Although many of you Wolf3D fans probably know about the previous tricks, I really doubt that many of you at all know about this neat little trick. However, if you assign map code 0040 to a tile, on that tile there will be a solid gray-stone wall. The weird thing, though, is that the block has no shading -- all four sides, including the two "vertical" sides, have the "light gray stone" texture. Plus, if the block is made pushable and moves more than one tile in one push, it will disappear. There are a number of things that you can do with this trick, including using it to "disappear and reveal" secret rooms, using it to create puzzles where you have to cause many blocks to disappear so that you can do something, and making it a trap by having a boss or Pac-Man ghost come after you as soon as the block disappears.