$ python3 fifteen.py

Let's play fifteen!
Enter a number to move that square.
Assume the zero is the blank square.
Try to get them all in order (0 1 2 3 on top row, etc).
Enter -1 to quit.

---------------------
|  1 |  2 |  7 | 11 |
---------------------
|  4 |  5 |  3 |  0 |
---------------------
|  8 |  9 |  6 | 10 |
---------------------
| 12 | 13 | 14 | 15 |
---------------------
Your move? 99
Please enter 1-15, or -1 to quit.
Your move? 12
Making move 12...
I'm sorry, Dave. I can't do that move...
==============================
---------------------
|  1 |  2 |  7 | 11 |
---------------------
|  4 |  5 |  3 |  0 |
---------------------
|  8 |  9 |  6 | 10 |
---------------------
| 12 | 13 | 14 | 15 |
---------------------
Your move? zebra
Please enter 1-15, or -1 to quit.
Your move? 10
Making move 10...
==============================
---------------------
|  1 |  2 |  7 | 11 |
---------------------
|  4 |  5 |  3 | 10 |
---------------------
|  8 |  9 |  6 |  0 |
---------------------
| 12 | 13 | 14 | 15 |
---------------------
Your move? -1
quitting...