If you have a vertical line of pit, it will all be shaded dark. If you then place a piece of pit one square to the left of it, the square 3 below it in the vertical line will suddenly be shaded lightly, making it look very out of place. I don't know if there's a(n easy) way to examine this, but here it is none-the-less.
It is true for every tileset that does not have black pits, and is most noticable in the Slime tileset. For a demonstration, just set up some tiles as follows:
P
P
P
PP
P
P
P
P
where the 'P's represent pit squares. the second from the bottom will be shaded lightly.
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Deploy the... I think it's a yellow button... it's usually flashing... it makes the engines go... WHOOSH!
