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Solutions for Act IV Scene 2 - On The Subject Of Memory

The title and the layout of each set of displays reference the local multiplayer game Keep Talking and Nobody Explodes, in which one player has access to a virtual "bomb" and must be guided by a second player, the "expert", who has access to a bomb defusal manual. In case the title was not enough to go by, an additional clue can be found by reading the highlighted buttons of each set as ternary (e.g. 112 = 1x9 + 1x3 + 2x1 = 14 = N), giving the message "NOBODYEXPLODES".

Researching the game should lead to bombmanual.com, which is the site containing the manual used by the "expert" player. As of writing, the puzzle's title can be found within the manual as a section heading, hinting that this is the part of the manual we need.

Reading the instructions on disarming the game's memory modules should lead to the realisation that we are in the reverse situation - we know which buttons were pressed for each set of displays, but we don't know the rules which dictate when to press which button. However, if we assume that the possible instruction types match that of the manual, we can work out most of the rules.

The possible instruction types are:

  • Press the button at position X
  • Press the button with label X
  • Press the button at the same position as stage Y
  • Press the button with the same label as stage Y

Using this, the rules used in the puzzle can be worked out to be:

  • Stage 1
    • A: Press the button in the third position
    • B: Press the button in the first position
    • C: Press the button with label 2
  • Stage 2
    • A: Press the button in the same position as stage 1
    • B: Press the button with the same label as stage 1
    • C: Press the button with label 1
  • Stage 3
    • A: Press the button in the same position as stage 2
    • B: Press the button with the same label as stage 2 OR press the button with label 1
    • C: Press the button in the same position as stage 1

Note that there is an ambiguity with B in stage 3, but this turns out to be irrelevant.

The next obvious step is to apply these instructions to the final 3 sets of displays. However, each set of displays has a stage missing! The leap is then to realise that we need to try all three possible displays for that stage.

Doing this gives

121, 012, 200
100, 110, 110
012, 201, 201

which can be decoded from ternary to give perilless, which is what it's like if nobody explodes.


Design notes:

The ambiguity with B in stage 3 arises from the fact that the only letter in "NOBODYEXPLODES" which has the same two final ternary digits is D.

Initially the puzzle was much more ambitious, with the idea being one final set of displays where none of the stages had their ABCs shown. The leap was similar, with the intent being to try all 27 possible combinations in order to extract a message. However, it became apparent that this was nigh on impossible, since all combinations starting with A had to have the same first ternary digit, and ditto for B/C. Furthermore, all combinations starting with AA had to have the same first two ternary digits, and ditto with AB, AC, BA and so forth. Another idea was to use only permutations of ABC in the final displays, forming a 6-letter answer, but a good answer word with a nice, varied instruction set was hard to find.

The answer is: perilless