+-----+-----+-----+-----+-----+-----+-----+-----+-----+
|     |     |     "     |     |     "     |     |     |
|  1  |  3  |  7  "  8  |  2  |  9  "  4 <<< 5 <<< 6  |
|     |     |     "     |  ^  |     "  v  |     |  ^  |
+-----+-----+-----+-----+--^--+-----+--v--+-----+--^--+
|     |     |     "     |  ^  |     "  v  |     |  ^  |
|  9  |  2  |  5  "  6  |  4  |  1  "  3  |  8  |  7  |
|  v  |     |     "     |  ^  |     "  v  |     |  ^  |
+--v--+-----+-----+-----+--^--+-----+--v--+-----+--^--+
|  v  |     |     "     |  ^  |     "  v  |     |  ^  |
|  8  |  4  |  6  "  7  |  5  |  3  "  1  |  2  |  9  |
|  v  |     |  v  "     |  ^  |     "     |     |     |
+==v==+=====+==v==+=====+==^==+=====+=====+=====+=====+
|  v  |     |  v  "     |  ^  |     "     |     |     |
|  7  |  9  |  4  "  3  |  6  |  5  "  2  |  1  |  8  |
|  v  |     |  v  "     |  ^  |     "     |     |     |
+--v--+-----+--v--+-----+--^--+-----+-----+-----+-----+
|  v  |     |  v  "     |  ^  |     "     |     |     |
|  6  |  1  |  3  "  4  |  8  |  2  "  9 >>> 7 >>> 5  |
|  v  |     |  v  "     |     |     "     |     |  v  |
+--v--+-----+--v--+-----+-----+-----+-----+-----+--v--+
|  v  |     |  v  "     |     |     "     |     |  v  |
|  5  |  8  |  2  "  9  |  1  |  7  "  6  |  3  |  4  |
|  v  |     |  v  "     |     |     "     |     |  v  |
+==v==+=====+==v==+=====+=====+=====+=====+=====+==v==+
|  v  |     |  v  "     |     |     "     |     |  v  |
|  4  |  5  |  1  "  2  |  9 >>> 8 >>> 7 >>> 6 >>> 3  |
|  v  |     |     "     |     |     "     |     |  v  |
+--v--+-----+-----+-----+-----+-----+-----+-----+--v--+
|  v  |     |     "     |     |     "     |     |  v  |
|  3  |  6  |  8  "  1  |  7  |  4  "  5  |  9  |  2  |
|  v  |     |     "     |     |     "     |     |  v  |
+--v--+-----+-----+-----+-----+-----+-----+-----+--v--+
|  v  |     |     "     |     |     "     |     |  v  |
|  2  |  7  |  9 >>> 5 >>> 3 <<< 6 <<< 8  |  4  |  1  |
|     |     |     "     |     |     "     |     |     |
+-----+-----+-----+-----+-----+-----+-----+-----+-----+