Tunnel

The environment enables the user to typeset Tunnel logic puzzles. Determine the course of the tube. Draw the only possible connection, from the beginning to the end. The numbers indicate how many tube segments (including portals) are present in the corresponding rows and columns. The tube is one cell wide, and does not cross or touch itself!

\begin{center}
  \begin{tunnel}
    \framepuzzle
    \tunnelH{4,3,3,3,4}
    \tunnelV{5,1,5,1,5}
    \portal{1}{1}
    \portal{5}{5}
  \end{tunnel}
  \hspace{1.5cm}
  \begin{tunnel}
    \framepuzzle
    \tunnelH{4,3,3,3,4}
    \tunnelV{5,1,5,1,5}
    \portal{1}{1}
    \portal{5}{5}
    \tube{\tikzpath{1}{1}{6,6,6,6,8,8,4,4,4,4,8,8,6,6,6,6}}
  \end{tunnel}
\end{center}