4
4 1 2 3
1 3 4 2
2 4 3 1
The other solutions are as follows:

Directions

3 2 4 1
4 1 3 2
1 4 2 3
2 3 1 4
Elements

4 1 3 2
2 3 4 1
3 2 1 4
1 4 2 3
Suits

1 4 3 2
3 2 1 4
4 3 2 1
2 1 4 3

Finally...

... we come to the glyphs at the top. Note that each image corresponds to one of the categories.

Top left: paintbrush (colors)
Top right: some symbol related to the elements
Bottom right: arrow keys (directions)
Bottom left: playing cards (suits)

This cycle tells us which solved Sudoku grid to use for indexing into each answer in the answer grid.

For example, the top left cell in the answer grid is MATTRESS, which is in the elements category (AIR MATTRESS). The glyph cycle tells us that we use the solved color Sudoku grid to index into element cells. The color grid has a 3 in that position, so we extract the third character in MATTRESS, which is T.

Proceeding in this manner reveals an apt name for these compiled principles that help us defuse bombs:

THE BIG BANG THEORY

I think this is a masterful meta—thank you, Deusovi, for writing these great puzzles and sending them our way!

Also, credit to HTM and Omega Krypton—thank you for joining me in co-solving!

• I think it's great :)))))))) – Prince North Læraðr Feb 19 '20 at 5:45
• That's completely correct! Nicely done, hope you enjoyed the puzzle! (The second symbol is this, in case you're curious.) – Deusovi Feb 20 '20 at 15:42