When placing a ladder in a single empty cell with all adjacent cells containing blocks, the cell becomes unnaturally dark. The dark area does not seem to occur if there is another empty cell beside the placed ladder. The dark area seems quite inconsistent with the way environments are naturally lit up. I can duplicate the bug by simply digging a short way into some rock, digging a single block directly above my character and then placing a ladder in to it. It only seems to occur for cells directly above the character. I have attached some images to illustrate (the second image is after I dug the adjacent block, after which the cell returned to normal).