Cramped Passageway

+-- Ground level ---------------------------+
|                                           |
|                     *     *               |
|                    / \   /                |
|                   /   \ /                 |
|            *     *     *                  |
|           / \   /     /                   |
|          /   \ /     /                    |
|         *     *     *     *               |
|          \     \     \   / \              |
|           \     \     \ /   \     <       |
|      *     *     *     *     *     *      |
|     / \   / \           \     \   /       |
|    /   \ /   \           \     \ /        |
|   *     *     *     *     *     *         |
|    \     \         / \   / \              |
|     \     \       /   \ /   \             |
|      *     *     *     *     *        *   |
|       \           \           \        >  |
|        \           \           \          |
|         *     *     *     *     *         |
|              / \     \     \   /          |
|             /   \     \     \ /           |
|      M     *     *     *     *     *      |
|       \   /       \   /       \   /       |
|        \ /         \ /         \ /        |
|         *     *     *     *     *         |
|          \   / \         / \   /          |
|           \ /   \       /   \ /           |
|            *     *     *     *            |
|                   >   /                   |
|                      /                    |
|                     *     *               |
|                      \   /                |
|              <        \ /                 |
|               *        *                  |
|                                           |
+-------------------------------------------+