In the Penrose grid, each enclosed polygon has four sides, but the number of lines that meet at each dot varies (in most cases three or five lines meet at each point). Where three lines meet, things are quite easy (as soon as you have ruled out two lines, the third is ruled out). You need to be more careful where five lines meet. It is easy to assume that ruling out three lines means the slitherlink loop does not pass through that point, but you have to rule out 4 of the 5 before that is the case.
To work out the location of this cache, you need to do the following:
- Solve the puzzle below (see the cache listing for Slitherlink Boot Camp for the rules about how to solve Slitherlink puzzles).
- Locate the letters a through to t in the puzzle (o and l are omitted). For each letter, its numeric value is the number of lines around the cell (which means each value is between 0 and 3).
The cache can be found at S 43 31.ABC E 172 33.DEF, where:
A = a + b + c
B = d + e + f
C = g + h + i
D = j + k + s
E = m + n + t
F = p + q + r
The checksum for A to F is 30.
The cache is a small capsule embedded in a block of wood, tucked behind a post (the one at the end of the fence). Should be easy to spot and retrieve from the footpath. Stealth needed; GZ is a bit exposed.