* The grid itself is symmetrical. I tried my best for symmetry in general, but one of the sets of theme squares is not symmetrically arranged. The other set of theme squares is, as is one of the sets of theme answers.

* In general, unchecked squares, like the center one in this grid, are a no-no for crossword makers. Likewise, two-letter answers are frowned on. I used them anyway; maybe next time, I'll adhere more tightly to the rules of construction.

* There are a few obscure clues, but not, I hope, too many.

* Try not to make too many assumptions about what can and cannot go in a square.

* There are four contradictions in the grid.

* If you're genuinely stumped, it may be possible, depending on your computer, to do what Phoenix does: find the truth by looking at the problem from another angle.

HIDDEN MESSAGE: To read the hidden message, find the four squares where the two answers contradict, and read off each set of two letters, starting from the top-left and working to the bottom-right. Sometimes the letter from the ACROSS answer must be read first, and sometimes the letter from the DOWN answer must be read first.

CONTRADICTIONS:

25A. GUNSHO(T)
6D. EXTR(A)
--
11D. CLOC(K)
27A. THINK(E)R
--
54D. PHO(T)O
70A. (H)AMMERS
--
53D. REVE(A)L
72A. LEA(T)HER

MESSSAGE: TAKE THAT!

Each of these pairs represented something that exposed a critical contradiction in one of first game's cases: the EXTRA GUNSHOT in 1-4, the THINKER CLOCK of 1-1 and 1-2, HAMMER'S PHOTO in 1-3, and the decision to REVEAL the LEATHER in 1-5. Taken together, these cover every case in PW:AA.

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The hidden date is, of course, 12/28, the day of the DL-6 incident, and combo to Yanni Yogi's safe. The two arrows were a clue that the one had to turn the problem around, in a sense, and read the numbers backwards, from lower-right to top-left.

The number clues were admittedly hard, but I used symmetry to make it clear where numbers were, I hope, after the second one.

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Finally, the center squares can also be considered themed: AMI, MIA, IAM, AIM all being things we might see on a certain vase.

THE MOST OBSCURE CLUES, EXPLAINED:

3A. MRME = "Mr. Me," a They Might Be Giants song.
52A. 1RY = Onery. I hoped the counting rhyme's pattern would give it away. "Onery, twoery, tickery tin."

2D. KUDOU = Hiroyuki Kudou, the main GS3 programmer.
5D. MOLCO. Sorry, non-TWEWY players.
12D. BADTR = Bad tr.; bad translation.
26D. H8I = HAITI = I AM SO SORRY.
34D. ATI, graphics card manufacturer. Look, if the NYT Crossword can ask about obscure actors from the fifties, I think I ought to be able to ask who manufactured the Radeon.