Mr. Code

In today's episode of "What Vic Was Doing When His Computer Was Being Repaired": the semi-complicated code grid.
I actually had been planning something like this for a long time, but figured it was too much stress to come up with a different symbol for every pair of letters in the alphabet and not have some look too similar. Anyhow, that film Zodiac came out a few weeks ago, so there were some docs on the TV about the case and investigation (involving codes) that I watched. I decided to give this another try, as I hadn't much else to do.
Of course, it became clear that it wasn't necessary to make a symbol for EVERY possible digraph, and just settled for the thirteen most common letters, and blacked out the more obscure pairs.
I'm probably not gonna use this for anything, but I guess it's another one things I did just to see if I could finish it.