Castle Wall Description

Castle Wall is a puzzle original to this blog to the best of my knowledge. Some cells contain a number and arrow; these cells are either white or black. The object is to draw a single closed loop passing through adjacent squares. Squares with a number and arrow in them may not be included in the loop. All of the black cells must be outside of the loop, and all of the white cells must be inside of the loop. Furthermore, if a cell has a left or right arrow, the number in that cell tells the total length of horizontal segments in the arrow’s direction. Likewise, if there is an up or down arrow, the number tells the total length of vertical segments. Equivalently, the number tells how many boundaries in the arrow’s direction are crossed by the path. The solution is unique.

Below is an example puzzle and its only solution.

Additional features:

• Some clue squares will not have a number and an arrow and instead merely have a color or, if white, a thicker border. The color of these squares indicates whether they are inside or outside the loop.