Castle Wall Instructions

Rules: The challenge is to draw a single loop, without crossings or intersections, subject to the following rules:

1. Bordered unshaded cells and shaded cell do not form part of the loop.
2. Bordered unshaded cells must be inside the loop upon completion.
3. Shaded cells must be outside the loop upon completion.
4. Numbers sum the length of the loop segments in a given direction, each cell border crossed in that direction represents a count of one.