Early thoughts on [LAYR]DATA: there doesn't seem to be any equivalent of the dictionary/words found in .j2l files. Instead, the layers (the ones that have tiles, at least -- just like in .j2l files, it looks like layers without tiles do not have their empty contents saved at all) are laid out pretty much short by short, but with some data missing. In the only level I've looked at in any detail (TREASUR1, chosen because it has no foreground layers) instances of sixteen consecutive blank tiles are not included. So far I haven't figured out where in the file it indicates where those blocks of sixteen need to be inserted. Also it looks like layers with Tile Width whose widths are not multiples of 4 16 may get some padding, but that's a very tentative result so far. Haven't run across any flipped or animated tiles yet.