This puzzle is just what it says on the tin: A Minesweeper
game following Quantum Mechanical rules. The basics can be picked up
from randomly clicking around. The “quantum state” of the
15x15 board is a uniform superposition of many possible
“classical states”, each consisting of 100 mines placed
around the board. In the classical version clicking on a square with a
mine would kill you, but in the quantum version, it simply restricts
the superposition to only those states with no mine on that
square. The exception is if **all** remaining states have a mine on
that square, in which case you die. In all possible
Universes. Ouch.

The numbers in clicked squares work similarly to the classical
version, but instead of counting the number of adjacent mines,
they count the **average** number of adjacent
mines across all remaining states. Thus, they tend to not be
integers. Also, clicking somewhere on the board tends to
decrease the immediately adjacent numbers (since you've
removed any possibility of a mine in that square), but
increase the numbers everywhere else, since the remaining
mines are now distributed among fewer possible squares. In
practice, this mostly means you can click around freely until
the last 100 squares, at which point they are guaranteed to
kill you. And indeed if the starting superposition consisted
of every possible configuration, this is how it would work.

But you may notice that this isn't **quite**
true; there are a few irregularities. Indeed, from
experimentation you might discover that clicking on certain
squares on the board will strongly affect other, distant,
squares (much more than the small increase you'd
expect). Ah, this is another quantum mechanical feature: some
squares are “entangled” with each other! The first
step is to identify exactly which squares have
entanglements. You can determine (with varying levels of
difficulty) that the entanglements are partitioned into
thirteen sets of four squares:

Each square in a set behaves indistinguishably from the others, but still the entanglements don't all behave the same way. Figuring out their exact nature is a little tricky, and might require saturating the rest of the board then experimenting.

As it turns out, each set allows its constituent squares to contain a number of mines from some subset of {0, 1, 2, 3, 4}.

- {4} (i.e. every square in this set is guaranteed to contain a mine)
- {4, 2, 0}
- {4, 1} (ie, either every square has a mine
**or**exactly one square has a mine) - {3, 0}
- {4, 2}
- {4, 3, 0}
- {3, 0}
- {3, 2, 1}
- {2}
- {2, 0}
- {0} (no squares in this set ever contain a mine)
- {4, 2}
- {3}

The bottom row provides a sort order for the
sets. Interpreting the configurations as binary bits (i.e. {4}
= 2^4), the answer to this puzzle can be read
out: **PURITY IN DEATH**. Now try not to think of
how many of your many-worlds alternate selves were purified
while solving this puzzle…