|                           |
         -------                     ---|---
            |                           |
(Horizontal segment on top)   (Vertical segment on top)

+-------+    +-------+
|       |    |       |
|   +---|----+   +-------+
|   |   |        |   |   |
+-------|------------|---+
    |   |        |   |
    +---+        +---+

KNOT

+----------+
|          |
|    +--------------+
|    |     |        |
|    |   +-|----+   |
|    |   | |    |   |
|    +-----+    |   |
|        |      |   |
|        +------|---+
|               |
+---------------+

NOT

+-----------+
|           |
|           | +-------+
|           | |       |
| +-------+ | |       |
| |       | | |       |
| |     +---+ |       |
| |     | |   |       |
| |     | +---+       |
| |     |             |
| |     |       +-------+
| |     |       |     | |
+-----+ |       |     | |
  |   | |       |     | |
  | +---+       |     | |
  | | |         |     | |
  | | +-------------+ | |
  | |           |   | | |
  | |           | +---+ |
  | |           | | |   |
  | |           | | +---+
  | |           | |
  +-+           | |
                | |
                +-+

(5,10, 1,9, 8,10, 9,12, 5,12, 1,4, 0,3, 2,4, 3,7, 6,8, 7,11, 2,11, 0,6)

$ python3 knot.py <<EOF
+-------+    +-------+
|       |    |       |
|   +---|----+   +-------+
|   |   |        |   |   |
+-------|------------|---+
    |   |        |   |
    +---+        +---+
EOF
KNOT
$ python3 knot.py <<EOF
+----------+
|          |
|    +--------------+
|    |     |        |
|    |   +-|----+   |
|    |   | |    |   |
|    +-----+    |   |
|        |      |   |
|        +------|---+
|               |
+---------------+
EOF
NOT
$ python3 knot.py <<EOF  # the Culprit
        +-----+
        |     |
+-----------+ |
|       |   | |
|   +-+ | +---|-+
|   | | | | | | |
| +-|-------+ | |
| | | | | |   | |
+-|-+ | | +---+ |
  |   | |       |
  +---|---------+
      | |
      +-+
EOF
NOT
$ python3 knot.py <<EOF  # Ochiai unknot
    +-----+
    |     |
  +-|---------+
  | |     |   |
  | | +-+ |   |
  | | | | |   |
+-|-|---|-|-+ |
| | | | | | | |
| | | +---|---+
| | |   | | |
+-------+ | |
  | |     | |
  | +-------+
  |       |
  +-------+
EOF
NOT
$ python3 knot.py <<EOF  # Ochiai unknot plus trefoil
    +-----+ +-----+
    |     | |     |
  +-|---------+   |
  | |     | | |   |
  | | +-+ | +---+ |
  | | | | |   | | |
+-|-|---|-|-+ +---+
| | | | | | |   |
| | | +---|-----+
| | |   | | |
+-------+ | |
  | |     | |
  | +-------+
  |       |
  +-------+
EOF
KNOT
$ python3 knot.py <<EOF  # Thistlethwaite unknot
      +---------+
      |         |
    +---+ +---------+
    | | | |     |   |
    | +-------+ |   |
    |   | |   | |   |
    |   | | +---+   |
    |   | | | |     |
    |   | +-------+ |
    |   |   | |   | |
    |   +-------+ | |
    |       | | | | |
+-----------+ | | | |
|   |         | | | |
| +-----------+ | | |
| | |           | | |
| | +-------------+ |
| |             |   |
| |             +-----+
| |                 | |
| |                 +---+
| |                   | |
+---------------------+ |
  |                     |
  +---------------------+
EOF
NOT
$ python3 knot.py <<EOF  # (−3,5,7)-pretzel knot
      +-------------+
      |             |
    +-|-----+       |
    | |     |       |
  +-|-+   +-------+ |
  | |     | |     | |
+-|-+   +---+   +---+
| |     | |     | |
| |   +---+   +---+
| |   | |     | |
| | +---+   +---+
| | | |     | |
| +---+   +---+
|   |     | |
|   |   +---+
|   |   | |
|   | +---+
|   | | |
|   +---+
|     |
+-----+
EOF
KNOT
$ python3 knot.py <<EOF  # Gordian unknot
+-------------+                 +-------------+
|             |                 |             |
| +---------+ |                 | +---------+ |
| |         | |                 | |         | |
| | +-------------+         +-------------+ | |
| | |       | |   |         |   | |       | | |
| | | +---------+ |         | +---------+ | | |
| | | |     | | | |         | | | |     | | | |
| +-------+ | +-------+ +-------+ | +-------+ |
|   | |   | |   | |   | |   | |   | |   | |   |
+-------+ | +-------+ | | +-------+ | +-------+
    | | | |     | | | | | | | |     | | | |
    | +-------+ | | | | | | | | +-------+ |
    |   | |   | | | | | | | | | |   | |   |
    +-------+ | | | | | | | | | | +-------+
        | | | | | | | | | | | | | | | |
        | +-----+ | | | | | | +-----+ |
        |   | |   | | | | | |   | |   |
        +---------+ | | | | +---------+
            | |     | | | |     | |
          +---------+ | | +---------+
          | | |       | |       | | |
          | | +-----------------+ | |
          | |         | |         | |
          | +---------------------+ |
          |           | |           |
          +-----------+ +-----------+
EOF
NOT