You might also add the condition that best-move(deep-search) != best-move(shallow-search). IMO this is what really makes a move surprising - it looks bad, but

You might also add the condition that best-move(deep-search) != best-move(shallow-search). IMO this is what really makes a move surprising - it looks bad, but is good. Btw, I've never seen Rxd4!! from Kasparov-Topalov described as a "natural" move. I'm guessing the author meant "unnatural". :)