Like most platform games, Dangerous Dave uses tiles to save memory and keep footprint small. All levels share the same tile map, which is stored uncompressed in a file called egatiles.dd2. Tiles are stored sequentially, but independent from each other. 16 x 16 pixels, tiles are 4bit and written down in interleaved EGA representation. There is no header in this file, and tiles are not tagged or indexed in any way. In the dump below, you can see that there are 13 tiles across, yielding a width of 208 pixels; it’s a magic number I just guessed, as it brings out something nicely viewable. Grab a quick look at the tiles, and you will see that several tiles are marked with the text ‘free’, others are just empty boxes, and some are even unused in the game.
Levels descriptors are these small files named level%02d.dd2, there are 8 such files, hence only 8 levels. Each file is compressed using RLEW, which is an rle compression that works on 16 bits words.
0000000030: 4A 00 FE FE 27 00 33 00 ? 4A 00 FE FE 04 00 33 00
Quite simple, when hitting a 0xfefe magic, the next word is the count, followed by the value. Replace these 3 words with value x count and you’re done.
Here are the first 0×50 uncompressed bytes from the first level:
0000000000: 20 39 00 00 40 00 39 00 ? 02 00 00 00 00 00 50 00
0000000010: 2a 00 80 1c 80 03 80 36 ? 80 60 81 40 83 80 86 0c
0000000020: 80 04 84 60 33 00 33 00 ? 33 00 33 00 33 00 33 00
0000000030: 33 00 33 00 33 00 33 00 ? 33 00 33 00 33 00 33 00
0000000040: 33 00 33 00 33 00 33 00 ? 33 00 33 00 33 00 33 00
Bytes 0×00 - 0×03: Size of unpacked file (must not be 0xfefe:))
Bytes 0×04 - 0×05: Level width in tiles (16 pixels)
Bytes 0×06 - 0×7: Level height in tiles (16 pixels)
The rest of the level is split into two parts, the visual (rasterable) section, and magic locations (for monsters, start and exit, power-ups and doors.) The two sections are exactly width*height*16bit each. In the visual section, each such 16 bit word represents an index into the linear tile map. Here are some magic numbers from the second section, these values were retrieved via trial and error. I can’t say I spent a lot of time on this, but the idea should be clear:
Tag 0×0001: Zombie
Tag 0×0002: Old lady with a knife
Tag 0×00ff: Player initial location (entry point)
Tag 0×0010: 400 points
Tag 0×0013: 1UP
Tag 0×0633: Teleport 1
Tag 0×0a06: Teleport 2
Tag 0×8001: 100 points inside a closet
The level-to-png.py script rasterizes a level previously unpacked with unpack-level.py. Here is the first level; you may notice that some of tiles are never seen on screen. There’s also a modified copy, which was made using my level editor.
