We agree on the format. I had the map thing figured out, but since I already have map ripped I don't need it. The info of the tiles stored in BITS1A.PI1 is interesting though (only if we can figure out the demo tile format)
I looked very deeply in the demo data, PC or Amiga and no luck for the tilemap. Rest of the info is similar to the full version (walls/ladders/...) & items. Puzzling! I think the tile part is unpacked later once the file has been unpacked "generically". But maybe you checked WinUAE memory and had no luck.
I attach the "unpacked" amiga tilemap for demo.
@booboo: the format is:
round 0x10: tiledata (demo: the internal format of which we don't know, full: easy 0x2000 tile matrix data)
round 0x2000: wall/ladder data (simple, see qube's post)
round 0x4000: object & monsters coords & types (only the visible ones)
after that I don't know...