+-- Ground level -----------------------------------+
| |
| M |
| | |
| | |
| * |
| / |
| / |
| * |
| \ |
| \ |
| * * * |
| \ | / |
| \ | / |
| * *--* * |
| \ / / |
| \ / / |
| * * * |
| \ | / |
| \ & / |
| *--*--*--*--*--* |
| / | \ |
| / | \ |
| * * * * |
| / \ \ / \ |
| / \ \ / \ |
| * *--*--* * * |
| / \ \ |
| / \ \ |
| * * * |
| / | \ |
| / | \ |
| * * M |
| | |
| | |
| * |
| \ |
| \ |
| *--* * |
| \ | |
| \ | |
| *--* *--*--* |
| \ \ | |
| \ \| |
| * * * * * |
| | \ / | |
| | \ / | |
| * * * *--*--* |
| \ \ | | |
| \ \ | | |
| * * * * * * |
| \ /| / \ / \ / \ \ |
| \ / |/ \ / \ / \ \ |
| * * * *--* *--* *--* |
| / | | \ / |
| / | | \ / |
| * * * *--* |
| v / |
| / |
| * |
| |
+---------------------------------------------------+