How It Works
- First, the first chunk of the product code is straightforward alphabetic indexing. It says "index into supply name by amount" (next two columns on spreadsheet)
- If they count the number of each supply and index into the supply name, you get the next two columns. Notice that this looks like nonsense. (next two columns!)
- The last chunk of the product code contains zeroes to pad them to the same length, and then a number (1-26). Reordering the index letters by this ordering, you get "find nato letters" and then a bunch of garbage (the garbage is in alpha order though. It says CCEEHKPSSUW.) (columns 7-8)
- NATO letters in the Supply Name can be found by applying the mask which is the middle chunk of the product code (note, there are indeed 26 supplies!)
- The masks are a series of 0s and 1s.
- The mask is the same length as the supply name
- Taking the letters from the supply name that are 1s in the mask yields a three or four character string. For instance, WOOLFAT / 0011100 = OLF.
- The 3 or 4 letters you get uniquely matches one of the NATO letters (in this case gOLF)
- You can see this in columns 9-11
If you reorder all the index letters originally obtained from each Supply Name by the NATO letter associated with their supply name instead of the given order from the product ID, they now say THEANSWERSDEFUNCTSTOCKPILE
Some of the inspiration for this puzzle was a puzzle in the 2009 Zoobotics Game that I played as an intern. NATO Puppets introduced me to concept of camouflaging NATO letters inside other words or phrases. The "ah-ha" moment when I understood the puzzle mechanism stuck with me, and I wanted to do something similar eventually.
You may have noticed that some of the "supplies" were perhaps not standard items found in a fallout shelter. It turns out that there were actually some pretty harsh constraints necessary to cram in all the data I wanted for this puzzle. It was a lot easier the first time I wrote this puzzle, when I utterly ignored the NATO letters I had chosen for the final solve. It wasn't until someone tested the puzzle for me that I realized that I'd left out a step. Protip: When you decide to write a puzzle about NATO letters, it helps to actually use NATO letters.
Another Protip: the cheapest kind of cans we coudl find on relatively short notice were generic brand salted and unsalted tomato sauce. Redmond QFC is also 15 cents cheaper than Bellevue QFC. 35 cents versus 40 cents for cat food.