Recently, your band of adventurers took on a sketchy merchant who claimed to have a map and password to the Lost Laboratory of Alfonso the Absentminded, an enchanter of great talent and greater forgetfulness. While he didn't seem entirely trustworthy, you decided the reward was worth the risk, and traveled through treacherous terrain for a week before eventually reaching the sealed door to the laboratory.

On a pedestal beside the door is an 8 by 8 grid of tiny wells, and a smooth, raised stone rectangle at the edge of the pedestal that appears to activate some mechanism. There is also a firefly hovering above each well, and your party's wizard explains that these are flipflopperflies, a magical breed of firefly that will alternate between being lit or dimmed when they eat enchanted nectar. She surmises that getting the proper combination of fireflies to light up will open the door, and produces a single bottle of this nectar, which contains exactly 64 drops.

There is a small square of bright yellow parchment attached to the pedestal, apparently enchanted to never fall off, with the message "When ASKed for a KEY, enter PASSWORD".

It's late, so you decide to rest for the night before attempting to get into the lab. Around dawn, at the end of the merchant's watch, the party is awoken by a loud "WOOMPH" from the pedestal. Rushing over you find that some of the fireflies are now glowing, and the bottle of nectar is about half empty!

The merchants clothes are all on the ground in front of the pedestal, and a large salamander crawls out one of the sleeves. It appears that the merchant attempted to enter the password and loot the lab on his own, but the flipflopperflies didn't behave as he expected, and he triggered some sort of trap.

The salamander stares at you forlornly for a moment, then sketches something in the dirt before scampering off towards the warm stones around the campfire, content to nap there. The sketch is of 5 dots forming a cross, with arrows pointing in and out from the center dot to each of the surrounding dots.

Here is the current state of the pedestal:

A stone pedestal with an 8 by 8 grid of wells and fireflies. There is a sticky note on the corner of the pedestal, and a diagram in the dirt beneath it. There is no extra information in the image, it's just here for thematic purposes.

Here is the state of the fireflies as plain text, where 0 means dimmed and 1 means lit:


Can you determine the password? Do you have enough nectar left to open the door?


1 Answer 1


The merchant appears to have had the idea

to read "ASK KEY PASSWORD" as "ASCII PASSWORD", and enter in the binary representation of the word PASSWORD row-by-row.


he failed to realize that the flipflopperflies change their state not only upon getting a drop of nectar, they also change their state when their neighbors get a drop of nectar! This means they work according to Lights Out rules.

Reversing the merchant's steps, we see that they're not quite what one would expect given this, though. The cells that are different are:


This means the merchant knew something that's not obvious from the note - the actual password is PAS5WORD.

So, the merchant entered this pattern, using 30 drops:

Our goal is to have this pattern be the end result, rather than blindly entering drops in those positions. To get there from the current configuration, we can use 30 drops like this:
drops to enter
And we'll open the door with 4 drops to spare!

  • $\begingroup$ The merchant knew the password ahead of time and entered the drops correctly for what it is. Otherwise, you've pretty much got it! $\endgroup$
    – DqwertyC
    Commented Jun 12 at 19:25
  • $\begingroup$ @DqwertyC Ah, I see - how's this? $\endgroup$
    – Deusovi
    Commented Jun 13 at 12:43

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