Underground Tunnel
==================

+-- Level +7 ---------------------------------------------------------------------------------------------------+
|                                                                                                            ^  |
|                                                                                                            %  |
|                                                                                                            v  |
|                                                                                                               |
+---------------------------------------------------------------------------------------------------------------+

+-- Level +6 ---------------------------------------------------------------------------------------------------+
|                                                                                                            ^  |
|                                                                                                            %  |
|                                                                                                            v  |
|                                                                                                               |
+---------------------------------------------------------------------------------------------------------------+

+-- Level +5 ---------------------------------------------------------------------------------------------------+
|                                                                                                            ^  |
|                                                                                                            %  |
|                                                                                                            v  |
|                                                                                                               |
+---------------------------------------------------------------------------------------------------------------+

+-- Level +4 ---------------------------------------------------------------------------------------------------+
|                                                                                                            ^  |
|                                                                                                            %  |
|                                                                                                            v  |
|                                                                                                               |
+---------------------------------------------------------------------------------------------------------------+

+-- Level +3 ---------------------------------------------------------------------------------------------------+
|   ^                                                                                                           |
|   %                                                                                                           |
|   v                                                                                                           |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                            ^  |
|                                                                                                            %  |
|                                                                                                            v  |
|                                                                                                               |
+---------------------------------------------------------------------------------------------------------------+

+-- Level +2 ---------------------------------------------------------------------------------------------------+
|   ^                                                                                                           |
|   %                                                                                                           |
|   v                                                                                                           |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                            ^  |
|                                                                                                            %  |
|                                                                                                            v  |
|                                                                                                               |
+---------------------------------------------------------------------------------------------------------------+

+-- Level +1 ---------------------------------------------------------------------------------------------------+
|   ^                                                                                                           |
|   %                                                                                                           |
|   v                                                                                                           |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                                               |
|                                                                                             *                 |
|                                                                                            / \                |
|                                                                                           /   \               |
|                                                                                 %--*--*--*     *              |
|                                                                                 v               \             |
|                                                                                                  \            |
|                                                                                                   *           |
|                                                                                                    \          |
|                                                                                                     \         |
|                                                                                                      *        |
|                                                                                                       \       |
|                                                                                                        \   ^  |
|                                                                                                         *--%  |
|                                                                                                               |
+---------------------------------------------------------------------------------------------------------------+

+-- Ground level -----------------------------------------------------------------------------------------------+
|                                                                                                               |
|                  *                                                                                            |
|                 / \                                                                                           |
|   ^            /   \                                                                                          |
|   %--*--*--*--*     *           *                                                                             |
|                      \         / \                                                                            |
|                       \       /   \                                                                           |
|                        *--*--*     %                                                                          |
|                                    v                                                                          |
|                                                                                                               |
|                                                                           %--*                                |
|                                                                           v   \                               |
|                                                                                \^                             |
|                                                                                 %                             |
|                                                                                  \                            |
|                                                                                   \                           |
|                                                                                    *                          |
|                                                                                                               |
+---------------------------------------------------------------------------------------------------------------+

+-- Level -1 ---------------------------------------------------------------------------------------------------+
|                                                                                                               |
|                                             *                                                                 |
|                                            / \                                                                |
|                                           /   \                                                               |
|                                          *     *                                                              |
|                                         /       \                                                             |
|                                    ^   /         \                                                            |
|                                    %--*           *                                                           |
|                                                    \                                                          |
|                                                     \                     ^                                   |
|                                                      *                    %                                   |
|                                                       \                  /                                    |
|                                                        \                /                                     |
|                                                         *--*--*--*--*--*                                      |
|                                                                                                               |
+---------------------------------------------------------------------------------------------------------------+